P (Participants)  Patient with type 2 diabetes mellitus
I (Intervention)  Coenzyme Q10 with no limits on the type, dose, frequency and so on
C (Comparisons)   Western medicine, blanks or placebo
O (Outcomes)     Primary: glycosylated hemoglobin, fasting blood glucose, fasting insulin, adverse events
         Secondary: HOMA-IR, blood lipids, adiponectin
S (Study type)      Randomized controlled trials (RCTs) assessing the effects of coenzyme Q10 for the treatment of type 2 diabetes    mellitus (with no limits on the manner by which randomization has been achieved, on blinding or on the language of publication)
Box 1: Inclusion criteria.