Coenzyme Q10 (CoQ10) is a naturally occurring fat-soluble organic compound with a structure very similar to that of vitamins E and K.1 It is one of a multitude of compounds that function either as coenzymes or as chemicals essential to a chain of enzyme function.

CoQ10 is vital for mitochondrial function, which controls the production of adenosine triphosphate, the main source of human energy.2 CoQ10 occurs naturally in small quantities throughout the body as a result of biosynthesis of the amino acid tyrosine. Though the entire chain of chemistry involved in this process is quite lengthy and complex, the essential function of CoQ10 is that of a potent antioxidant.1 As an antioxidant, its primary functions involve promoting cell growth and protecting cells from oxidative damage.

CoQ10 is found in the endoplasmic reticulum, vesicles, and most notably the inner membrane of the mitochondrion, where it is an important part of the electron transport chain.3

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CoQ10 was first isolated in 1957. It was not until 1972, however, that an application to human illness was noted when Professors Gian Paolo Littarru and Karl Folkers documented a deficiency of CoQ10 in human heart disease.1

Since its discovery and subsequent linkage to heart disease and other conditions, a great deal of emphasis has been placed on studying the potential benefits of CoQ10 supplementation. As of 2002, sales of this compound in the United States alone exceeded $200 million.2 It is known that natural CoQ10 levels decrease with age and tend to be low in patients with some chronic diseases (e.g., heart conditions, muscular dystrophies, Parkinson’s disease, cancer, diabetes, and HIV/AIDS). Some prescription drugs, particularly the statins and beta blockers, also have been shown to deplete CoQ10 levels.4

According to the 1994 FDA Dietary Supplement Health and Education Act, CoQ10 is considered a food supplement in the United States. In countries such as Japan, however, CoQ10 has been approved for the treatment of congestive heart failure (CHF) since 1974.2

Technical data

CoQ10 is described chemically as 2, 3-dimethoxy-5-methyl-6-decaprenyl benzoquinone. Because it is found throughout the human body, it has been dubbed as “ubiquinone.”1 Some of its more significant functions occur in the myocardium, and much study has focused on its effect in treating CHF. In a report released by the Agency for Healthcare Research and Quality, a review of all CoQ10 trials involving more than 60 participants followed for at least six months found that the efficacy of CoQ10 in treating heart failure is still undetermined.2

Nevertheless, some patients in other studies experienced dramatic results, with heart size reduced to nearly normal.1 At present, a large study known as the Symptoms, Biomarker Status (BNP), and Long-Term Outcome (Q-SYMBIO) trial is being planned. It will follow more than 500 patients with New York Heart Association class III and IV CHF for more than two years.2 It is hoped that the results from this trial will help answer whether or not the supplementation of CoQ10 is beneficial for these patients.

Neurologically, the data are more impressive. Several randomized, double-blind, placebo-controlled trials have been conducted studying the efficacy of CoQ10 in patients with Parkinson’s disease. The outcomes show impressive lessening of functional decline and improved ability to perform activities of daily living. Because of the low numbers of participants in these studies, however, their level-of-evidence rating is a “B.”2

A single trial of migraine patients using CoQ10 showed a >50% reduction in migraine frequency in more than 47% of patients. Other disease states, such as diabetes and cancer, are also being investigated as potentially treatable with CoQ10. So far, the studies are not promising.2

Dosage and how supplied

Oral dosages ranging from 50-1,200 mg CoQ10 have been used. For treatment of Parkinson’s disease or other neurodegenerative conditions, up to 3,000 mg/day has been used. For cardiovascular conditions (including CHF), 50-200 mg/day is typical.2 The standard dose form is an oil-filled capsule. It should be noted, however, that no recommended daily dose has been established.


No significant side effects have been observed at lower doses. Mild reactions may include nausea, vomiting, GI upset, heartburn, diarrhea, loss of appetite, skin itching, rash, insomnia, headache, dizziness, irritability, increased light sensitivity of the eyes, fatigue, or flulike symptoms. These side effects are typically mild and brief, resolving without treatment.4

At high doses, some mild nausea has occurred, and there is a potential for undesirable lowering of blood sugar levels and BP.4 Because of the lack of significant safety data, CoQ10 is not recommended for children or for pregnant or lactating women unless they are under a clinician’s care.

As for possible drug interactions, CoQ10 may reduce the toxic effects on the heart caused by the chemotherapy medications daunorubicin and doxorubicin. Preliminary studies suggest that CoQ10 may enhance the effectiveness of certain BP medications. It has been reported that CoQ10 may decrease the effectiveness of blood-thinning medications, such as warfarin (Coumadin), necessitating increased doses of the anticoagulant. Finally, CoQ10 supplementation may reduce the heart-related side effects of timolol drops, a beta blocker used to treat glaucoma.5


CoQ10 is one of the more expensive health supplements reviewed to date. The 50-mg capsules range from $20-$50 for a one-month supply.


While no specific data support the benefit of supplementation of CoQ10, it seems logical that in conditions known to deplete natural CoQ10, supplementation would be potentially beneficial. In light of the low to nonexistent safety risks, CoQ10 supplementation should be offered to patients with any of the listed conditions, as well as those taking significant doses of statins.

Ms. Sego is a staff clinician at the Veterans Administration Hospital in Kansas City, Mo., where she practices adult medicine and women’s health. She also teaches at the nursing schools of the University of Missouri and the University of Kansas.


1. Langsjoen PH. Introduction to coenzyme Q10. Available at: Accessed September 7, 2007.

2. Bonakdar RA, Guarneri E. Coenzyme Q10. Am Fam Physician. 2005;72:1065-1070.

3. Wikipedia. Coenzyme Q10. Available at Accessed September 7, 2007.

4. Mayo Clinic. Coenzyme Q10. Available at: Accessed September 7, 2007.

5. University of Maryland Medical Center. Coenzyme Q10. Available at: Accessed September 7, 2007.