Background: Abnormal glucose regulation (AGR) is common and an adverse risk factor in patients presenting with acute coronary syndromes (ACS).Methods: We prospectively evaluated the prevalence of AGR in 300 ACS patients. Fasting blood glucose (BGL), glycated haemoglobin (HbA1c) and urinary albumin creatinine ratio (ACR) were performed. Patients without diabetes completed an oral glucose tolerance test (OGTT) >= 4 weeks post-discharge.Results: On admission, AGR prevalence was 60%; 32% (n = 94) with diabetes and 28% (n = 83) with IFG. OGTT completed in 157 patients, detected new diabetes in 5% (n = 8), IGT in 24% (n = 37), and IFG in 6% (n = 10). In 91 patients with normal admission fasting BGL, 25% (n = 23) had AGR on OGTT. Conversely, in 62 patients with admission IFG, 50% (n = 31) had a normal OGTT. Patients with versus those without AGR on OGTT had higher adjusted geometric mean HbA1c (5.92; 95% CI 5.81-6.02 vs. 5.66; 95% CI, 5.59-5.74, P = 0.001) and urinary ACR (1.38; 95% CI, 0.99-1.91 vs. 0.74; 95% CI, 0.58-0.94, P = 0.003) levels.Conclusions: AGR is present in the majority of ACS patients and unrecognised in up to half of cases. OGTT improves the detection of AGR. Crown Copyright (C) 2008 Published by Elsevier Ireland Ltd. All rights reserved.