CoQ10 is not FDA-approved to treat any medical condition although it is widely available over-the-counter as a dietary supplement and recommended by primary care physicians and specialists alike. Diseases such as neurodegenerative diseases, fibromyalgia, diabetes, cancer, mitochondrial diseases, muscular diseases, and heart failure are associated with decreased circulating levels of CoQ10. Many studies have been performed on the premise that increasing systemic CoQ10 levels in such conditions would allow for the proper functioning of processes that require CoQ10.
A recently published, systematic review showed that supplementation with CoQ10, in addition to standard therapy in patients with moderate-to-severe heart failure, is associated with symptom reduction and reduction of major adverse cardiovascular events. It may also improve functional capacity, endothelial function, and left ventricle contractility in patients with congestive heart failure.
Supplementation has shown promising results in improving endothelial function in several subsets of patients. CoQ10 can improve endothelial function in patients with ischemic left ventricular systolic dysfunction heart failure. Likewise, when compared with placebo, CoQ10 appears to improve endothelial function in the peripheral circulation of type-2 diabetics with hyperlipidemia. Evidence of the routine use of CoQ10 in patients with coronary artery disease apart from congestive heart failure is still scanty.
There is also some evidence that, when combined with selenium, CoQ10 supplementation in healthy elderly patients and elderly patients with diabetes, hypertension, and ischemic heart disease, may decrease cardiovascular mortality risk. Data is conflicting whether CoQ10 may play a role in treating high blood pressure.
Some data suggest that supplementation with moderate-to-high dose CoQ10 in patients with mitochondrial disorders may influence bicycle exercise aerobic capacity.
Supplementation with 300 mg daily for 24 weeks in men with Peyronie disease may decrease penile plaque size, reduce penile curvature, and improve erectile function.
Statin drugs, of note, block the production of an intermediate in the mevalonate pathway, a biochemical pathway that leads to the production of CoQ10. Therefore, many physicians hypothesize that statin drugs may deplete the body of CoQ10. As muscle pain and cramping is such a common adverse effect of statins, they believe this depletion is the culprit. Supplementation with 50 mg twice daily has shown the ability to decrease statin-related mild-to-moderate myalgias, resulting in an increased ability to perform daily activities.
Although most studies have used patients with preexisting medical conditions, one study of healthy participants did show that oral supplementation improved subjective fatigue and physical performance during bicycle exercise routines.
CoQ10 has also shown promise in migraine prophylaxis. A double-blind randomized controlled trial showed 300 mg daily to be safe and superior to placebo for migraine prevention. Another randomized double-blind placebo-controlled trial in a cohort of adult women showed that supplementation of 400 mg per day decreased migraine frequency, severity, and duration. A cohort study of 1550 children and adolescents with headaches found that this population has low CoQ10 levels. Supplementation appeared to decrease headache frequency. One study showed that the use of only 100 mg daily decreased the severity of headaches and the number of headaches per month in migraine sufferers. 
Interestingly, CoQ10 levels may be decreased in those with acute influenza infection. Studies on supplementation in this subset of patients have yet to be done, however.
When supplemented alongside standard psychiatric medical therapy, CoQ10 appears to lessen symptoms of depression in patients with bipolar disorder.
In patients with polycystic ovary syndrome, supplementation may improve fasting blood glucose, insulin levels, and total testosterone levels.
Coenzyme Q10 (CoQ10), also referred to as ubiquinone, is a fat-soluble, vitamin-like molecule found naturally in every cellular membrane in our bodies. It is a normal part of our diet but is also endogenously synthesized. It is essential for the proper transfer of electrons within the mitochondrial oxidative respiratory chain and adenosine triphosphate (ATP) production. CoQ10 can increase the production of key antioxidants such as superoxide dismutase, an enzyme capable of reducing vascular oxidative stress in hypertensive patients. CoQ10 reduces levels of lipid peroxidation via the reduction of pro-oxidative compounds. CoQ10 can enhance blood flow and protect blood vessels via the preservation of nitric oxide.
Supplements offer CoQ10 in either the oxidized form (ubiquinone) or the reduced form (ubiquinol). The bioavailability of a given CoQ10 supplement depends on the lipid carrier it is immersed in and any preservatives added.
The vast majority of studies done on CoQ10 in humans have only evaluated it as an oral supplement. Topical over-the-counter preparations are also available, but studies on this route of administration are limited. One study investigates a topical preparation as a treatment for age-related, skin oxidative damage.
Coenzyme Q10 supplements are generally well-tolerated with only minor and infrequent adverse effects, which may include stomach upset, nausea, vomiting, and diarrhea. Doses of 100 mg per day or higher have been associated with mild insomnia in some individuals. Liver enzyme elevation has been seen in some patients taking 300 mg or more per day, but no liver toxicity has been reported. Supplementation has been shown to be tolerated, even up to 1200 mg/day. Other rare adverse effects have included dizziness, photophobia, irritability, headache, heartburn, and fatigue.
Dietary supplements such as coenzyme Q10 are not strictly regulated by the FDA nor are manufacturers required to prove their safety and purity both before and after release to the markets. However, there are several independent agencies that test supplements for purity, composition, and strength and issue certifications to manufacturers that meet their testing criteria. These agencies do not test every batch that is manufactured, however, and they do not guarantee therapeutic value. Often, manufacturers that have received these agencies’ seal of approval will advertise so on their product packaging.
Studies are limited on CoQ10 use in patients with kidney and liver disease, and therefore, it should be avoided in these patients. Patients using chemotherapeutic drugs should avoid using CoQ10 as well since there is little data on the interaction of CoQ10 with these drugs. Since CoQ10 has been shown to lower fasting blood glucose in some patients, it should be used with caution in those with diabetes and/or patients who are prone to hypoglycemic episodes. CoQ10 use should be avoided in nursing mothers, children, and infants as studies in these populations are lacking.
Many studies have monitored blood levels of CoQ10 to assess the efficacy of supplementation. Average plasma concentrations appear to be about 0.34 to 1.65 micrograms/mL. A toxic blood CoQ10 level has not been determined, mostly because CoQ10 toxicity is absent, even at the highest oral supplementation levels.
CoQ10 is safe as a dietary supplement. Toxicity is unlikely, even up to a daily intake of 1,200 mg/day, although typical dosages studied have been 100 to 200 mg/day.
Coenzyme Q10 is a safe, popular dietary supplement that is continuously being studied as an adjunctive treatment for a variety of medical conditions. With the broad commercial base of the supplement industry and widespread interest in complementary and alternative medicine in the United States, inevitably, many healthcare professionals will encounter patients who are interested in using it and other dietary supplements. As data on this promising supplement continues to grow, it is essential that physicians, nurses, pharmacists, and other healthcare professionals continue to update themselves on its potential as an adjunctive treatment for a variety of medical conditions.
Potential Level I evidence for the use of CoQ10 includes adjunctive treatment for patients with moderate-to-severe congestive heart failure.
Potential Level II evidence includes CoQ10 supplementation for the following indications:
Potential Level III evidence for the use of CoQ10 includes the following indications: