Introduction There is a known association between hyperglycemia and the presence of coronary syndrome. The purpose of this work is to study risk factors and clinical manifestations of hyperglycemia in patients diagnosed with coronary artery disease. Methods The study was conducted in 2018–2020 among 505 patients in Ho Chi Minh city, Vietnam. Based on the results of the glucose test at 0 and 120 min, the patients were divided into the groups: with normal glucose metabolism (control, 204), patients with impaired fasting glucose levels (175 patients, group 2), and patients with impaired glucose tolerance, including diabetes mellitus (126, group 3). Anthropometric measurements were performed, and the levels of hemoglobin HbA, glucose, lipids were measured. Results In the group of patients with fasting hyperinsulinemia, all variables (body weight, body mass index, waist circumference, LAP, creatinine clearance) differed considerably as compared to the control group ( p ≤ 0.0001). Decrease in tissue sensitivity to insulin is already present at normal levels of glucose metabolism. Conclusions The study found that diabetes mellitus and prediabetes are more typical for patients with metabolic syndrome and acute coronary syndrome. The results obtained will allow predicting the risk of developing coronary syndrome depending on the presence of diabetes mellitus or prediabetes.