As of 2015, the supplement coenzyme Q-10, or CoQ-10, has no proven medical effects, reports MedlinePlus. The Natural Medicines Comprehensive Database rates it likely to be effective in relieving symptoms of natural CoQ-10 deficiency and mitochondrial disorders.
CoQ-10 deficiency is very rare, but taking oral CoQ-10 supplements seems to relieve the fatigue, weakness and seizures that the condition causes, explains MedlinePlus. Although recovery is slow, CoQ-10 appears to improve the symptoms of people with mitochondrial disorders, which impede energy production in cells. When taken alone or with other medications, it may also lessen the risk of a heart attack, lower blood pressure, prevent congestive heart failure and reduce complications during heart bypass surgery. It may lessen nerve damage caused by diabetes, decrease age-related vision loss and prevent migraine headaches. CoQ-10 may also help people with Parkinson's disease, muscular dystrophy, HIV/AIDS and Peyronie's disease, which causes painful erections.
Although CoQ-10 supplements are probably safe for adults, possible side effects include nausea, vomiting, diarrhea and skin rashes, cautions MedlinePlus. Because the supplement may lower blood pressure, people whose blood pressure is already low should monitor it carefully. Children should not take CoQ-10 without the supervision of health care professionals. CoQ-10 may decrease the effectiveness of other medications and blood pressure control during surgery.