Side effects reported with coenzyme Q10 use are not typically serious, are usually mild and brief, stopping without any treatment needed. Such reactions may include nausea, vomiting, stomach upset, heartburn, diarrhea, loss of appetite, skin itching, rash, insomnia, headache, dizziness, irritability, increased light sensitivity of the eyes, fatigue, or flu-like symptoms.

The use of CoQ10 may decrease blood sugar levels, so caution is recommended for patients with diabetes, hypoglycemia, or any similar conditions, as well as for those taking drugs, herbs, or supplements of any kind that affect blood sugar. Blood glucose levels may need to be monitored by a healthcare provider, and to continue using the supplement, adjustments in medication may be required.

Low blood platelet number has been reported in one person taking it. However, it is not known whether other factors (viral infection, current medications, etc.) may have been responsible. The lowering of blood platelets may increase the risk of bruising or bleeding, although there are no known reports of bleeding caused by coenzyme Q10 use. Caution is advised in people who have bleeding disorders or who are taking blood-thinners or any other medications which may increase the risk of bleeding. Changes in medication or dosage may be necessary.



Use of the supplement may decrease blood pressure, therefore discretion is advised for patients with low blood pressure or those who are taking medication for blood pressure conditions. Elevated liver enzymes have been reported in rare occasions, and caution is recommended for those with liver disease or who are taking medications which may do harm to the liver. CoQ10 use may lower levels of cholesterol or triglycerides in the blood. According to one study, thyroid hormone levels may also be affected.

Intense exercise is discouraged for those who use coenzyme Q10. Although its role is not clear, one study has reported organ damage due to lack of oxygen and/or blood flow during such exercise in patients with heart disease.

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