Understanding the distinct characteristics, screening guidelines, and essential considerations in the diagnosis of diabetes is crucial for effective management and risk reduction. Type 1 diabetes frequently arises in childhood, with hallmark symptoms of polyuria, polydipsia, weight loss, and ketoacidosis. Type 2 diabetes accounts for most diabetes cases, often occurring in adults with metabolic syndrome or genetic risk factors. Screening asymptomatic adults is vital for early identification. Standards and guidelines advise screening all adults ≥35 years every 3 years, plus more frequent testing for those with obesity, a family history, or other risk factors. Preferred screening modalities include glycosylated hemoglobin, fasting plasma glucose, or a 2-hour oral glucose tolerance test. Distinguishing drug-induced hyperglycemia from primary diabetes is also key. Early diagnosis and treatment of diabetes are important to reduce the risk of acute complications and vascular disease.