Generally, oral CoQ supplementation is well tolerated. The most common side effects are gastrointestinal symptoms (nausea, vomiting, appetite suppression, and abdominal pain), rashes, and headaches. Some adverse effects, largely gastrointestinal, are reported with intakes. Doses of 100-300 mg per day may induce insomnia or elevate liver enzymes. The observed safe level risk assessment method indicated that the evidence of safety is acceptable at intakes up to 1200 mg per day.
Use of CoQ supplementation is not recommended in people with liver or kidney disease, during pregnancy or breastfeeding, or in the elderly.