CoQ10 Side Effects and Medicine Interactions: Warfarin, Blood Pressure Drugs and Chemotherapy

Read this first

Do not stop, start or change any prescribed medicine because of this page. If you take warfarin, insulin, blood pressure or cholesterol medicines, or you are having cancer treatment or surgery, ask your prescriber or pharmacist before using CoQ10. In a US emergency call 911; for a possible overdose or poisoning call Poison Help at 1-800-222-1222.

The short answer

The NCCIH says no serious side effects of CoQ10 have been reported and mild ones such as insomnia or digestive upsets may occur, but it may interact with warfarin and insulin and may not be compatible with some cancer treatments. [1] Interaction evidence is mixed and often old or small, so a pharmacist who sees your full medicine list is the right person to ask.

Evidence labels used here: mixed, insufficient evidence, evidence of harm (none established for CoQ10 itself in the sources we read), no good evidence of benefit. Amounts are study amounts, not advice. Proper evidence not found means we looked and found nothing usable.

Reported side effects

• The NCI's summary reports mild insomnia at 100 mg a day or higher in some people. [2]
• It reports liver enzyme elevation with 300 mg a day for extended periods, with no liver toxicity reported. [2]
• Other reported effects include nausea, heartburn, headache, upper abdominal pain, dizziness, rashes, irritability, sensitivity to light and tiredness. [3]
• A 2008 safety review concluded CoQ10 has low toxicity and does not cause serious adverse effects in humans. [4]

Medicines and conditions

Cancer treatment: tell your oncology team

The NCCIH says CoQ10 may reduce heart damage from one type of chemotherapy drug, yet may not be compatible with some cancer treatments. [1] The NCI says trials using CoQ10 to prevent treatment toxicity have not followed patients long enough to learn whether it made cancer treatment less effective. [2] In one mouse study, giving CoQ10 with radiation reduced the radiation's effect. [2] In 1,134 patients with breast cancer, using any antioxidant supplement (CoQ10 among them) before and during treatment was linked to a trend toward more recurrence (adjusted hazard ratio 1.41, range 0.98 to 2.04). [2] That study was observational and did not isolate CoQ10. Read more at antioxidants and medicines and antioxidant safety.

Before surgery

The 2015 review's authors said that because supplement effects on clotting are hard to predict, it is prudent to advise stopping supplements before surgery. [9] Whether and when to stop is for your surgical team to decide. NCCIH notes some evidence that CoQ10 may reduce some complications of heart surgery, which is a hospital-supervised setting. [1] See supplements before surgery.

Pregnancy, children, kidney and liver conditions

Proper evidence not found on CoQ10 safety in pregnancy, breastfeeding or children in the NCCIH and NCI pages or our PubMed searches. Kidney conditions are not described in the sources we read. Because liver enzyme rises were reported with long-term use, people with liver conditions should ask a clinician first. [2] See pregnancy and breastfeeding and liver safety.

Quality

In the US, dietary supplements do not require FDA premarket approval unless disease claims are made, and ingredients may vary from lot to lot. [2] See quality testing and the general medication interactions page.