Objective To assess the frequency and possible risk indicators of severe hypoglycemia in insulin-dependent (type I) diabetic patients with impaired kidney function.

Research Design and Methods Retrospective follow-up examination of case subjects and control subjects with mean follow-up periods of 2.9 and 1.3 yr, respectively. The setting was the diabetes center at the Düsseldorf University hospital. Subjects were consecutive type I diabetic patients. Case subjects consisted of 44 patients with initial serum creatinine levels of ≥133 μM and pathological proteinuria. Control subjects consisted of 46 patients with normal serum creatinine levels matched for age, duration of diabetes, and hypertension; 57% of case subjects and 67% of control subjects were being treated with p-blockers. Incidence of severe hypoglycemia (cases/patient-yr) was assessed through an interviewer-administered questionnaire.

Results At comparable levels of HbA_1c (7.9 ±1.8 vs. 7.6 ± 1.1%), case subjects had a fivefold higher incidence of severe hypoglycemic episodes (1.28 vs. 0.25 cases/patient-yr, P <0.02) than control subjects. Within the group with impaired kidney function, patients with severe hypoglycemic episodes had lower HbA1c levels (7.4 ± 1.6 vs. 8.7 ± 2.0%, P <0.03) and a lower body mass index (22.0 ± 3.4 vs. 24.4 ± 3.8 kg/m² P <han those without severe hypoglycemic episodes, whereas serum creatinine levels, body weight-related insulin dosage (U kg⁻¹ day⁻¹), prevalence of blindness, autonomic neuropathy, and treatment with β-blockers were comparable.

Conclusions Type I diabetic patients with impaired kidney function are at an excessively high risk of severe hypoglycemia. In addition to low HbA_1c levels, a low body mass index appears to be a risk indicator for this adverse effect of insulin therapy.