| Level I | Good quality evidence |
Systematic review of RCTs with consistent findings High quality individual RCT |
| Level II |
Limited quality patient orientated evidence |
Systematic review of lower quality studies or studies with inconsistent findings Low quality clinical trial Cohort studies Case-control studies |
| Level III | Other |
Consensus guidelines, extrapolations from bench research, usual practice, opinion, disease-oriented evidence (intermediate or physiologic outcomes only), or case series |
[12] Metformin: Effect of intensive blood-glucose control with metformin on complications inoverweight patients with type 2 diabetes (UKPDS 34). UK Prospective Diabetes Study (UKPDS) Group.Lancet. 1998 Sep 12;352(9131):854-65. Erratum in: Lancet1998 Nov 7;352(9139):1558.http://www.ncbi.nlm.nih.gov/pubmed/9742977
Metformin: South African Medicines Formulary. 12th Edition. Division of Clinical Pharmacology.University of Cape Town. 2016.