Worldwide epidemiological data indicates insufficient diagnosis of diabetes as an increasing problem of public health. Searching for solutions in this disadvantageous situation, occupational medicine health services seem to open up a unique opportunity to recognize some abnormalities in early steps, especially among the asymptomatic working-age population. 316 workers underwent obligatory prophylactic examinations. In patients with twice assayed FGL ≥ 126 mg/dl (7.0 mmol/l) the additional intervention was implemented, including further diagnostic process and therapy in General Practice (GP), followed by examination by an occupational health specialist within 3 months. The diagnosis of previously unknown diabetes was established among 2.5% of examined workers. All patients referred to the GP due to detected glycaemia impairment visited their doctor and finished the diagnostic process, took up therapy constrained by the occupational health physician to show the effects of intervention within 3 months. Prophylactic medical check-ups allow improved compliance and medical surveillance over glycaemia impairment in patients with prediabetes states, unknown diabetes or uncontrolled clinical course of diabetes. Considering fasting glucose level during mandatory prophylactic examination helps effective prevention of diabetes and its complications and thus give public health system benefits.