Coenzyme Q10 supplementation of up to 3,000 milligrams is generally safe for daily consumption for extended periods of time, but may affect blood sugar levels, and it may cause nausea, upset stomach, vomiting and low blood pressure, according to Mayo Clinic. CoQ10 may also cause skin rashes in certain individuals, states WebMD.
Other possible side effects of CoQ10 include abnormal breathing, back pain, changes in attention, dizziness, sore throat and loss of appetite, according to Mayo Clinic. Fatigue, flu-like symptoms, sinus inflammation, chest pain and irritability are also possible side effects. For individuals with liver problems, CoQ10 in doses of more than 300 milligrams per day may affect liver enzyme levels. For individuals with mitochondrial disorders, CoQ10 may exacerbate mobility issues.
Headaches are a possible side effect for individuals who suffer from migraines, and for those with bleeding disorders, CoQ10 may augment bleeding risks, states Mayo Clinic. CoQ10 can also alter thyroid hormone levels in individuals with thyroid problems and may negatively interact with thyroid drugs, such as Synthroid.
CoQ10 may decrease the effectiveness of certain chemotherapy drugs, and therefore chemotherapy patients should take the supplement with caution, states WebMD. CoQ10 can also interact with Warfarin by decreasing its effectiveness in prevent clotting. If taken with high blood pressure medications. CoQ10 may cause blood pressure to decrease too much.