Background: Prediabetes is a disordered state of glucose metabolism defined by an elevated blood glucose level that is below the level required for the diagnosis of diabetes. Prediabetes is associated with an increased risk of cardiovascular disease. The onset and progression of macrovascular disease occur during the prediabetes phase. Early diagnosis and screening of prediabetes are essential steps to prevent diabetes and its associated complications. Objective: To assess the prevalence of prediabetes and undiagnosed diabetes in patients with cardiovascular disease according to the ADA criteria. Methods: This cross-sectional study included 2968 a high cardiovascular risk patients aged 40 to 75 years admitted to the Department of Internal Medicine. Sociodemographic variables and other relevant medical history information were collected by the researchers during the clinical interview. A fasting blood sample was obtained to determine HbA1c levels and other relevant laboratory findings. Results: Of the total number of participants, 1496 participants were not diagnosed with diabetes, 485 (32.4%) of them had HbA1c values indicating prediabetes and 158 (10.6%) of them had HbA1c values indicating new diagnosed diabetes. Up to one-third of those with undiagnosed prediabetes had already been diagnosed with cardiovascular complications. Conclusion: Routine screening of glycemic metabolism could be valuable in identifying high-risk individuals before a cardiovascular event occurs.