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Harmful Side Effects of CoQ10

By Faith Davies ; Updated July 27, 2017

Coenzyme Q10 is an antioxidant that is found in the heart, liver, kidneys and pancreas. It is used in alternative medicine to treat conditions including mitochondrial disorders, congestive heart failure, heart attacks, hypertension and Parkinson's disease. Some users have reported side effects.

Types of Side Effects

The most common side effects of CoQ10 are diarrhea, nausea, heartburn, dizziness, headaches, irritability and loss of appetite, according to the Physicians Desktop Reference. Though usually mild, diarrhea and nausea can lead to dehydration if it persists for a number of days, cautions the U.S. National Library of Medicine.


Some patients experience allergic reactions to CoQ10, causing chest pain, shortness of breath, swelling of the face, extremities and skin rashes, cautions the Physicians Desktop Reference.

Drug Interactions

There is a possibility of prolonged or sudden bleeding when CoQ10 is taken with warfarin, warns the University of Maryland Medical Center. CoQ10 has the potential to decrease the effectiveness of chemotherapy drugs, reports the University of Maryland Medical Center.


CoQ10 has the potential to cause dangerous drops in blood pressure in those who are already prone to lower pressure readings, according to RxList.com. The safety of CoQ10 during pregnancy and nursing are unknown.


Many of the gastrointestinal and neurological side effects of coenzyme Q10 are diminished when the supplement is taken in two or three smaller doses throughout the day, suggests RxList.com. Those who are taking any medications that may interact with CoQ10 should consult their doctor before beginning treatment.

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