Introduction. Patients with diabetes mellitus are at risk of hypoglycaemia, which can lead to irreversible consequences. Objective: to evaluate the prevalence of hypoglycaemia, depending on the type of diabetes, treatment method and plasma glucose control. Material. 263 patients, including 67 with type 1 diabetes mellitus, and 196 with type 2. Mean age 59 ± 16 years, duration 12 ± 9 years, body mass index (BMI) 29 ± 6 kg/m². Methods. Subjects completed a questionnaire inclu­ding demographic data, information on treatment,  and the occurrence of hypoglycaemia (mild vs. severe). Results. Over the last year, 855 hypoglycaemic episodes occurred in 107 (41%).The incidence of hypoglycaemia is significantly higher in patients with type 1 com­pared to type 2 diabetes (61% vs. 34% respectively, p < 0.001). In patients with type 2 diabetes treated with insulin compared to those treated with oral drugs, hypoglycaemia occurred in a significantly higher num­ber of subjects (66% vs. 20%, p < 0.001). Hypoglyca­emia was reported in a significantly more frequent in type 1 and mean plasma glucose more than 154 mg/dl vs. below 154 mg/dl over the last year (71% vs. 52%, respectively, p < 0,05). Conclusions. The results indicate the need for mo­dification of educational programs and a greater intensification of treatment guidelines, so that plasma glucose control is not obtained at an expense of an increase in the incidence of hypoglycaemia.