Aim  To assess the validity of glycated haemoglobin A_1c (HbA_1c) as a screening tool for early detection of Type 2 diabetes.Methods  Systematic review of primary cross‐sectional studies of the accuracy of HbA_1c for the detection of Type 2 diabetes using the oral glucose tolerance test as the reference standard and fasting plasma glucose as a comparison.Results  Nine studies met the inclusion criteria. At certain cut‐off points, HbA_1c has slightly lower sensitivity than fasting plasma glucose (FPG) in detecting diabetes, but slightly higher specificity. For HbA_1c at a Diabetes Control and Complications Trial and UK Prospective Diabetes Study comparable cut‐off point of ≥ 6.1%, the sensitivity ranged from 78 to 81% and specificity 79 to 84%. For FPG at a cut‐off point of ≥ 6.1 mmol/l, the sensitivity ranged from 48 to 64% and specificity from 94 to 98%. Both HbA_1c and FPG have low sensitivity for the detection of impaired glucose tolerance (around 50%).Conclusions  HbA_1c and FPG are equally effective screening tools for the detection of Type 2 diabetes. The HbA_1c cut‐off point of > 6.1% was the recommended optimum cut‐off point for HbA_1c in most reviewed studies; however, there is an argument for population‐specific cut‐off points as optimum cut‐offs vary by ethnic group, age, gender and population prevalence of diabetes. Previous studies have demonstrated that HbA_1c has less intra‐individual variation and better predicts both micro‐ and macrovascular complications. Although the current cost of HbA_1c is higher than FPG, the additional benefits in predicting costly preventable clinical complications may make this a cost‐effective choice.