The U.S. Food and Drug Administration does not strictly regulate herbs and supplements. There is no guarantee of strength, purity or safety of products, and effects may vary. You should always read product labels. If you have a medical condition, or are taking other drugs, herbs, or supplements, you should speak with a qualified healthcare provider before starting a new therapy. Consult a healthcare provider immediately if you experience side effects.


Avoid if allergic or sensitive to CoQ10, idebenone, or related substances.

Side Effects and Warnings

CoQ10 is likely safe when up to 3,000 milligrams is taken by mouth daily for up to eight months in healthy people. Nanoparticular CoQ10 is safe at doses of 300 milligrams daily for up to three months. CoQ10 is safe when taken by mouth daily in recommended doses in people who are about to have heart surgery, or those who have heart disease, gum disease, muscle wasting/weakness, Parkinson's disease, Alzheimer's disease, cancer, diabetes, or HIV/AIDS. CoQ10 is also likely safe in healthy people when taken for exercise performance and in children who have chemotherapy side effects. Idebenone is likely safe in doses of up to 60 milligrams per kilogram daily.

Use cautiously in high doses over a long period of time.

Use cautiously in high doses in people with liver problems. Doses of greater than 300 milligrams daily may affect levels of liver enzymes.

Use cautiously in people who have bile duct blockage or liver dysfunction. These conditions may increase CoQ10 levels.

Use cautiously in people who are taking warfarin. CoQ10 may reduce the effectiveness of warfarin.

CoQ10 may increase the risk of bleeding. Caution is advised in people with bleeding disorders or taking drugs that may increase the risk of bleeding. Dosing adjustments may be necessary.

Use cautiously in people who have skin disorders. CoQ10 may cause skin itching and rashes.

Use cautiously in people who have stomach disorders. CoQ10 may cause nausea, upset stomach, and vomiting.

Use cautiously in people who have mitochondrial disorders. CoQ10 may worsen mobility.

Use cautiously in people who have headache or migraines. CoQ10 may cause headache.

CoQ10 may affect blood sugar levels. Caution is advised in people with diabetes or low blood sugar, and in those taking drugs, herbs, or supplements that affect blood sugar. Blood sugar levels may need to be monitored by a qualified healthcare professional, including a pharmacist, and medication adjustments may be necessary.

CoQ10 may cause low blood pressure. Caution is advised in people taking drugs or herbs and supplements that affect blood pressure.

Use cautiously in people who have thyroid problems or those taking thyroid agents. CoQ10 may affect thyroid hormone levels and interact with thyroid agents (such as Synthroid®).

Use cautiously in people who take heart rate-regulating agents. CoQ10 may affect heart rate.

CoQ10 may also cause abnormal breathing, back pain, bronchitis, changes in attention, changes in sperm motility, cholesterol, chest pain, constipation, coughing, diarrhea, dizziness, fainting, falling, fatigue, flu-like symptoms, fungal skin infection, gas, head pressure, hearing loss, heart attack, heartburn, heart dysfunction, indigestion, insomnia, irritability, light sensitivity, loss of appetite, low energy, lung inflammation, muscle pain, night sweats, reduced g-force tolerance, respiratory tract infection, runny nose, sinus inflammation, sore throat, stomach pain, trembling, urinary infection, and viral infection.

Pregnancy and Breastfeeding

There is a lack of scientific evidence on the use of CoQ10 during pregnancy or breastfeeding.

According to the National Institute of Health's Lactation and Toxicology Database (LactMed), CoQ10 is a normal part of human breast milk. Levels may depend on dietary or other differences.

This evidence-based monograph was prepared by The Natural Standard Research Collaboration