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CoQ10 side effects and how to avoid them

CoQ10 side effects include upset stomach, abdominal pain, and nausea, but they’re very rare
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By | Dec. 29, 2023 Medically reviewed by Josephine Bawab, Pharm.D.
Six gel capsules: Coq10 side effects and how to avoid them

Key takeaways

  • CoQ10 can cause rare side effects such as upset stomach and abdominal pain, but serious side effects are not known, and it’s generally considered safe.

  • It is beneficial for people with conditions that reduce CoQ10 levels, improving heart function, reducing high blood pressure, and supporting individuals with neurodegenerative disorders.

  • CoQ10 may interact with certain medications like warfarin and beta-blockers, and it’s advised to consult healthcare professionals before starting a supplement regime.

  • To avoid side effects, it’s recommended to start with a low dose, consult a healthcare professional, and take CoQ10 with food.

In this article:

Coenzyme Q10 (or CoQ10, CoQ, or vitamin Q10) is a vitamin-like molecule that is essential to cells’ ability to generate energy. It also has powerful antioxidant properties. The body naturally makes CoQ10, but we also get it in our diet by eating meat, fish, and organ meats, such as liver. Still, people often take CoQ10 as a dietary supplement (e.g., ubiquinone or ubiquinol) because it may increase energy levels, improve physical performance, bolster heart health, and reduce oxidative stress. Coenzyme Q10 is also recommended for people with certain conditions, such as diabetes, cancer, muscle diseases, nerve degeneration diseases, high cholesterol, heart disease, and congestive heart failure, that reduce coenzyme Q10 levels in the blood. Some people take it to improve muscle pain and muscle damage (myopathy) due to statins. 

According to some research, CoQ10 may improve heart function in people with heart failure, lower blood pressure, reduce high cholesterol in people with diabetes, prevent migraine headaches, decrease pain and fatigue due to fibromyalgia, and improve the symptoms of Parkinson’s disease or certain types or neurodegenerative disorders. However, the evidence is limited. Still, some healthcare professionals advise or prescribe CoQ10 as a complementary therapy for these conditions.

Common side effects of CoQ10

The most common side effect of CoQ10 is digestive system discomfort (e.g., stomach upset, abdominal pain, and nausea), but this side effect is comparatively rare.

Other side effects of CoQ10 are infrequently experienced and include:

  • Heartburn
  • Loss of appetite
  • Insomnia (when taking 100 mg or more per day)
  • Increase in liver enzymes (when taking 300 mg or more per day)

Other rare side effects include: 

  • Fatigue
  • Irritability
  • Headache
  • Light sensitivity
  • Involuntary movements
  • Dizziness
  • Itching
  • Skin rash

Serious side effects of CoQ10

CoQ10 has no known serious side effects.

CoQ10 and liver health

CoQ10 does not damage the liver, though one older study detected elevated liver enzymes in people taking 300 mg per day over a long period of time. Although elevated liver enzymes are a sign of liver dysfunction, there is no evidence that CoQ10 hurts the liver. In fact, not only is CoQ10 naturally present in the liver, but the liver has the highest concentration of coenzyme Q10 in the body, along with the heart, kidneys, and pancreas. 

Research and experience suggest that CoQ10 may improve liver function because of its antioxidant properties. One study of CoQ10 supplementation in people with non-alcoholic fatty liver disease, published in the journal Food Science & Nutrition, found that CoQ10 supplements reduced liver enzyme levels in the bloodstream. 

How soon do CoQ10 side effects start?

CoQ10 side effects are comparatively mild and usually involve gastrointestinal complaints. These usually start early. There may be other factors, such as diet, medical conditions, or product impurities, that may contribute to these digestive system problems. Rare side effects, such as insomnia, may be more likely at high doses. Elevated liver enzymes are a delayed side effect and have only been reported in people taking high doses over an extended amount of time.

How long do CoQ10 side effects last?

Adverse effects of CoQ10 supplementation are uncommon and mainly involve the digestive system. One study of over 2,600 patients taking CoQ10 supplements found only 36 people who reported side effects, an incidence of around 1%. The most common side effects reported were abdominal pain and nausea. The body may adapt to the drug over time, so these side effects may become more bearable or go away completely. 

What are the long-term side effects of CoQ10?

Only one study has shown that long-term use of CoQ10 can cause elevated liver enzymes, but this has been contradicted by other studies, such as the one published in Food Science & Nutrition, that show that CoQ10 can reduce elevated liver enzymes. Otherwise, there are no known side effects due to long-term use of CoQ10. 

CoQ10 interactions

CoQ10 has no reported drug interactions, but there are a few drugs that it could theoretically interact with:

  • Warfarin: Warfarin is a blood thinner that blocks vitamin K, the molecule that initiates the blood clotting process. People taking warfarin should not increase their intake of vitamin K because that interferes with the ability of warfarin to prevent blood clots. CoQ10 is chemically very similar to vitamin K, so CoQ10 supplementation could reduce the effectiveness of warfarin. One placebo-controlled clinical trial with 24 patients found that low-dose CoQ10 did not interfere with warfarin treatment. Still, people taking warfarin should avoid CoQ10 supplementation to be safe.
  • Beta-blockers: Beta-blockers may inhibit some of the beneficial effects of CoQ10 supplements.
  • Insulin: CoQ10 can reduce blood sugar, so people on insulin may need their doses reduced.

Safety measures while using CoQ10

What are the FDA warnings about CoQ10?

The Food and Drug Administration (FDA) has not issued any warnings about CoQ10. It is available over the counter, so the FDA has determined that it’s safe to use without medical supervision. Keep in mind that the FDA does not regulate supplements as closely as prescription drugs, so there may be doubts about what additives are in the supplement, the supplement’s quality, and its possible impurities. The FDA periodically recalls dietary supplements because of impurities, manufacturing problems, the presence of prescription drugs in the product, and unsubstantiated health claims.

Who should never take CoQ10?

Nobody is prohibited from taking coenzyme Q10 supplements, but women who are pregnant or breastfeeding should avoid CoQ10.

Who should use caution with CoQ10?

The FDA supplement information sheet advises anyone with a medical condition to seek medical advice from a healthcare professional before taking CoQ10 supplements. Although considered to be a safe dietary supplement, CoQ10 should be used with caution or avoided entirely by:

  • Pregnant or breastfeeding women: There is no evidence that CoQ10 affects a pregnancy, a fetus, or a nursing baby. However, there are no studies that show that it is safe either. Women who are pregnant or breastfeeding are cautioned to avoid CoQ10 supplementation.
  • People with cancer: There is little information about the interactions between CoQ10 and cancer chemotherapy, so healthcare professionals may advise against its use during cancer treatment.
  • People with breast cancer: One study showed that patients with breast cancer who take CoQ10 supplements or any other types of antioxidants, such as vitamin A, vitamin C, vitamin E, or carotenoids, before or during treatment are more likely to experience a recurrence.
  • People with kidney disease or liver disease: Although some doctors may advise CoQ10 supplementation for nonalcoholic fatty liver disease, there is little information about its effects on people with those problems, so talk to a doctor before taking CoQ10 supplements.

Does CoQ10 cause drug abuse or dependency?

No. There is little or no risk of abusing CoQ10 supplements or developing a physical dependency.

Can you overdose on CoQ10?

There have been no reports of CoQ10 overdose symptoms, even though some people have been given high doses of 1,200 mg per day. However, if too much CoQ10 is ingested, call Poison Control at 800-222-1222.

Is CoQ10 safe for children?

As a dietary supplement, CoQ10 is only recommended for adults ages 18 years and older. Keep this supplement out of the reach of children. However, CoQ10 may be prescribed to children as young as newborns for congenitally low levels of CoQ10 or mitochondrial disorders. The mitochondria are the power generators inside cells, and CoQ10 helps synthesize the fuel that produces cellular energy.

Is CoQ10 safe for seniors?

There are no warnings against seniors taking CoQ10. However, any older adult with a chronic medical condition should get medical advice from their primary care provider or other healthcare provider before starting CoQ10 supplements.

How to avoid CoQ10 side effects

1. Get medical advice from a healthcare professional first.

Before taking coenzyme Q supplements, talk to a doctor or healthcare provider first. Tell them about all health conditions that you have and the prescription medications, over-the-counter (OTC) drugs, and dietary supplements that you take. 

2. Take the suggested dose.

CoQ10 comes in dosage strengths of 30 mg to 600 mg. Use the suggested dose on the packaging, but it may be advisable to start with the lowest possible dose.

3. Do not overdo it.

Taking large doses of CoQ10 (over 100 mg per day) may not be worth it unless the dosage is prescribed by a doctor. Larger doses make side effects, such as insomnia, more likely.

4. Don’t keep taking CoQ10 if it doesn’t work.

If CoQ10 does not help increase energy levels, improve physical performance, or provide other benefits, such as reducing high blood pressure, there’s no reason to spend the money and risk the side effects. Take CoQ10 if you have a reason to do so and can determine if the supplement is helping.

5. Take CoQ10 with food.

The most common problems people have with CoQ10 supplements are digestive system issues, such as stomach pain, stomach upset, and nausea. Taking the supplement with food may help prevent or minimize these problems.

How to treat side effects of CoQ10

CoQ10 side effects are minimal and not commonly experienced.

Digestive system issues are the most commonly experienced side effects of CoQ10. If CoQ10 is causing stomach upset, abdominal pain, nausea, or diarrhea, try taking the supplement with food. If that doesn’t work, try switching to a different CoQ10 product.

If CoQ10 is causing headaches, use OTC pain relievers, like ibuprofen or acetaminophen.

If you’re having problems falling asleep, reduce the CoQ10 dose.

Bottom line: Is CoQ10 safe?

CoQ10 is considered to be a safe supplement with numerous health benefits, particularly for people with medical conditions that reduce the body’s natural levels of CoQ10, such as heart failure, cardiovascular disease, or neurodegenerative disorders. Side effects are minimal and experienced in less than 1% of people taking the supplement, according to the drug label. There are no known severe adverse effects. Drug interactions are also minimal. 

However, there are some precautions that people should take. If you have a medical condition, talk to a doctor or other healthcare professional about taking CoQ10 before you start. Women who are pregnant or breastfeeding are urged to avoid CoQ10. Unless prescribed by a doctor, don’t give CoQ10 to children or teens younger than the age of 18 years.