Human insulin use and hypoglycaemia: insights from the Pittsburgh Epidemiology of Diabetes Complications Study.

Recently, concern has arisen that human (as opposed to beef or pork) insulin may cause more frequent and/or severe hypoglycaemia in association with reduced warning symptoms. This question was examined from questionnaire data of 628 Type 1 diabetic patients (mean age 28 years and duration of diabetes 19 years) participating in the baseline examination of a follow-up study of diabetes complications. Those using human insulin (n = 73) reported an insignificantly higher frequency of hypoglycaemic reactions in the last year than those using animal insulin (66 vs 55% with reactions at least monthly) and only a weak trend was seen overall for the prevalence of human insulin use to increase with increasing frequency of hypoglycaemia (p = 0.06). Hypoglycaemic reactions resulting in unconsciousness were too rare to permit analysis by type of insulin used. The prevalence of reduced awareness of hypoglycaemia was similar among human insulin users to that seen in animal insulin users (25 vs 19%, NS). However, prevalence of reduced awareness showed a strong relationship to current blood glucose in the animal (r = -0.18, p less than 0.001) but not human (r = -0.06, NS) insulin users. Excluding patients with autonomic symptoms or neuropathy did not alter the results, nor did excluding the 34 individuals taking more than three insulin injections per day. It is concluded that human insulin use is not associated with either any substantial increased frequency of hypoglycaemia or reduction in awareness of hypoglycaemia. However, human insulin use does appear to be associated with reduced awareness of hypoglycaemia in those whose blood glucose control is relatively poor.