COVID-19 (coronavirus disease 2019) is a disease caused by a virus called SARS-CoV-2. There are two types of tests for this virus:

• A viral test tells you if you have a current infection. Viral tests can either be rapid tests or laboratory tests:
  • Rapid tests can be done in minutes. They are often antigen tests, which look for specific proteins from the virus. Some rapid tests are self-tests which you can do at home.
  • Laboratory tests can take days to complete and include PCR tests.
• An antibody (serology) test might tell you if you had a past infection.

If you need a COVID-19 test, you can:

• Buy a self-test online or at a store. Make sure that the test you buy has been authorized by the U.S. Food and Drug Administration (FDA).
• Check your state or local health department's website for information on testing in your area.
• Contact your health care provider.
• Order free self-tests from COVID.gov for your household, if you live in the U.S. The tests are from the U.S. government.

Even if your COVID-19 viral test is negative (the test did not detect the virus), you should still take steps to protect yourself and others.

COVID-19 testing plays a critical role in the fight against the virus. Understanding COVID-19 tests, including the different types of tests and their uses, and the types of samples the tests use, is key to making an informed decision that meets your needs.

Types of Tests

There are different types of COVID-19 tests – diagnostic tests and antibody tests.

Diagnostic tests can show if you currently are infected with SARS-CoV-2, the virus that causes COVID-19. There are two common types of COVID-19 diagnostic tests:

• Molecular tests, such as polymerase chain reaction (PCR) and other nucleic acid amplification tests (NAATs) tests, which detect genetic material called RNA from the virus
• Antigen tests, often referred to as rapid tests or, for some, at-home or self tests, which detect proteins called antigens from the virus

Samples for COVID-19 diagnostic tests are typically collected using an anterior nares (nasal) swab sample. Some diagnostic tests use other samples such as mid-turbinate, nasopharyngeal, oropharyngeal, or saliva samples. Depending on the intended use, COVID-19 diagnostic tests can be performed at a laboratory, a standalone testing site, a doctor’s office or health clinic, or at home. For most molecular COVID-19 diagnostic tests, you go to a testing site to have your sample collected and for others you can collect your own sample at home using a home collection kit and mail it to a laboratory for testing. Some tests, including most antigen tests, can be performed completely at home, giving you results within minutes, without needing to send your sample to a laboratory.

If you think you need a COVID-19 diagnostic test, you can find a community testing site in your state. You can also use an FDA-authorized at-home COVID-19 diagnostic test which gives you the option of self-testing where it is convenient for you. Be sure to check the At-Home OTC COVID-19 Diagnostic Tests website for information on expiration dates, who can use the test, and other details that may help you decide what test is right for you. Be aware that COVID-19 diagnostic tests are authorized for specific uses and that laboratory-based molecular COVID-19 tests, are generally more accurate than at-home tests.

To increase the accuracy of an at-home COVID-19 antigen diagnostic test, it is important to perform repeat testing, after 48 hours, following a negative test result, whether you have symptoms or not, to reduce your risk of a false negative test result. For more information about how to reduce your risk of getting a false negative result on an at-home COVID-19 antigen test, read our FDA Safety Communication. For additional information on reading and understanding your test results, see Understanding At-Home OTC COVID-19 Antigen Diagnostic Test Results.

For details about each authorized COVID-19 diagnostic test, see the lists of authorized Molecular Diagnostic Tests and Antigen Diagnostic Tests, as well as the At-Home COVID-19 Diagnostic Tests webpage. Using the search box in the EUA tables, you can use keywords to search and filter the type of test or collection kit you are looking for. As new tests are authorized for use, they are added to these tables so that anyone can access up-to-date information on all authorized tests and collection kits.

Antibody (or serology) tests look for antibodies in your blood that your immune system produced in response to SARS-CoV-2, the virus that causes COVID-19. Antibody tests should not be used to diagnose a current SARS-CoV-2 infection or COVID-19 and, at this time, should also not be used to check for immunity. More research is needed to determine what, if anything, antibody tests can tell us about a person’s immunity.

Samples for antibody tests are typically collected by a doctor or other medical professional by taking blood from a finger stick or your vein. For more information about antibody testing, visit Antibody (Serology) Testing for COVID-19: Information for Patients and Consumers.

Types of Samples

Different tests are authorized to be used with different types of samples. The most common sample types are:

Swab samples use a swab (similar to a long Q-Tip) to collect a sample from the nose or throat. The types of samples include:

• Anterior Nares (Nasal) – takes a sample from just inside the nostrils
• Mid-turbinate – takes a sample from further up inside the nose
• Nasopharyngeal – takes a sample from deep inside the nose, reaching the back of the throat, and should only be collected by a trained health care provider
• Oropharyngeal – takes a sample from the middle part of the throat (pharynx) just beyond the mouth, and should only be collected by a trained health care provider

Saliva samples are collected by spitting into a tube rather than using a nose or throat swab.

Blood samples are only used to test for antibodies and not to diagnose COVID-19. Venous blood samples are typically collected at a doctor’s office or clinic. Some antibody tests use blood samples from a finger stick.

Beginning with the Human Genome Project 30 years ago, NHGRI has supported research that reduced the cost and increased the speed of genetic and genomic sequencing, enabling the rapid pivot towards COVID-19 research and development. NHGRI’s investments in DNA-sequencing and related technologies created a foundation that allowed companies to rapidly deploy COVID-19 PCR diagnostic testing early in the pandemic.

Key Points:

• Genomic research has been central to understanding and combating the SARS-CoV-2 (COVID-19) pandemic.
• Polymerase chain reaction (PCR) is a laboratory technique that uses selective primers to “copy” specific segments of a DNA sequence.
• COVID-19 PCR tests use primers that match a segment of the virus’s genetic material. This allows many copies of that material to be made, which can be used to detect whether or not the virus is present.
• A positive COVID-19 PCR test means that SARS-CoV-2 is present. A negative result could either mean that the sample did not contain any virus or that there is too little viral genetic material in the sample to be detected.

What is PCR?

Polymerase chain reaction (PCR) is a common laboratory technique used in research and clinical practices to amplify, or copy, small segments of genetic material. PCR is sometimes called “molecular photocopying,” and it is incredibly accurate and sensitive. Short sequences called primers are used to selectively amplify a specific DNA sequence. PCR was invented in the 1980s and is now used in a variety of ways, including DNA fingerprinting, diagnosing genetic disorders and detecting bacteria or viruses. Because molecular and genetic analyses require significant amounts of a DNA sample, it is nearly impossible for researchers to study isolated pieces of genetic material without PCR amplification.

How does COVID-19 PCR testing work?

COVID-19 testing uses a modified version of PCR called quantitative polymerase chain reaction (qPCR). This method adds fluorescent dyes to the PCR process to measure the amount of genetic material in a sample. In this instance, healthcare workers measure the amount of genetic material from SARS-CoV-2.

The testing process begins when healthcare workers collect samples using a nasal swab or saliva tube. The SARS-CoV-2 virus, which is the pathogen that causes COVID-19, uses RNA as its genetic material. First, the PCR is converted from single-stranded RNA to double-stranded DNA in a process called reverse transcription. The two DNA template strands are then separated.

Primers attach to the end of these strands. Primers are small pieces of DNA designed to only connect to a genetic sequence that is specific to the viral DNA, ensuring only viral DNA can be duplicated (right). After the primers attach, new complementary strands of DNA extend along the template strand. As this occurs, fluorescent dyes attach to the DNA, providing a marker of successful duplication. At the end of the process, two identical copies of viral DNA are created. The cycle is then repeated 20-30 times to create hundreds of DNA copies corresponding to the SARS-CoV-2 viral RNA.

What do results mean for a COVID-19 PCR test?

A positive result happens when the SARS-CoV-2 primers match the DNA in the sample and the sequence is amplified, creating millions of copies. This means the sample is from an infected individual. The primers only amplify genetic material from the virus, so it is unlikely a sample will be positive if viral RNA is not present. If it does, it is called a false positive.

A negative result happens when the SARS-CoV-2 primers do not match the genetic material in the sample and there is no amplification. This means the sample did not contain any virus.

A false negative result happens when a person is infected, but there is not enough viral genetic material in the sample for the PCR test to detect it. This can happen early after a person is exposed. Overall, false negative results are much more likely than false positive results.

Antibodies are developed by the body in response to an infection or after vaccination. SARS-CoV-2 is the virus that causes COVID-19. SARS-CoV-2 antibody tests detect antibodies to the SARS-CoV-2 virus. SARS-CoV-2 antibody tests can help identify people who may have been infected with the SARS-CoV-2 virus or have recovered from COVID-19. Antibody tests should not be used to tell you if you have an active COVID-19 infection.

Scientists continue to learn more about COVID-19 and COVID-19 immunity. At this time, SARS-CoV-2 antibody tests do not tell you if:

• You currently have COVID-19, the disease caused by the SARS-CoV-2 virus,
• You have immunity that will prevent COVID-19,
• You need a COVID-19 vaccine, or
• Your COVID-19 vaccine worked.

Antibodies and Antibody Tests: The Basics

Q: What are antibodies?

A: Antibodies are proteins made by your body's immune system to help fight off infections, including those caused by viruses. Some antibodies in your body may protect you from getting those infections. Your immune system can also safely learn to make antibodies through vaccination. If antibodies give you this protection and how long this protection lasts can be different for each disease and each person. Antibodies are just one part of your immune response.

Q: Are antibody tests used to diagnose COVID-19?

A: No. An antibody test cannot be used to diagnose current COVID-19 because an antibody test does not detect SARS-CoV-2. Only COVID-19 diagnostic tests can be used to diagnose current COVID-19. A positive antibody test result can be used to help identify people who may have had a prior SARS-CoV-2 infection or prior COVID-19. An antibody test does not show if you have a current SARS-CoV-2 infection or COVID-19 because the antibodies are part of the body's immune response to infection, and antibody tests do not test for the virus itself. It also can take days to weeks after the infection for your body to make detectable antibodies.

Antibody Tests: Not for Use to Check Immunity

Q: Will a positive result on a SARS-CoV-2 antibody test mean I have immunity and I will not get COVID-19?

A: No. At this time, SARS-CoV-2 antibody tests do not tell you if you have immunity that will prevent you from getting COVID-19. A positive SARS-CoV-2 antibody test does not necessarily mean you are immune or have immunity that will prevent COVID-19. More research is needed to understand what SARS-CoV-2 antibody test results can tell us. And, SARS-CoV-2 antibodies detected in your blood reflect only one part of your immune system, which also includes T-cells and other components that are part of your body's immune response.

Q: Should I get a SARS-CoV-2 antibody test to decide if I need a COVID-19 vaccine or after I am vaccinated to see if my vaccine worked?

A: No. At this time, antibody test results should not be used to decide if you need a COVID-19 vaccine or a vaccine booster, or to determine whether your vaccine worked. There is not a clear connection between SARS-CoV-2 antibody test results, the need for a COVID-19 vaccine or booster, or whether a vaccine worked in a person. Also, some SARS-CoV-2 antibody tests may not detect the kind of antibodies created following vaccination. SARS-CoV-2 antibodies detected in your blood reflect only one part of your immune system, which also includes T-cells and other components that are part of your body's immune response.

More research is needed to understand the role of SARS-CoV-2 antibody testing in evaluating a person's immunity or protection against COVID-19 and understanding if antibody tests will be helpful for deciding if a person should receive a COVID-19 vaccine. If you have questions about whether a SARS-CoV-2 antibody test is right for you, talk with your health care provider or your state or local health department.

Q. Can a SARS-CoV-2 antibody test tell me if I could infect other people?

A: No. Antibody tests do not tell you whether or not you can infect other people with SARS-CoV-2. Current information indicates people infected with SARS-CoV-2 can still transmit the SARS-CoV-2 virus and infect other people, even if they are COVID-19 vaccinated or have detectable SARS-CoV-2 antibodies from a previous infection.

Antibody Tests: Results and Terms

Q: What does a positive SARS-CoV-2 antibody test result mean?

A: A positive antibody test result could mean you previously had a SARS-CoV-2 infection or COVID-19. A positive antibody test could also mean the test is detecting antibodies in your blood in response to your COVID-19 vaccine. Not all SARS-CoV-2 antibody tests will detect antibodies in response to a COVID-19 vaccine.

Q: What does a negative SARS-CoV-2 antibody test result mean?

A: A negative result on a SARS-CoV-2 antibody test means antibodies to the virus were not detected in your blood.

It is unknown if all people who have a SARS-CoV-2 infection will develop antibodies in their bodies in an amount that can be detected by a SARS-CoV-2 antibody test. Also, even if people do develop antibodies, the antibody levels may decrease over time to levels that can't be detected by a SARS-CoV-2 antibody test. It is also important to note that different antibody tests may detect different antibodies and different levels of antibodies.

A negative result could mean:

• You have not been infected with SARS-CoV-2 previously.
• You had a previous SARS-CoV-2 infection but:
  • Your body did not make antibodies to the infection yet. It can take days to weeks after an infection for your body to make antibodies.
  • Your body made SARS-CoV-2 antibodies but the level of antibodies in your sample is too low to be measured by the test that was used.
• You were vaccinated with a COVID-19 vaccine, but the antibody test does not detect the same kind of antibodies your body produced in response to your COVID-19 vaccine.
• The test result may be wrong, known as a "false negative." This occurs when the test does not detect antibodies even though you may have antibodies for SARS-CoV-2.

Q: What if I get different results on two SARS-CoV-2 antibody tests and they don't agree? Which one is right?

A: Results may be different for several reasons, including:

• The design of the tests - different antibody tests may detect different antibodies and different levels of antibodies.
• The performance of the tests, including the sensitivity and specificity of each test.
• The timing of when you took the tests, how long it may take for your body to develop antibodies after a potential SARS-CoV-2 infection, and whether antibody levels may decrease over time.

For this and other reasons, you should always review your test results with your health care provider.

Q: What is the difference between qualitative, quantitative, and semi-quantitative SARS-CoV-2 antibody tests? What do the reported numbers mean?

A: Qualitative, semi-quantitative, and quantitative tests all tell you if SARS-CoV-2 antibodies were detected in your blood sample with the specific test used. These tests report whether SARS-CoV-2 antibodies were detected or not detected over a certain threshold, and this threshold may vary between different SARS-CoV-2 antibody tests. Different antibody tests may also be designed to detect different SARS-CoV-2 antibodies in addition to the different levels of antibodies. This means that different tests may provide different results for the same blood sample.

• Qualitative SARS-CoV-2 antibody tests only report whether SARS-CoV-2 antibodies were detected or not detected and do not provide any indication of the amount of antibodies detected, other than whether it was above or below the detection threshold for that test.
• Semi-quantitative SARS-CoV-2 antibody tests also report the relative concentration of antibodies in a person's blood sample at the time of testing, meaning the level of antibody in your blood sample is assigned a number on a scale that applies only to that specific authorized test. The scale for each test is determined and validated by the test developer but is not comparable to results from any other SARS-CoV-2 antibody test, whether semi-quantitative or otherwise.
• Quantitative SARS-CoV-2 antibody tests produce results that are standardized because quantitative antibody tests are traceable to a certified reference material. This means that numeric results can be compared between different quantitative tests that are traceable to the same certified reference material. However, at this time, there is not enough scientific information to understand what the numerical results mean about an individual's protection from infection.

Q: What do sensitivity and specificity mean in SARS-CoV-2 antibody testing?

A: Sensitivity is the ability of the test to identify people with antibodies to SARS-CoV-2. A highly sensitive test will identify most people who truly have antibodies, and a small number of people with antibodies may be missed by the test (false negatives).

Specificity is the ability of the test to correctly identify people without antibodies to SARS-CoV-2. A highly specific test will identify most people who truly do not have antibodies, and a small number of people without antibodies may be identified as having antibodies by the test (false positives).

Q: What does predictive value mean in SARS-CoV-2 antibody testing?

A: Predictive values are probabilities calculated using a test's sensitivity and specificity, and an assumption about the percentage of individuals in the population who have antibodies at a given time (which is called "prevalence" in these calculations).

Positive predictive value is the probability that a person who has a positive test result truly has antibodies. Positive predictive values for SARS-CoV-2 antibody tests are impacted by how common SARS-CoV-2 antibodies are in the population being tested at a certain time.

The lower the prevalence, the lower the positive predictive value. This means that SARS-CoV-2 antibody tests used in areas with low prevalence (small number of people that have SARS-CoV-2 antibodies) will have a positive predictive value lower than in an area with higher prevalence.

Low positive predictive value may lead to more individuals with a false positive result. This could mean that individuals may not have developed antibodies to the virus even though the test indicated that they had. If a high positive predictive value cannot be achieved with a single test result, two tests may be used together to help identify individuals who may truly be SARS-CoV-2 antibody positive.

Negative predictive value is the probability that a person who has a negative test result truly does not have antibodies. Negative predictive values for SARS-CoV-2 antibody tests are also impacted by how common SARS-CoV-2 antibodies are in the population being tested at a certain time. Negative predictive value is higher in areas with low prevalence and lower in areas with high prevalence. This means that in areas where a lot of people have SARS-CoV-2 antibodies, a negative result is more likely to be a false negative result compared to the likelihood of a false negative result in areas where few people have SARS-CoV-2 antibodies. This could mean that individuals may have developed antibodies to the virus even though the test indicated that they had not.

What is a Self-Test or At-Home Test?

Self-tests for COVID-19 give rapid results and can be taken anywhere.

• Self-tests detect current infection and are sometimes also called “home tests,” “at-home tests,” or “over-the-counter (OTC) tests.”
• They give you results in 10-15 minutes and are usually antigen tests. These are different from laboratory-based PCR tests or self-collected samples that are sent to a laboratory; these may take days to return your result.
• Although self-tests are usually faster, they are not as good at detecting the virus as PCR tests, meaning you might get a false negative result.
  • FDA recommends people who get an initial negative result on an antigen test, take at least one more test 48 hours later. Take a third test, 48 hours after the second, if the second test was negative and you don’t have symptoms. Self-tests are more likely to detect the virus if you have symptoms.
  • You may get a PCR test as an alternative to repeat testing.
• Self-tests, along with vaccination and prevention actions, can help you protect yourself and others.

When To Take an At-Home COVID-19 Test

*You may get a PCR test as an alternative to repeat testing.

Testing can be helpful even when you don’t have symptoms or a recent exposure to COVID-19, such as before an event or visiting someone. Test as close to the time of the event as possible (at least within 1-2 days) to help you make informed decisions about your health and your risk of spreading COVID-19 to others.

How to Get an At-Home COVID-19 Test

• Order Four (4) free at-home COVID-19 tests available for U.S. households through the federal government at COVID.gov/tests.
• Buy tests online or in pharmacies and retail stores. Private health insurance may reimburse the cost of purchasing self-tests. Visit FDA’s website for a list of authorized tests.
• Contact your local health department to find out about the availability of free tests.
• If you’re not able to obtain a self-test when you need it, you might also visit a community testing site, or contact a healthcare provider for more options.

How to Use an At-Home COVID-19 Test

Read the complete manufacturer’s instructions for use before using the test.

• Wash your hands before and after you collect a nasal specimen for your test.
• To use an at-home test, you will collect a nasal specimen and then test that specimen.
• If you do not follow the manufacturer’s instructions, your test result may be incorrect.
• The manufacturer may have extended the expiration date for your self-test. Please check the manufacturer’s website to confirm the expiration date, if needed.

What Your Test Results Mean

If Your Test Is Positive

A positive COVID-19 test means the virus was detected and you have an infection.

• Isolate and take precautions, including wearing a high-quality mask to protect others from getting infected.
• Tell people you had recent contact with that they may have been exposed.
• Monitor your symptoms. If you have any emergency warning signs, seek emergency care immediately.
• Contact a healthcare provider, community health center, or pharmacy to learn about treatment options that may be available to you. Treatment must be started within several days after you first develop symptoms to be effective.
  • You are more likely to get very sick if you are an older adult or have an underlying medical condition. Treatment is available. Talk with your healthcare provider to determine what is the best option for you.

If Your Test Is Negative

A negative COVID-19 test means the test did not detect the virus, but this doesn’t rule out that you could have an infection. See FDA instructions on repeat testing.

• If you have symptoms:
  • You may have COVID-19, but tested before the virus was detectable.
  • You may have another viral infection or illness that you need to get tested for. For many diseases, including flu, early diagnosis and prompt treatment is important for preventing severe illness.
  • Take everyday preventive actions to prevent spreading an illness to others.
  • Contact a healthcare provider if you have any questions about your test result or if your symptoms worsen.
• If you do not have symptoms, but were exposed to the virus that causes COVID-19, you should continue to take recommended steps after exposure.
• If you do not have symptoms and have not been exposed to the virus that causes COVID-19, continue to take steps to protect yourself and others, including monitoring for symptoms. Get tested again if symptoms appear.

Related Questions

Should I trust the results of a self-test?

Positive results from self-tests are highly reliable.

Negative results from self-tests don’t rule out that you could have an infection.

Invalid results from self-tests mean the test did not work properly, and you need to take a new test to get an accurate result.

Do I need to report the results from my self-test?

CDC strongly encourages everyone who uses a self-test to report any positive results to their healthcare provider. COVID-19 home tests can be safely and privately reported at MakeMyTestCount.org. Healthcare providers can ensure that those who have tested positive for COVID-19 receive the most appropriate medical care, including specific treatments if necessary.

In certain jurisdictions, healthcare providers who diagnose COVID-19 are required to report those cases to public health.

At-home over-the-counter (OTC) COVID-19 antigen tests, often referred to as rapid tests, detect proteins called antigens from SARS-CoV-2, the virus that causes COVID-19. At-home COVID-19 antigen tests are less likely to detect the SARS-CoV-2 virus than molecular tests, such as polymerase chain reaction (PCR) tests and other nucleic acid amplification tests (NAATs), which detect genetic material called RNA from the virus. This is especially true early in an infection or in people who do not have COVID-19 symptoms. Currently, all at-home COVID-19 antigen tests that are FDA-authorized are authorized for repeat testing, also called serial testing. This means people who receive a negative test result should use multiple tests over a certain period, testing at least twice over three days if they have symptoms and at least three times over five days if they do not have symptoms.

When You Should Test for COVID-19

• If you have symptoms, test immediately and then test again per the instructions if your first result is negative.
• If you were exposed to someone who has COVID-19 and you do not have symptoms, wait at least 5 full days after your exposure before testing. If you test too early, you may have an inaccurate result.
• If you are in certain high-risk settings, you may need to test as part of a screening testing program.
• Consider testing before coming into contact with someone who has a high risk for severe COVID-19; people who are older adults or immunocompromised, or have other medical conditions, especially if you are in an area with a medium or high COVID-19 Hospital Admission Level.

What Your At-Home OTC COVID-19 Test Result Means

Most FDA-authorized at-home OTC COVID-19 tests are antigen tests. While not perfect, they provide a fast and convenient COVID-19 testing option to detect the virus, so you may know if you are infected and should stay at home and away from people to help reduce the spread of the virus.

• A positive result using an at-home COVID-19 antigen test means you likely have COVID-19. Anyone who tests positive for COVID-19, or who likely has COVID-19, should contact their health care provider and follow the CDC's guidelines for staying at home and away from people.
• A negative result using at-home COVID-19 antigen test means the test did not detect the virus that causes COVID-19, but it does not rule out COVID-19 because some tests may not detect the virus early in an infection. Always do a repeat test at minimum after 48 hours following a negative test result when using an antigen test. Use the following guidance to help interpret your negative test result and determine what steps to take next.

In addition to COVID-19 test results, and when determining the likelihood of having the virus, consider:

• Recent symptoms
• Close contact with someone who has COVID-19
• The level of COVID-19 in your community

See more information about negative test results from at-home COVID-19 antigen test and repeat testing below.

What At-home COVID-19 Antigen Tests Do Not Tell You

• If you have an infection immediately after you are exposed to COVID-19 because it may take 2 to 5 days, and sometimes longer, for the virus to be detected by a COVID-19 antigen test. How long it takes before a test can detect the virus may vary between different COVID-19 variants and different tests.
• How contagious you are or if you can spread the virus to someone else. There are no tests that can tell you that. You could pass COVID-19 to others even before you get a positive result on a test.
• If you have another type of respiratory illness, such as flu or respiratory syncytial virus (RSV), unless it is a test specifically authorized for detection of these viruses.

Reporting Your Test Result

The FDA encourages you to voluntarily and anonymously report your positive or negative test results every time you use an at-home COVID-19 test. You can send your test result to MakeMyTestCount.org or use an app or other digital option for self-reporting that may be included with your test. Report each test result one time.

The data from MakeMyTestCount.org can help public health departments know how fast the virus is spreading. This valuable test data help public health departments assess and modify their response to COVID-19 in their local communities, states, or across the country. The MakeMyTestCount website is developed through the National Institutes of Health (NIH) Rapid Acceleration of Diagnostics (RADx) Tech program and allows consumers to anonymously report their test results from OTC at-home COVID-19 test.

Step-by-Step Guide:
When to Test and What Your At-Home COVID-19 Antigen Test Results Mean

Understanding COVID-19 Infection and the Risk of Spreading the Virus

When you are exposed to the virus that causes COVID-19, it may get into your nose, throat, and lungs (which make up your respiratory tract) and cause an infection. You may never develop symptoms of an infection or you may not have symptoms for several days after you are exposed to the virus, despite being infected. You could still pass the virus to others, even if you do not feel sick.

The amount of virus in an infected person's body may vary in different people, as well as at different times during the infection. There may also be differences in whether, or how easily, the virus can spread to another person throughout the course of the infection. Generally, the amount of virus in a person will start low, increase, then decrease again as a result of the body's immune response. The pattern of this increase and decrease, as well as the level of virus, varies from person to person, and there is no known level above which you can spread the virus and below which you cannot.

The FDA is aware of counterfeit at-home over-the-counter (OTC) COVID-19 diagnostic tests being distributed or used in the United States. These counterfeit tests should not be used or distributed.

Counterfeit COVID-19 tests are tests that are not authorized, cleared, or approved by the FDA for distribution or use in the United States, but are made to look like authorized tests so the users will think they are the real, FDA-authorized test. The performance of these counterfeit tests has not been adequately established and the FDA is concerned about the risk of false results when people use these unauthorized tests.

You may risk unknowingly spreading COVID-19 and may delay or stop appropriate medical treatment for COVID-19 if you use a counterfeit test.

• A false-negative antigen test result means that the test says the person does not have COVID-19 but they actually do have COVID-19. A false-negative result may lead to delayed diagnosis or inappropriate treatment of SARS-CoV-2, which may cause people harm including serious illness and death. False-negative results can also lead to further spread of the SARS-CoV-2 virus, including when people are housed together in health care, long-term care, and other facilities based on these false test results. When false negative test results are received, actions to limit exposure to an infected person might not be taken, such as isolating people, limiting contact with family and friends, or limiting access to places of employment.
• A false-positive antigen test result means that the test says the person has COVID-19 but they actually do not have COVID-19. A false-positive result may lead to a delay in both the correct diagnosis and appropriate treatment for the actual cause of a person’s illness, which could be another life-threatening disease that is not COVID-19. False-positive results could also lead to further spread of the SARS-CoV-2 virus when presumed positive people are housed together.

How do I know if my at-home OTC COVID-19 diagnostic test is FDA-authorized?

The FDA has a list of authorized at-home OTC COVID-19 diagnostic tests. For more information about each test, including the Letter of Authorization and authorized labeling, see In Vitro Diagnostics EUAs: Tables of IVD EUAs.

Check this page regularly to see if the FDA is aware of counterfeit versions of the tests. If the test you have has the same name as one listed on this page, follow the instructions below to check for signs that it is counterfeit or to confirm that it is the real, FDA-authorized product. You can also contact the manufacturer of the test if you have questions or concerns, and they will be able to help you determine if your test is FDA-authorized or counterfeit.

The FDA is not aware of any counterfeit tests distributed by the U.S. Government test distribution programs.

What are some signs that an at-home OTC COVID-19 diagnostic test may be counterfeit?

• Poor print quality of images or text on the outside box label for the product or in the instructions for use included in the box.
• Missing information on the outside box label for the product, such as the lot number, expiration date, or barcode or QR codes.
• Grammatical or spelling errors found in product labeling.
• Components of the kits do not match the content description (for example, missing Instructions for Use, missing or unfilled components, different number of components than listed).
• Tradename for product printed on component or box labels differ from the authorized labeling found on the FDA website: At-Home OTC COVID-19 Diagnostic Tests | FDA.
• The box label or printed instructions for use look different from the authorized labeling found on the FDA website: At-Home OTC COVID-19 Diagnostic Tests | FDA.

What products has the FDA identified as counterfeit at-home OTC COVID-19 diagnostic tests?

Counterfeit Flowflex COVID-19 Test Kits

Do not use counterfeit Flowflex COVID-19 Test Kits.

The FDA is aware that counterfeit versions of the FDA-authorized Flowflex COVID-19 Antigen Home Tests are being illegally imported and distributed in the United States through unauthorized distributors and resellers who have no connection to ACON Laboratories, Inc. These counterfeit tests have not been reviewed or authorized by FDA, but current evidence suggests the counterfeit tests are not performing as well as the authorized tests. The packaging and components of the fraudulent tests very closely resemble real, FDA-authorized Flowflex tests. The FDA-authorized Flowflex tests are still safe to use when following the authorized instructions for use.

The fraudulent tests discussed on this page are not the same as the previously reported issue with the unauthorized ACON Biotech Flowflex SARS-CoV-2 Antigen Rapid Test (Self-Testing). In March 2021, the FDA warned people not to use certain ACON Biotech Flowflex COVID-19 tests packaged in a dark blue box because they have not been cleared or approved by the FDA for distribution or use in the United States.

The FDA is providing the information on this page to help consumers identify counterfeit test kits that imitate the FDA-authorized Flowflex COVID-19 Antigen Home Tests (in white boxes), but are not authorized, cleared, or approved by the FDA for distribution or use in the United States. ACON Laboratories, Inc. has also issued a public notice of this issue.

Below are images and descriptions comparing the counterfeit product to the FDA-authorized test.

• The counterfeit white retail boxes are missing the Lot Number / Expiration Date / 2D-datamatrix label that is found on FDA-authorized Flowflex COVID-19 Antigen Home Tests:

• The counterfeit test kits are missing the Spanish language Instructions For Use. The FDA-authorized Flowflex test kits include both English and Spanish Instructions For Use.

• The counterfeit pouches inside the box that contain the test cassette are labeled as “SARS-COV-2 ANTIGEN RAPID TEST (SELF-TESTING),” whereas the FDA-authorized Flowflex test cassette pouches are labeled “COVID-19 ANTIGEN HOME TEST”:

• The plastic test cassette may have a 2D barcode which differs from the one printed on FDA-authorized Flowflex tests. The counterfeit tests may have a QR code containing square shapes within a square box on 3 corners of the code, as shown below. The FDA-authorized Flowflex tests have a 2D-datamatrix without those three boxes.

Counterfeit iHealth COVID-19 Antigen Rapid Test Kits

Do not use counterfeit iHealth COVID-19 Antigen Rapid Test Kits.

The FDA is aware that counterfeit versions of the FDA-authorized iHealth COVID-19 Antigen Home Tests are being illegally imported and distributed in the United States through unauthorized distributors and resellers who have no connection to iHealth Labs, Inc. These counterfeit tests have not been reviewed or authorized by FDA, and the FDA has no current evidence of their performance. The packaging and components very closely resemble real, FDA-authorized iHealth tests. The FDA-authorized iHealth tests are still safe to use when following the authorized instructions for use.

Below are images and descriptions comparing the counterfeit product to the FDA-authorized test.

• The FDA is aware that there are not many easily identifiable differences between the counterfeit tests and authorized iHealth tests. There may also be different versions of the counterfeit tests. The FDA is continuing to work with iHealth on how to best identify the counterfeit tests. The general signs that an OTC COVID-19 diagnostic test may be counterfeit provided above on this page may apply to some of these counterfeit versions (for example: poor print quality of images or text on the outside box label for the product or in the instructions for use included in the box or grammatical or spelling errors found in product labeling.)
• In some cases, the paper Instructions for Use included in the box with the counterfeit test may have a minor difference in the images showing examples of positive test results. As shown in the red box in the image below, the line is black and extends past the top of the “results window”:

What should I do if I have a counterfeit at-home OTC COVID-19 diagnostic test?

Do not use the counterfeit tests. Contact the distributor or store where you purchased the test to inform them that you received a counterfeit test, and also inform the manufacturer of the authorized test. The manufacturer may ask you for additional information such as photos of the packaging to further investigate the issue. After providing any requested information to the distributor and/or manufacturer, follow the manufacturer’s instructions for returning or disposing of the test.

Talk to your health care provider if you think you were tested with a counterfeit test and you have concerns about your test results.

What is the FDA doing about counterfeit at-home OTC COVID-19 diagnostic tests?

The distribution of counterfeit COVID-19 products is a threat to the public health. The FDA regularly monitors the marketing of unauthorized, unapproved, or uncleared tests, including reports of problems with test performance or results. The FDA is working with manufacturers to address this safety issue.

The FDA will continue to keep the public informed of significant new information.

How do I report a problem with an at-home OTC COVID-19 diagnostic test?

If you think you had a problem with a COVID-19 test, the FDA encourages you to report the problem through the MedWatch Voluntary Reporting Form.

Health care personnel employed by facilities that are subject to the FDA's user facility reporting requirements should follow the reporting procedures established by their facilities.

When you get tested:

• Make sure to test at the right time
• Choose the right type of test for your circumstance
• Follow test directions as recommended by FDA

If you do not, your results may be less likely to correctly indicate whether you have COVID-19 or not.

Types of Tests

Viral tests look for a current infection with SARS-CoV-2, the virus that causes COVID-19, by testing specimens from your nose or mouth. All tests should be performed following FDA’s requirements.

There are two main types of viral tests:

• Polymerase Chain Reaction (PCR) tests
• Antigen tests

PCR Tests

PCR tests are the “gold standard” for COVID-19 tests. They are a type of nucleic acid amplification test (NAAT), which are more likely to detect the virus than antigen tests. Your sample will usually be taken by a healthcare provider and transported to a laboratory for testing. It may take up to 3 days to receive results.

Antigen Tests

Antigen tests* are rapid tests that usually produce results in 15-30 minutes. Positive results are very accurate and reliable. However, in general, antigen tests are less likely to detect the virus than PCR tests, especially when symptoms are not present. Therefore, a single negative antigen test cannot rule out infection. To be confident you do not have COVID-19, FDA recommends 2 negative antigen tests for individuals with symptoms or 3 antigen tests for those without symptoms, performed 48 hours apart. A single PCR test can be used to confirm an antigen test result.

*Self-tests, or at-home tests, are antigen tests that can be taken anywhere without having to go to a specific testing site. Read self-test package inserts thoroughly and follow the instructions closely when performing the test.

When to Get Tested for COVID-19

Key times to get tested:

If you have symptoms, test immediately.

• If you are only going to take a single test, a PCR test will provide a more reliable negative test result.
• If you use an antigen test, a positive result is reliable, but a negative test is not always accurate.
• If your antigen test is negative, take another antigen test after 48 hours or take a PCR test as soon as you can.

If you do not have symptoms but have been exposed to COVID-19, wait at least 5 full days after your exposure before taking a test.

• If you are only going to take a single test, a PCR test will provide a more reliable negative test result.
• If you use an antigen test, a positive result is reliable, but a negative test is not always accurate.
• If your antigen test is negative, take another antigen test after 48 hours or take a PCR test as soon as you can.
• If your second antigen test is also negative, wait another 48 hours and test a third time.

Testing can be helpful even when you don’t have symptoms or a recent exposure to COVID-19, such as before an event or visiting someone at higher risk. Test as close to the time of the event as possible (at least within 1-2 days) to help you make informed decisions about your health and your risk of spreading COVID-19 to others. If you use an antigen test, follow recommendations for repeat testing to be confident in a negative result. Additionally, some places may test people without symptoms or a recent exposure to help keep COVID-19 from spreading to others, especially those who are at higher risk for severe illness.

Choosing a COVID-19 Test

I am in a circumstance where I should get tested and:

I have not had COVID-19 or I have not had a positive test within the past 90 days.

You may choose a PCR or antigen test.
If you use an antigen test and your result is negative, repeat testing following FDA recommendations.

I tested positive for COVID-19 in the last 90 days.

My first positive test result was within:

30 days or less

I have symptoms
Use an antigen test. Repeat negative tests following FDA recommendations.

I do not have symptoms
Testing is not recommended to detect a new infection.

My first positive test result was within:

31-90 days

I have symptoms
Use an antigen test. Repeat negative tests following FDA recommendations.

I do not have symptoms
Use an antigen test. Repeat negative tests following FDA recommendations.

After a positive test result, you may continue to test positive for some time. Some tests, especially PCR tests, may continue to show a positive result for up to 90 days. Reinfections can occur within 90 days, which can make it hard to know if a positive test indicates a new infection. Consider consulting a healthcare provider if you have any questions or concerns about your circumstances.

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Getting a COVID-19 Test

Order Free At-Home Tests

Four (4) free at-home COVID-19 tests are available for U.S. households through the federal government at Covid.gov/tests.

Buy self-tests (at-home tests)

Buy self-tests (at-home tests) online or in pharmacies and retail stores. Private health insurance may reimburse the cost of purchasing self-tests. Visit FDA’s website for a list of authorized tests. Self-tests are antigen tests.

Go to a testing location

• Visit a community-based testing location, such as a pharmacy or health center near you. These locations may offer PCR or antigen tests, and provide low- or no-cost testing for everyone, including people without insurance. Free PCR or antigen tests may also be available through your local health department.
• Talk to a doctor or healthcare provider about other testing options that may be available to you.
• If you are a person with a disability, the Disability Information and Access Line can help you access a test or find a test location.

Interpreting Your Results

If Your COVID-19 Test Is Positive

Any positive COVID-19 test means the virus was detected and you have or recently had an infection.

• Isolate and take precautions, including wearing a high-quality mask or respirator, to protect others around you from getting infected.
• Tell people you had recent contact with that they may have been exposed.
• Monitor your symptoms. If you have any emergency warning signs, seek emergency care immediately.
• Contact a healthcare provider, community health center, or pharmacy to learn about treatment options that may be available to you. Treatment must be started within the first few days to be effective.
  • You are more likely to get very sick if you are an older adult or have an underlying medical condition. Treatment is available. Talk with your healthcare provider to determine what is the best option for you.

If Your COVID-19 Test Is Negative

A negative COVID-19 test means the test did not detect the virus, but this doesn’t rule out that you could have an infection. If you used an antigen test, follow FDA recommendations for repeat testing.

• If you have symptoms:
  • You may have COVID-19 but tested before the virus was detectable.
  • Consider that you may have another viral infection or illness that you need to get tested for. For many diseases, including flu, early diagnosis and prompt treatment is very important for preventing severe illness.
  • Take everyday preventive actions to prevent spreading an illness to others.
  • Contact a healthcare provider if you have any questions about your test result or if your symptoms worsen.
• If you do not have symptoms but were exposed to the virus that causes COVID-19, you should continue to take recommended steps after exposure.
• If you do not have symptoms and have not been exposed to the virus that causes COVID-19, you may return to normal activities.
  • Continue to take steps to protect yourself and others, including monitoring for symptoms. Get tested again if symptoms appear.

Testing for Antibodies

Antibody tests detect antibodies that your body makes to fight the virus that causes COVID-19. Antibody tests should never be used to diagnose a current infection with the virus that causes COVID-19. An antibody test may not show if you have a current infection, because it can take 1 to 3 weeks after the infection for your body to make antibodies. Antibody tests can be used for public health surveillance or to test for conditions associated with COVID-19.