Coenzyme Q10 (CoQ10) is a substance that is naturally present in the human body, with the highest levels in the heart, liver, kidneys, and pancreas. It is sold in the United States as a dietary supplement. Because CoQ10 has important functions in the body and because people with some diseases have reduced levels of this substance, researchers have been interested in finding out whether CoQ10 supplements might have health benefits.

Bottom Line

• CoQ10 has not been shown to be of value in treating cancer, but it may reduce the risk of heart damage caused by one type of cancer chemotherapy drug.
• Only a few studies have looked at whether CoQ10 might help prevent heart disease, and their results are inconclusive. Research on the effects of CoQ10 in heart failure is also inconclusive. However, there is evidence that CoQ10 may reduce the risk of some complications of heart surgery.
• Although results of individual studies have varied, the overall scientific evidence does not support the idea that CoQ10 can reduce muscle pain caused by the cholesterol-lowering drugs known as statins.
• The small amount of evidence currently available suggests that CoQ10 probably doesn’t have a meaningful effect on blood pressure.
• A major National Institutes of Health-funded study showed that CoQ10, even in higher-than-usual doses, didn’t improve symptoms in patients with early Parkinson’s disease. A 2017 evaluation of this study and several other, smaller studies concluded that CoQ10 is not helpful for Parkinson’s symptoms.
• CoQ10 has also been studied for a variety of other conditions, including amyotrophic lateral sclerosis (Lou Gehrig’s disease), Down syndrome, Huntington’s disease, and male infertility, but the research is too limited for any conclusions to be drawn.

Safety

• No serious side effects of CoQ10 have been reported. Mild side effects such as insomnia or digestive upsets may occur.
• CoQ10 may interact with the anticoagulant (blood thinner) warfarin and the diabetes drug insulin, and it may not be compatible with some types of cancer treatment.

There is some limited evidence that coenzyme Q10 may help reduce the duration and frequency of migraines but not their severity.

What Does the Research Show?

• A 2021 systematic review and meta-analysis of 6 studies (371 total participants), which compared coenzyme Q10 with a placebo, showed that coenzyme Q10 may help reduce the duration and frequency of migraines but not their severity. Because both the amount of evidence and the size of the effects observed in the studies were small, there are still uncertainties about whether coenzyme Q10 is helpful for migraines.

Safety

• No serious side effects of coenzyme Q10 have been reported. Coenzyme Q10 may interact with some medications, including the anticoagulant (blood-thinning) medication warfarin and the diabetes drug insulin.

Overview

• Coenzyme Q10 (known as CoQ10) is a compound that is made in the body. The body uses it for cell growth and to protect cells from damage (see Question 1).
• Clinical trials have been limited to small sizes. It is not clear if the benefits reported were from the CoQ10 therapy (see Question 4).
• CoQ10 may not mix safely with other drugs. It is important that patients tell their health care providers about all drugs they are taking (see Question 5).
• CoQ10 is sold as a dietary supplement rather than a drug and is not regulated by the US Food and Drug Administration (see Question 6).

Questions and Answers About Coenzyme Q10 (CoQ10)

1. What is CoQ10?

   CoQ10 is a compound that is made in the body. The Q and the 10 in coenzyme Q10 refer to the groups of chemicals that make up the product. CoQ10 is also known by the following names:

   • Q₁₀.
   • Vitamin Q₁₀.
   • Ubiquinone.
   • Ubidecarenone.

   A coenzyme helps an enzyme do its job. An enzyme is a protein that speeds up the rate at which chemical reactions take place in cells of the body. The body's cells use CoQ10 to make energy needed for the cells to grow and stay healthy. The body also uses CoQ10 as an antioxidant. An antioxidant protects cells from chemicals called free radicals.

   CoQ10 is found in most body tissues. The highest amounts are found in the heart, liver, kidneys, and pancreas. The lowest amounts are found in the lungs. CoQ10 decreases in the body as people get older.

2. How is CoQ10 given?

   CoQ10 is taken by mouth as a tablet or capsule. It may also be given by injection into a vein (IV).

3. Have any laboratory or animal studies been done using CoQ10?

   In laboratory studies, tumor cells are used to test a substance to find out if it is likely to have any anticancer effects. In animal studies, tests are done to see if a drug, procedure, or treatment is safe and effective in animals. Laboratory and animal studies are done before a substance is tested in people.

   Laboratory and animal studies have tested the effects of coenzyme Q10.

4. Have any studies of CoQ10 been done in people?

   There have been few clinical trials that study the use of CoQ10 in patients with cancer.

   A trial of 236 breast cancer patients were randomized to receive either CoQ10 or placebo, each combined with vitamin E, for 24 weeks. The study found that levels of fatigue and quality of life were not improved in patients who received CoQ10 compared to patients who received the placebo.

   A randomized trial of 20 children treated for acute lymphoblastic leukemia or non-Hodgkin lymphoma looked at whether CoQ10 would protect the from the damage caused by doxorubicin. The results reported that CoQ10 decreased the harmful effects of doxorubicin on the heart.

   Clinical trials have been limited to small numbers of people, and it is not clear if the benefits reported were from the CoQ10 therapy, other dietary supplements, or standard treatments used before or during the CoQ10 therapy.

5. Have any side effects or risks been reported from CoQ10?

   Reported side effects from the use of CoQ10 include the following:

   • High levels of liver enzymes.
   • Nausea.
   • Heartburn.
   • Headache.
   • Pain in the upper part of the abdomen.
   • Dizziness.
   • Rashes.
   • Unable to fall sleep or stay asleep.
   • Feeling very tired.
   • Feeling irritable.
   • Sensitive to light.

   Importantly, clinical trials that studied the use of CoQ10 to prevent toxic side effects during cancer treatments (for example, chemotherapy and radiation therapy) have not followed patients over the long term to find whether CoQ10 made the treatments less effective.

   A recent observational study in patients with breast cancer suggested that the use of antioxidant supplements, including CoQ10, before and during cancer treatment may be linked with increased recurrence rates and decreased survival.

   It is important to check with health care providers to find out if CoQ10 can be safely used with other drugs. Certain drugs, such as those that are used to lower cholesterol, blood pressure, or blood sugar levels, may decrease the effects of CoQ10. CoQ10 may change the way the body uses warfarin (a drug that prevents the blood from clotting) and insulin.

6. Is CoQ10 approved by the US Food and Drug Administration (FDA) for use as a cancer treatment in the United States?

   The U.S. Food and Drug Administration (FDA) has not approved the use of CoQ10 as a treatment for cancer.

   The FDA does not approve dietary supplements as safe or effective. The company that makes the dietary supplements is responsible for making sure that they are safe and that the claims on the label are true and do not mislead the patient. The way that supplements are made is not regulated by the FDA, so all batches and brands of CoQ10 supplements may not be the same.

Only a few trials have been conducted on coenzyme Q10 for Parkinson’s disease, so there aren’t enough data to determine whether coenzyme Q10 has any effect on symptoms.

What Does the Research Show?

• The American Academy of Neurology’s practice parameter on neuroprotective strategies and alternative therapies for Parkinson’s disease concluded that there is insufficient evidence to support or refute the use of coenzyme Q10 for neuroprotection.
• A 2014 randomized clinical trial of 600 participants with Parkinson’s disease concluded that coenzyme Q10 was safe and well tolerated in this population, but showed no evidence of clinical benefit.
• A 2002 randomized controlled trial of 80 participants with early Parkinson’s disease found that less disability developed in subjects assigned to coenzyme Q10 than in those assigned to placebo; however, the results did not reach statistical significance.

Safety

• Studies have not reported serious side effects related to CoQ10 use. The most common side effects of CoQ10 include insomnia, increased liver enzymes, rashes, nausea, upper abdominal pain, dizziness, sensitivity to light, irritability, headaches, heartburn, and fatigue.
• CoQ10 may make warfarin less effective.

Primary coenzyme Q10 deficiency is a disorder that can affect many parts of the body, especially the brain, muscles, and kidneys. As its name suggests, the disorder involves a shortage (deficiency) of a substance called coenzyme Q10.

The severity, combination of signs and symptoms, and age of onset of primary coenzyme Q10 deficiency vary widely. In the most severe cases, the condition becomes apparent in infancy and causes severe brain dysfunction combined with muscle weakness (encephalomyopathy) and the failure of other body systems. These problems can be life-threatening. The mildest cases of primary coenzyme Q10 deficiency can begin as late as a person's sixties and often cause cerebellar ataxia, which refers to problems with coordination and balance due to defects in the part of the brain that is involved in coordinating movement (cerebellum). Other neurological abnormalities that can occur in primary coenzyme Q10 deficiency include seizures, intellectual disability, poor muscle tone (hypotonia), involuntary muscle contractions (dystonia), progressive muscle stiffness (spasticity), abnormal eye movements (nystagmus), vision loss caused by degeneration (atrophy) of the optic nerves or breakdown of the light-sensing tissue at the back of the eyes (retinopathy), and sensorineural hearing loss (which is caused by abnormalities in the inner ear). The neurological problems gradually get worse unless treated with coenzyme Q10 supplementation.

A type of kidney dysfunction called nephrotic syndrome is another common feature of primary coenzyme Q10 deficiency. It can occur with or without neurological abnormalities. Nephrotic syndrome occurs when damage to the kidneys impairs their function, which allows protein from the blood to pass into the urine (proteinuria). Other signs and symptoms of nephrotic syndrome include increased cholesterol in the blood (hypercholesterolemia), an abnormal buildup of fluid in the abdominal cavity (ascites), and swelling (edema). Affected individuals may also have blood in the urine (hematuria), which can lead to a reduced number of red blood cells in the body (anemia), abnormal blood clotting, or reduced amounts of certain white blood cells. Low white blood cell counts can lead to a weakened immune system and frequent infections in people with nephrotic syndrome. If not treated with coenzyme Q10 supplementation, affected individuals eventually develop irreversible kidney failure (end-stage renal disease).

A type of heart disease that enlarges and weakens the heart muscle (hypertrophic cardiomyopathy) can also occur in primary coenzyme Q10 deficiency.