Type 2 diabetes mellitus (T2DM) is a disease associated with increased oxidative stress which results from mitochondrial dysfunction. Coenzyme Q10 (CoQ10) is an essential antioxidant for energy production in mitochondria. The purpose of this randomized double-blind clinical trial study was to evaluate the effects of CoQ10 supplementation on serum values of gamma-glutamyl transferase (GGT), pseudocholinesterase (PchE), bilirubin, ferritin, and high-sensitivity c-reactive protein (hs-CRP) and metabolic syndrome biomarkers in women with T2DM.