Diabetes is an important medical problem in sub-Saharan Africa. It has traditionally been diagnosed by means of fasting plasma glucose, random blood glucose or an oral glucose tolerance test. Each of these has limitations and, in 2009, an expert committee of the American Diabetes Association recommended using the haemoglobin A1c (HbA1c) to diagnose diabetes mellitus.1 The aim of this paper is to analyse the advantages and disadvantages of using HbA1c as a diagnostic method for diabetes, and its applicability in the South African setting.Keywords: diabetes, glycated haemoglobin, fasting plasma glucose, oral glucose tolerance test