Diabetes mellitus is a common chronic disease, and early diagnosis is essential to prevent cardiovascular and microvascular complications. Family medicine practices follow high-risk individuals longitudinally and occupy a key position in diabetes screening. This case illustrates the consequences of omitting HbA1c and fasting plasma glucose (FPG) screening for years in a patient with multiple cardiovascular risk factors.I.E., a 57-year-old man, presented to his family physician on 07.10.2025 for routine prescription renewal. As no biochemical tests had been performed for a long time, HbA1c and FPG were ordered, revealing HbA1c 14% and FPG 495 mg/dL; the patient was referred to the emergency department. He was hospitalized with insulin-requiring diabetes mellitus, acute kidney injury, and hyponatremia, and discharged after treatment. Retrospective review of electronic records showed that during the previous 5–6 years, he had been repeatedly seen in cardiology and other outpatient clinics with atherosclerotic heart disease, hypertension, hyperlipidemia, heart failure, and COPD, and had undergone four coronary interventions. No further diabetes screening had been performed after an HbA1c value of 5.9% in 2017.This case demonstrates systematic neglect of diabetes screening in both primary and secondary care despite high cardiovascular risk and frequent healthcare encounters.Annual HbA1c/FPG screening should be standard practice for patients with risk factors such as coronary artery disease, hypertension, hyperlipidemia, and obesity. Electronic reminders and prompts within chronic disease follow-up forms stating "at least one HbA1c or FPG per year" may reduce delayed diagnoses and reinforce continuity and holistic care in primary care.Despite guideline recommendations for high-risk groups, workload and problem-oriented visits may lead clinicians to overlook screening, so diabetes may first be diagnosed in the setting of severe hyperglycemia.Failure to use simple and accessible tests in a systematic way can delay diabetes diagnosis for years; strengthening screening processes may help reduce complications and the burden on healthcare systems.