CoQ10 Side Effects

by on June 11, 2012


Most CoQ10 side effects are mild, including nausea, skin rashes, and headaches, and are related to dosage. Coenzyme Q10 may also affect other medications so individuals should always discuss their treatment with a professional.

Common CoQ10 Side Effects

In most cases, individuals will not experience any side effects of CoQ10, even with prolonged usage. The most common side effects occur in people who take at least 100 mg of coenzyme Q10 on a daily basis. These include:

  • Nausea
  • Upper abdominal pain
  • Headache
  • Fatigue
  • Insomnia or difficulty sleeping
  • Irritability
  • Heartburn
  • Skin rashes
  • Sensitivity to light

When these side effects do occur, they are typically very mild. If any of the symptoms are severe or do not go away, stop using CoQ10 and talk to your doctor.

Serious CoQ10 Side Effects

There are no serious side effects currently associated with the use of CoQ10, although some individuals are at a higher risk of experiencing adverse reactions from the supplement. People who consume more than 300 mg of coenzyme Q10 each day may have higher levels of liver enzymes, but liver toxicity doesn’t appear to be a concern. Other Coq10 side effects that could become serious include:

  • A decrease in blood sugar; a particular concern for patients with diabetes
  • An allergic reaction with symptoms like hives, swelling, or breathing difficulties
  • Persistent insomnia

Discuss the benefits and possible side effects of CoQ10 with your doctor before starting treatment. Be sure he or she is aware of all other medications you are taking and any existing conditions that may affect your body’s reaction to the supplement.

CoQ10 Toxicity

Many vitamins and dietary supplements can be dangerous when consumed in large quantities. Research and observations have found no concern for toxicity side effects with coenzyme Q10, however; even in patients who consumed up to 3600 mg of the supplement per day. Such high dosages are not recommended though.

The observed safe level (OSL) of CoQ10 is 1200 mg per day and typical dosage is usually no more than 300 mg daily.


Coenzyme Q10 occurs naturally in the body and should have no effect on an unborn child in its normal occurrences. The effect of CoQ10 supplements during pregnancy is not known, however, so it is best to avoid taking this medicine if you are pregnant or planning to become pregnant. CoQ10 may pass through breast milk and could cause harm to an infant. Stop taking CoQ10 if you plan to breastfeed.

Other Medications

While CoQ10 is recommended to patients taking some prescription medications, the coenzyme can make other drugs less effective. Discuss the use of CoQ10 supplements with your doctor if you are currently taking any of the following medications:

  • Chemotherapy drugs, including taxol, avastin, and cytozan. Not all chemo medications have adverse reactions to CoQ10.
  • Blood thinners, like warfarin and plavix (clopidigrel)

Some medications reduce CoQ10 levels in the body and can make the supplement less effective. These include:

  • Statins prescribed to lower cholesterol, such as Simvastatin, Crestor, Lipitor, etc.
  • Beta-blockers to control blood pressure, like Toprol, Normodyne, Tenormin, etc.
  • Cholesterol medications like gemfibrozil
  • Tricyclic antidepressants, such as Sinequan, Tofranil, etc.

Individuals who are currently taking prescription medications to lower their blood pressure may be able to decrease their dosage by adding a daily CoQ10 supplement to their routine. Patients with diabetes should discuss their medications with a physician as well before taking coenzyme Q10.

Unlike many vitamins and dietary supplements, there are very few coenzyme Q10 side effects and it is rare for individuals to experience adverse reactions while taking the supplement. It is still a good idea to discuss this treatment option with your physician and to make sure he or she is aware of all other medications and supplements you are currently taking. If you experience any CoQ10 side effects that are not mentioned here, contact your doctor immediately.