The most concerning adverse reaction with HMG-CoA reductase inhibitors (statins) is myotoxicity. Statins inhibit the production of mevalonate, a precursor of both cholesterol and coenzyme Q10, a compound believed to be crucial for mitochondrial function and the provision of energy for cellular processes. There is speculation that a reduction in coenzyme Q10 concentrations may promote the myopathies that have been associated with statin treatment as a result of mitochondrial damage. Although studies have repeatedly demonstrated a reduction in circulating coenzyme Q10 concentrations with statin therapy, it is unclear as to whether tissue levels of coenzyme Q10 are significantly affected. Coenzyme Q10 supplementation has been shown to reverse statin-induced decreases in circulating coenzyme Q10 concentrations, although the effect of supplementation on tissue coenzyme Q10 concentrations and any resulting clinical benefit has not been adequately assessed. Although there is not much of a safety concern with coenzyme Q10 supplementation, there is also not enough evidence to support its routine use for preventing the adverse effects of statin therapy, and it is therefore not recommended for this purpose at this time.