Your family history includes health information about you and your close relatives. Families have many factors in common, including their genes, environment, and lifestyle. Looking at these factors can help you figure out whether you have a higher risk for certain health problems, such as heart disease, stroke, and cancer.

Having a family member with a disease raises your risk, but it does not mean that you will definitely get it. Knowing that you are at risk gives you a chance to reduce that risk by following a healthier lifestyle and getting tested as needed.

You can get started by talking to your relatives about their health. Draw a family tree and add the health information. Having copies of medical records and death certificates is also helpful.

What is family health history?

Family health history is a record of the diseases and health conditions in your family. You and your family members share genes. You may also have behaviors in common, such as exercise habits and what you like to eat. You may live in the same area and come into contact with similar things in the environment. Family history includes all of these factors, any of which can affect your health.

How can I collect my family health history?

You may know a lot about your family health history or only a little. To get the complete picture, use family gatherings as a time to talk about health history. If possible, look at death certificates and family medical records. Collect information about your parents, sisters, brothers, half-sisters, half-brothers, children, grandparents, aunts, uncles, nieces, and nephews. Include information on major medical conditions, causes of death, age at disease diagnosis, age at death, and ethnic background. Be sure to update the information regularly and share what you’ve learned with your family and with your doctor.

Why is family health history important for my health?

Most people have a family health history of at least one chronic disease, such as cancer, heart disease, and diabetes. If you have a close family member with a chronic disease, you may be more likely to develop that disease yourself, especially if more than one close relative has (or had) the disease or a family member got the disease at a younger age than usual.

Collect your family health history information before visiting the doctor, and take it with you. Even if you don’t know all of your family health history information, share what you do know. Family health history information, even if incomplete, can help your doctor decide which screening tests you need and when those tests should start.

How can I use my family health history to improve my health?

You can’t change your genes, but you can change unhealthy behaviors, such as smoking, not exercising or being active, and poor eating habits. If you have a family health history of disease, you may have the most to gain from lifestyle changes and screening tests. In many cases, adopting a healthier lifestyle can reduce your risk for diseases that run in your family. Screening tests, such as diabetes screening, mammograms, and colorectal cancer screening, help find early signs of disease. Finding disease early can often mean better health in the long run.

A family health history is a record of health information about a person and his or her close relatives. A complete record includes information from three generations of relatives, including children, brothers and sisters, parents, aunts and uncles, nieces and nephews, grandparents, and cousins.

Families have similar genetic backgrounds, and often similar environments and lifestyles. Together, these factors can give clues to conditions that may run in a family. By noticing patterns of disorders among relatives, healthcare professionals can determine whether an individual, family members, or future generations may be at an increased risk of developing a particular condition.

A family health history can identify people with a higher-than-usual chance of having common disorders, such as heart disease, high blood pressure, stroke, certain cancers, and type 2 diabetes. These complex disorders are influenced by a combination of genetic factors, environmental conditions, and lifestyle choices. A family history also can provide information about the risk of rarer conditions caused by variants (mutations) in a single gene, such as cystic fibrosis and sickle cell disease.

While a family health history provides information about the risk of specific health concerns, having relatives with a condition does not mean that an individual will definitely develop that condition. On the other hand, a person with no family history of a disorder may still be at risk of developing the disorder.

Knowing one’s family health history allows a person to take steps to reduce his or her risk. For people at an increased risk of certain cancers, healthcare professionals may recommend more frequent screening (such as mammography or colonoscopy) starting at an earlier age. Healthcare providers may also encourage regular checkups or testing for people with a condition that runs in their family. Additionally, lifestyle changes such as adopting a healthier diet, getting regular exercise, and quitting smoking help many people lower their chances of developing heart disease and other common illnesses.

The easiest way to get information about family health history is to talk to relatives about their health. Have they had any health problems, and when did they occur? A family gathering could be a good time to discuss these issues. Additionally, obtaining medical records and other documents (such as obituaries and death certificates) can help complete a family health history. It is important to keep this information up-to-date and to share it with a healthcare professional regularly.

It's the time of year when many families gather for the holidays, which means it's also a great time to learn about your family health history.

Discussing medical conditions or diseases among family members may help determine if you have a high risk for a disease.

That’s because our genes, which we inherit from our birth mother and father, are important in determining our health. For example, sickle cell disease—a blood disorder—is caused by gene mutations that come from a parent.

But just because your parents or other family members have a condition doesn’t mean you have it now or will in the future. That’s why learning about your health history and risk and sharing that information with a doctor is important.

A family medical history can:

• Reveal early warning signs of a condition or disease
• Provide health care providers with information so they can recommend treatment, and assess and possibly reduce risk
• Help improve family members' lifestyles to reduce risk
• Inform a woman of certain genes she has before pregnancy

How to collect a family medical history

There are different ways to collect family health information. You can choose one family member to collect all the health information from various relatives or have each relative fill out their own health record. You can also create a checklist that is organized by medical condition.

If a family member does not want to discuss their health issues around other people, ask to pull them aside and have a private conversation. Try to remind them of the importance of having a family health history.

But remember that health can often be an emotionally charged topic. Listen carefully and try to be as respectful and patient as possible.

For adopted children or children of sperm or egg donations, health records may be available from the original adoption or donation agencies. Genetic testing can also help determine certain conditions.

So, what are good health questions to ask your family? Here are a few you can start with:

1. What is your ethnic background?
2. Where do you live?
3. Where were you born?
4. How old were you or your relative when they developed the medical condition(s)?
5. How many people in your family have had the same conditions or diseases?
6. Have you or any of your family members been tested for genetic mutations (cell changes)?
7. How old were your deceased relatives when they died, and how did they die?
8. What diseases or medical conditions have you had?

Thinking about having a baby? If you have a family health history that includes a birth defect, developmental disability, newborn screening disorder, or genetic disease, you might be more likely to have a baby with this condition. Learning more about your family health history before you get pregnant can give you time to address any concerns. Remember to consider the family health history of both potential parents, not just mom. Be sure to discuss any concerns with your doctor.

Based on your family health history, your doctor might refer you for genetic counseling. Other reasons for genetic counseling include having had

• Infertility (trouble getting pregnant),
• 2 or more miscarriages,
• A previous pregnancy or child with a genetic disease or birth defect, or
• A baby who died at less than 1 year of age.

After genetic counseling, you might decide to have genetic testing for conditions that could affect your baby. Results from these tests could impact your pregnancy planning. Testing before you get pregnant can give you time to think about what the results mean for you and consider all your options.

Carrier Screening

Parents can have a baby with a genetic disease even though neither parent has it. Babies inherit two copies of each genes, one from each parent. For some genetic diseases, the baby will only have the disease if both copies of the gene related to the disease do not work properly. In cases like these, each parent has one copy of the gene that works properly and one that does not. If the baby inherits both non-working copies of the gene, the baby has the disease. Thus, the parents are “carriers” for the disease, meaning that they don’t have the disease themselves but can have children with it.

If a genetic disease runs in your family, you might be a carrier for that disease. Likewise, you might be a carrier for genetic diseases that are more common in your racial or ethnic group. Examples include sickle cell disease in blacks and Tay-Sachs disease in Ashkenazi Jews and Eastern Europeans. Your doctor might ask if you want to have screening, called carrier screening, to check if you are a carrier for diseases that are more common in your racial or ethnic group. Talk to your doctor if you want to know about carrier screening for genetic diseases that run in your family. In addition, current recommendations 1 state that all women should be offered carrier screening for cystic fibrosis.

If the results show that you are a carrier for a disease, the other potential parent would also need to have carrier screening to know if you could have a baby with the disease.

Family Health History Checklist: Planning a Pregnancy

• Gather family history information before seeing the doctor.
• Use the US Surgeon General’s online tool for collecting family histories, called “My Family Health Portrait.”
• Tell your doctor if you have family members with genetic diseases, chromosomal abnormalities, developmental disabilities, birth defects, newborn screening disorders, or other problems at birth or during infancy or childhood, especially if you have had a previous pregnancy or child affected by one of these conditions.
  • Talk to those family members, if possible, to find out their specific diagnoses.
  • Ask for a copy of their genetic or diagnostic test results, if any, to share with your doctor.
• Alert your doctor if you have had a previous preterm (early) birth, miscarriage, stillbirth, or a child who died from sudden infant death syndrome (SIDS).
• Follow your doctor’s recommendations. For example, if you have had a previous pregnancy or child affected by spina bifida or anencephaly, your doctor might recommend that you take a higher than normal dose of the B vitamin, folic acid, before and during pregnancy.

Expecting a baby? You might be wondering whether your baby will have mommy’s eyes or daddy’s dimples. But your baby will inherit much more than that. Learn about both parents’ family health history to give your baby the best start possible. If either of you have a family health history of a birth defect, developmental disability, newborn screening disorder, or genetic disease, your baby might be more likely to have this condition. Knowing if your baby is more likely to have one of these conditions is important so that you can find and address potential health problems early.

Based on your family health history, your doctor might refer you for genetic counseling. Other reasons for genetic counseling include having had

• Infertility (trouble getting pregnant),
• 2 or more miscarriages,
• A previous pregnancy or child with a genetic disease or birth defect, or
• A baby who died at less than 1 year of age.

After genetic counseling, you might decide to have genetic testing. Results from these tests might help you know if your baby could have health issues.

Carrier Screening

Parents can have a baby with a genetic disease even though neither parent has it. Babies inherit two copies of each genes, one from each parent. For some genetic diseases, the baby will only have the disease if both copies of the gene related to the disease do not work properly. In cases like these, each parent has one copy of the gene that works properly and one that does not. If the baby inherits both non-working copies of the gene, the baby has the disease. Thus, the parents are “carriers” for the disease, meaning that they don’t have the disease themselves but can have children with it.

If a genetic disease runs in your family, you might be a carrier for that disease. Likewise, you might be a carrier for genetic diseases that are more common in your racial or ethnic group. Examples include sickle cell disease in blacks and Tay-Sachs disease in Ashkenazi Jews and Eastern Europeans. Your doctor might ask if you want to have screening, called carrier screening, to check if you are a carrier for diseases that are more common in your racial or ethnic group. Talk to your doctor if you want to know about carrier screening for genetic diseases that run in your family. In addition, current recommendations (1) state that all women should be offered carrier screening for cystic fibrosis.

If the results show that you are a carrier for a disease, the other potential parent would also need to have carrier screening to know if you could have a baby with the disease.

Family Health History Checklist: During Pregnancy

• Gather family history information before seeing the doctor.
• Use the US Surgeon General’s online tool for collecting family histories, called “My Family Health Portrait.”
• Tell your doctor if you have family members with genetic diseases, chromosomal abnormalities, developmental disabilities, birth defects, newborn screening disorders, or other problems at birth or during infancy or childhood, especially if you have had a previous pregnancy or child affected by one of these conditions.
  • Talk to those family members, if possible, to find out their specific diagnoses.
  • Ask for a copy of their genetic or diagnostic test results, if any, to share with your doctor.
• Alert your doctor if you have had a previous preterm (early) birth, miscarriage, stillbirth, or a child who died from sudden infant death syndrome (SIDS).
• Follow your doctor’s recommendations. For example, if you have had a previous pregnancy or child affected by spina bifida or anencephaly, your doctor might recommend that you take a higher than normal dose of the B vitamin, folic acid, during pregnancy.

You might not realize that your mother’s diabetes or your cousin’s sickle cell disease could affect your child, but collecting your family history information can be important for keeping your child healthy.

Family health history can help your child’s doctor make a diagnosis if your child shows signs of a disease. It can also reveal whether your child has an increased risk for a disease. If so, the doctor might suggest screening tests. Many genetic diseases first become obvious in childhood, and knowing about a history of a genetic condition can help find and treat the condition early.

Conditions such as autism spectrum disorder, attention-deficit/hyperactivity disorder (ADHD), dyslexiaexternal icon, anxiety and depression, and certain birth defects can run in families. Your child’s doctor might already check your child for these conditions and other developmental, behavioral, learning, and mental health conditions. However, knowing if you, your other children, or any other family members from either side of the family have one of these conditions might help the doctor find the condition earlier if your child shows signs or symptoms. Finding and acting on these conditions earlier can result in improved outcomes for your child. Sometimes, parents recognize that they have a previously undetected condition, such as ADHD, when their child receives a diagnosis, and can get their own diagnosis and treatment. Understanding your family history may help your entire family.

Most people do not think that chronic diseases such as heart disease and type 2 diabetes affect children, but children with a strong family history of these diseases can show signs in childhood. However, having a family history of a disease does not mean that your child will get that disease. Children with a family history of chronic diseases can benefit from developing good lifestyle habits, such as exercising and eating healthy, right away. These habits can benefit the entire family and might help prevent or delay chronic diseases.

Family Health History Checklist: Your Child

□ Record the names of your child’s close relatives from both sides of the family: parents, siblings, grandparents, aunts, uncles, nieces, and nephews. Include conditions each relative has or had, and at what age the conditions were first diagnosed.

□ Use the US Surgeon General’s online tool for collecting family histories, called “My Family Health Portrait.”

□ Discuss family health history concerns with your child’s doctor. Gather family history information before seeing the doctor. Even if you don’t know all of your child’s family health history information, share what you do know with your doctor. Fill out family history forms carefully. Families that might have another child should share family health history information with the mother’s doctor.

□ Update your child’s family health history regularly and share new information with your child’s doctor. Check with relatives between your child’s visits with a doctor to see if they have any newly diagnosed conditions.

Knowing and acting on your family health history can be an important part of staying healthy. Family health history can help your doctor decide what screening tests and other interventions you need and when. For example, if you have a parent, sibling, or child with breast cancer, your doctor might recommend that you start mammography screening earlier. Your doctor also might refer you for cancer genetic counseling, especially if your relative was diagnosed before age 50.

Take the time to collect your family health history information from your family members. It might not be easy–your family members might not be used to talking about their diseases or might not want to talk. But starting the conversation is important. Remember, you’re asking not just for your own health, but for the health of everyone in your family.

If you have a medical condition, such as cancer, heart disease, or diabetes, be sure to let your family members know about your diagnosis. If you have had genetic testing done, share your results with your family members. If you are one of the older members of your family, you may know more about diseases and health conditions in your family, especially in relatives who are no longer living. Be sure to share this information with your younger relatives so that you may all benefit from knowing this family health history information.

Are you ready to collect your family health history but don’t know where to start? Here’s how!

Family Health History Checklist: Adults

• Talk to your family. Write down the names of blood relatives you need to include in your history. The most important relatives to include in your family health history are your parents, brothers and sisters, and your children. Next, you may want to talk to grandparents, uncles and aunts, nieces and nephews, and half-brothers and half-sisters.
• Ask questions. To find out about your risk for chronic diseases, ask your relatives about which of these diseases they have had and when they were diagnosed. Questions can include
  • Do you have any chronic diseases, such as heart disease or diabetes, or health conditions such as high blood pressure or high cholesterol?
  • Have you had any other serious diseases, such as cancer or stroke?
  • How old were you when each of these diseases and health conditions was diagnosed?
  • What is our family’s ancestry – from what countries did our ancestors come to the United States?
  • For relatives who have died, be sure to ask about cause and age of death.
• Record the information. Write this information down, and be sure to update it from time to time.
• Share family health history information with your doctor and other family members. Your family health history can give you an idea of your risk for chronic diseases like cancer, heart disease and diabetes, but it is not the only factor to consider. If you are concerned about diseases that are common in your family, talk with your doctor at your next visit. A doctor can evaluate all of the factors that may affect your risk of some diseases, including family health history, and can recommend ways to reduce that risk.
• Act on your family health history. Having a family health history of a disease does not mean that you or your family members will definitely get that disease. It is important that you talk with your doctor about steps that you can take to lower your chances of getting the disease. You have already taken the first step by learning about your family health history!

If you have a family health history of a chronic disease like cancer, heart disease, diabetes, or osteoporosis, you are more likely to get that disease yourself. Share your family health history with your doctor, who can help you take steps to prevent disease and catch it early if it develops.

If you are a woman with a family health history of breast cancer or ovarian cancer, you may be more likely to get these cancers yourself. Collecting your family health history of breast, ovarian, and other cancers and sharing this information with your doctor can help you find out if you’re at higher risk. If you have had breast, ovarian, or other cancers, make sure that your family members know about your diagnosis.

Your doctor might consider your family health history in deciding when you should start mammography screening for breast cancer. If you are a woman with a parent, sibling, or child with breast cancer, you are at higher risk for breast cancer. Based on current recommendationsexternal icon, you should consider talking to your doctor about starting mammography screening in your 40s. In some cases, your doctor might recommend that you have genetic counseling, and a genetic counselor might recommend genetic testing based on your family health history. Breast, ovarian, and other cancers are sometimes caused by inherited mutations in BRCA1, BRCA2, and other genes. The genetic counselor can help determine which genetic mutations you should be tested for, based on your personal and family health history of cancer, ancestry, and other factors.

When collecting your family health history:

• Include your parents, sisters, brothers, children, grandparents, aunts, uncles, nieces, and nephews
• List any cancers that each relative had and at what age he or she was diagnosed. For relatives who have died, list age and cause of death.
• Remember that breast and ovarian cancer risk doesn’t just come from your mother’s side of the family—your father’s relatives with breast, ovarian, and other cancers matter, too!
• Update your family health history on a regular basis and let your doctor know about any new cases of breast, ovarian, or other cancer.

If you are concerned about your personal or family health history of breast, ovarian, or other cancer, talk to your doctor. Whether or not you have a family health history of breast or ovarian cancer, you can take steps to help lower your risk of breast cancer and ovarian cancer.

Having a family health history of colorectal cancer makes you more likely to get colorectal (colon) cancer yourself.

Knowing your family health history of colorectal cancer and sharing this information with your doctor can help you take steps to lower your risk. If you have multiple relatives who have been diagnosed with colorectal cancer or relatives who have been diagnosed at a young age (before age 50), your doctor may change your medical management to prevent colorectal cancer or catch it as early as possible. If you have been diagnosed with colorectal cancer, it is important to tell your family members.

Based on current recommendations, most people start colorectal cancer screening at age 50, but if you have a family history your doctor may recommend the following:

• Colonoscopy starting at age 40, or 10 years before the age that the immediate family member was diagnosed with cancer,
• More frequent screening,
• Colonoscopy only instead of other tests, and
• In some cases, genetic counseling.

Precancerous colorectal polyps are abnormal growths in the colon or rectum that can turn into cancer if they are not removed. However, not all polyps turn into cancer. If you have been diagnosed with certain types of colorectal polyps, your doctor may recommend starting colonoscopy screening earlier. Be sure to let your family members know about your history of colorectal polyps.

When collecting your family health history

• Include your parents, sisters, brothers, children, grandparents, aunts, uncles, nieces, and nephews
• Make sure to document both your mother’s side of the family and your father’s side of the family
• Document which relatives have had cancer, the type(s) of cancer they have had, and the ages at which they were diagnosed
• Report any history of polyps that each relative has had
• List the age and cause of death for relatives who have died
• Share your family health history with your doctor
• Update your family health history regularly and alert your doctor to any new diagnosis

If you are concerned about your personal or family health history of colorectal cancer, talk to your doctor.

Over 34 million people have diabetes. People with diabetes have levels of blood sugar that are too high. The different types of diabetes include type 1 diabetes, type 2 diabetes, and gestational diabetes. Diabetes can cause serious health problems, including heart disease, kidney problems, stroke, blindness, and the need for lower leg amputations.

People with prediabetes have levels of blood sugar that are higher than normal, but not high enough for them to be diagnosed with diabetes. People with prediabetes are more likely to get type 2 diabetes. About 88 million people in the United States have prediabetes, but most of them don’t know they have it. If you have prediabetes, you can take steps to reverse it and prevent or delay diabetes—but not if you don’t know that you have it.

If you have a family health history of diabetes, you are more likely to have prediabetes and develop diabetes. You are also more likely to get type 2 diabetes if you have had gestational diabetes, are overweight or obese, or are African American, American Indian, Asian American, Pacific Islander, or Hispanic. Learning about your family health history of diabetes is an important step in finding out if you have prediabetes and knowing if you are more likely to get diabetes. You can use the Surgeon General’s family health history tool, My Family Health Portrait, to collect your family health history of diabetes and find out your risk of getting diabetes. Be sure to let your doctor know about your family health history of diabetes, especially if you have a mother, father, sister, or brother with diabetes. Your doctor might recommend that you have screening for diabetes earlier.

Even if you have a family health history of diabetes, you can prevent or delay type 2 diabetes by eating healthier, being physically active, and maintaining or reaching a healthy weight. This is especially important if you have prediabetes, and taking these steps can reverse prediabetes.

Does your mom, dad, sister, or brother have type 2 diabetes?

If so, you could have prediabetes and are more likely to get type 2 diabetes yourself. But there are important steps you can take to prevent type 2 diabetes and reverse prediabetes if you have it.

• Ask your doctor whether you need earlier screening for diabetes.

If you have a family health history of heart disease, you are more likely to develop heart disease yourself.

Different types of heart disease and related conditions, like high blood pressure and high blood cholesterol, can run in families. Knowing your family health history of heart disease and related conditions is one of the first steps you can take to prevent heart disease and heart attacks in the future.

Tell your doctor if your parents, sisters, brothers, children, grandparents, grandchildren, aunts, uncles, nieces, or nephews have or have had

• Heart disease, including
  • Coronary artery disease or atherosclerosis
  • Heart attack
  • High blood cholesterol
  • Angina (pressure or squeezing pain in the chest)
  • Arrhythmias, such as atrial fibrillation
  • Cardiomyopathy
  • Congenital heart defects
  • Heart failure
  • Other heart-related conditions
• Aortic Aneurysm
• Stroke
• Diabetes
• High blood pressure
• Pacemaker
• Percutaneous Coronary Intervention (PCI) (also called coronary angioplasty) with or without stent
• Heart bypass or other heart surgery

Based on this information, your doctor may suggest steps to prevent or treat heart disease. If you have been diagnosed with heart disease or related conditions, it is important to tell your family members.

Tips on collecting your family health history

• Include your parents, sisters, brothers, children, grandparents, grandchildren, aunts, uncles, nieces, and nephews
• Make sure you include both your mother’s and father’s sides of the family
• Note which relatives have had heart disease, related conditions, or procedures and the age at which they were diagnosed or treated
• List the age and cause of death for relatives who have died
• Share your family health history with your doctor and family members
• Update your family health history regularly and alert your doctor to any new diagnosis, condition, or procedure

If you are concerned about your personal or family health history of heart disease, talk to your doctor. If you need help getting started, you can use the My Family Health Portrait tool to collect and share your family health history information. If you or your family members have very high cholesterol levels or have had heart attacks or heart disease at a young age, you might have a family history of familial hypercholesterolemia.

Family Health History of Familial Hypercholesterolemia Last Reviewed: June 16, 2023

If one of your parents has had a broken bone, especially a broken hip, you may need to be screened earlier for osteoporosis. This is a medical condition where bones become weak and are more likely to break. Share your family health history with your doctor. Your doctor can help you take steps to strengthen weak bones and prevent broken bones.

How can osteoporosis affect my health?

People with osteoporosis are more likely to break bones, most often in the hip, forearm, wrist, and spine. While most broken bones are caused by falls, osteoporosis can weaken bones to the point that a break can occur more easily, for example by coughing or bumping into something. As you get older, you are more likely to have osteoporosis and recovering from a broken bone becomes harder. Broken bones can have lasting effects including pain that does not go away. Osteoporosis can cause the bones in the spine to break and begin to collapse, so that some people with it get shorter and are not able to stand up straight. Broken hips are especially serious—afterward, many people are not able to live on their own and are more likely to die sooner.

How can I find out if I have osteoporosis?

Osteoporosis is more common in women. It affects about 25% (1 in 4) of women aged 65 and over and about 5% (1 in 20) of men aged 65 and over. Many people with osteoporosis do not know they have it until they break a bone. Screening is important to find these people before this happens, so they can take steps to decrease the effects of osteoporosis.

Currently, screening for osteoporosis is recommended for women who are 65 years old or older and for women who are 50 to 64 and have certain risk factors, which include having a parent who has broken a hip. Talk to your doctor if you have concerns about osteoporosis.

Screening for osteoporosis is commonly done using a type of low level x-rays called dual/energy x-ray absorptiometry (DXA). Screening also can show if you have low bone mass, meaning your bones are weaker than normal, and are likely to develop osteoporosis.

How can I improve my bone health if I have osteoporosis?

There are steps you can take to improve your bone health and strengthen weak bones:

• Take medications to strengthen your bones and avoid medications that can make your bones weaker.
• Eat a healthy diet that includes adequate amounts of calcium and vitamin D.
• Perform weight-bearing exercises regularly.
• Do not smoke.
• Limit alcohol use.

Don’t wait until you have a broken bone to take steps to improve your bone health—you can start at any age! You can also take steps to prevent falls, including doing exercises to improve your leg strength and balance, having your eyes checked, and making your home safer.

Have you ever met a set of identical twins? Did you have trouble telling them apart? Twins are similar in ways you can’t see, too. That makes twins a powerful tool for studying health and disease.

Many health conditions run in families. If your parents or siblings have a disease, your chance of having it increases. That’s because you share many genes.

Genes are stretches of DNA that you inherit from your parents. They define features like your risk for getting a disease. But that doesn’t mean you’ll get the disease. Many other factors can influence your risk of disease, like how much physical activity you get, your diet, and whether you drink or smoke.

Identical twins make for a natural experiment. They share many things while growing up: the same DNA, their mother’s womb, the same home environment, and the same parents. But as they get older and start living separate lives, they’re exposed to more unique environments. That lets scientists look at differences between twins’ health and their lifestyles as they age.

“There’s a potential with identical twins who are different in terms of disease to see whether we can find the causes,” explains Dr. Thomas Mack, a twin and chronic disease expert at the University of Southern California. That’s because both twins don’t always get a disease, even though they share the same DNA.

Identical twins arise when a fertilized egg splits into two identical fertilized eggs. Since the two eggs share the same genes, identical twins are always the same sex and have the same physical features.

The other type of twin is called fraternal twins. Fraternal twins come from two separate eggs that happened to be fertilized at the same time by two different sperm. These twins get different mixtures of their parents’ genes, so they look just like normal siblings except that they’re the same age.

Mack is studying twins to understand what puts women at higher risk for breast cancer. It’s not clear why one person gets cancer but another doesn’t. His team is looking at differences between identical twins, fraternal twins, and normal siblings.

“There are several common risk factors for breast cancer which include the age at which you have your first baby, age of first menstruation, age of menopause, and whether or not you’ve been an alcohol drinker,” Mack explains.

His work found that fraternal twins and normal siblings had similar risk patterns. But the known risk factors couldn’t explain why one identical twin got breast cancer and the other did not. Now, his team is looking at what else may be involved.

“We want to know what environmental things make a difference between one twin who gets affected by the disease and the other twin who does not,” Mack explains. His team hopes that studying twins will help uncover new risk factors for breast cancer.

Whether or not you’re a twin, knowing your family’s health history is important for your health. It can help your health care team provide better care for you. Talk to your provider about how to lower your risk for diseases that run in your family.

Use Your Family Health History

• Talk with your family. Write down the names of your close relatives on both sides of your family and the conditions they have or had, and at what age they were first diagnosed. Include causes and ages of any deaths.
• Ask questions. Ask your relatives about any chronic diseases and conditions, like heart disease, diabetes, high blood pressure, high cholesterol, cancer, or stroke.
• Record and update the information whenever you learn something new. My Family Health Portrait, a free web-based tool, can help you keep organized.
• Share family health history information with your doctor. Your health care providers can use it to get a more complete picture of your health and risk for disease. Together, you can work on ways to reduce that risk.

Has your mother or sister had breast cancer? Does your mother, father, sister, or brother have diabetes? Did your mother, father, brother, or sister have colorectal (colon) cancer before age 50? If you answered “yes,” you are more likely to get the same disease as your parent or sibling and should consider earlier screening. Talk to your doctor about when to start screening and what other steps to take to prevent the disease or find it early. Finding disease early can often mean better health in the long run.

Did you know that Thanksgiving is also National Family History Day? Even if you don’t have a parent or sibling with cancer or diabetes, you might be more likely to get a disease if other people in your family have or had the disease. However, having a family health history of a disease doesn’t mean that you will definitely get it. Knowing your family health history risk can help you—if you act on it. Collecting your family health history is an important first step. Whether you know a lot about your family health history or only a little, take time to talk to your family about their health histories at family gatherings this holiday season. It might not be easy. Your family members might not be used to talking about their diseases or might not want to talk. But starting the conversation is important. Remember, you’re asking not just for your own health, but for the health of everyone in your family.

How to Collect Your Family Health History

• Talk to your family. Write down the names of your close relatives from both sides of the family: parents, siblings, grandparents, aunts, uncles, nieces, and nephews. Talk to these family members about what conditions they have or had, and at what age the conditions were first diagnosed. You might think you know about all of the conditions in your parents or siblings, but you might find out more information if you ask.
• Ask questions. To find out about your risk for chronic diseases, ask your relatives about which of these diseases they have had and when they were diagnosed. Questions can include:
  • Do you have any chronic diseases, such as heart disease or diabetes, or health conditions, such as high blood pressure or high cholesterol?
  • Have you had any other serious diseases, such as cancer or stroke? What type of cancer?
  • How old were you when each of these diseases or health conditions was diagnosed? (If your relative doesn’t remember the exact age, knowing the approximate age is still useful.)
  • What is your family’s ancestry? From what countries or regions did your ancestors come to the United States?
  • What were the causes and ages of death for relatives who have died?
• Record the informationand update it whenever you learn new family health history information.
• Share family health history information with your doctor and other family members. If you are concerned about diseases that are common in your family, talk with your doctor at your next visit. Even if you don’t know all of your family health history information, share what you do know. Family health history information, even if incomplete, can help your doctor decide which screening tests you need and when those tests should start.

If you have a medical condition, such as cancer, heart disease, or diabetes, be sure to let your family members know about your diagnosis. If you have had genetic testing done, share your results with your family members. If you are one of the older members of your family, you may know more about diseases and health conditions in your family, especially in relatives who are no longer living. Be sure to share this information with your younger relatives so that you may all benefit from knowing this family health history information.

How to Act on Your Family Health History

Knowing about your family health history of a disease can motivate you to take steps to lower your chances of getting the disease. You can’t change your family health history, but you can change unhealthy behaviors, such as smoking, not exercising or being active, and poor eating habits. Talk with your doctor about steps that you can take, including whether you should consider early screening for the disease. If you have a family health history of disease, you may have the most to gain from lifestyle changes and screening tests.

What you can do if you have a family health history of

• Colorectal cancer: If you have a mother, father, sister, brother, or other close family member who had colorectal cancer before age 50 or have multiple close family members with colorectal cancer, talk to your doctor about whether you should have screening starting at a younger age, being done more frequently, and using colonoscopy only instead of other tests. In some cases, your doctor may recommend that you have genetic counseling, and a genetic counselor may recommend genetic testing based on your family health history.
• Breast or ovarian cancer: If you have a parent, sibling, or child with breast cancer, talk to your doctor about when you should start mammography screening. If your relative was diagnosed with breast cancer before age 50, if you have a close relative with ovarian cancer, or if you have a male relative with breast cancer, your doctor might refer you for cancer genetic counseling to find out if genetic testing is right for you. In some cases, your doctor might recommend taking tamoxifen, raloxifene, or aromatase inhibitors, drugs that can decrease risk of developing breast cancer in some women.
• Heart disease: If you have a family health history of heart disease, you can take steps to lower your chances of getting heart disease. These steps can include eating a healthy diet, being physically active, maintaining a healthy weight, not smoking, limiting your alcohol use, having any screening tests that your doctor recommends, and, in some cases, taking medication.
• Diabetes: If your mother, father, brother, or sister has type 2 diabetes, you could have prediabetes and are more likely to get type 2 diabetes yourself. But there are important steps you can take to prevent type 2 diabetes and reverse prediabetes if you have it. Take this test to find out if you could have prediabetes. Ask your doctor whether you need earlier screening for diabetes. Find out more about the National Diabetes Prevention Program’s lifestyle change program and how to find a program near you. Take the Family Health History Quiz to learn more about family health history and diabetes, and learn how to prevent type 2 diabetes.
• Osteoporosis: This is a medical condition where bones become weak and are more likely to break. A family health history of osteoporosis is one of a number of factors that make you more likely to develop osteoporosis. For example, if you are a white woman whose mother or father fractured a hip, talk to your doctor about screening for osteoporosis earlier (at about age 55, compared with age 65 for most women). You can use the FRAX Risk Assessment tool to learn if you should be screened.
• Hereditary Hemochromatosis: Hereditary hemochromatosis is a disorder in which the body can build up too much iron and can lead to serious liver damage and other problems. If you have a brother or sister with hemochromatosis, you may be more likely to develop the condition yourself. Talk to your doctor about testing for hemochromatosis and whether you should take steps to lower the amount of iron in your body.