The authors’ aim was to determine whether admission hyperglycaemia in non-diabetic patients with acute myocardial infarction (AMI) could represent a surrogate for previously undiagnosed abnormal glucose tolerance. Among 200 non-diabetic patients with acute myocardial infarction, 81 had admission glucose <7.8 mmol/l, 83 had admission glucose ≥7.8 mmol/L and <11.1 mmol/L and 36 had admission glucose ≥11.1 mmol/L. By fasting glucose criteria, only 14 patients (7%) were classified as diabetic subjects. Following oral glucose tolerance testing (OGTT), 53 patients (27%) were identified as diabetic subjects and 78 patients (39%) as having impaired glucose tolerance. Abnormal glucose tolerance was evenly distributed across the 3 groups. In multivariable analysis, fasting glucose and HbA1c – but not admission glucose – were independent predictors of abnormal glucose tolerance. As these parameters lack sensitivity, OGTT should be considered in all non-diabetic myocardial infarct patients to detect previously undiagnosed abnormal glucose tolerance.