To explore the possibility that the half-life of insulin changes after trauma, five control subjects and 19 severe trauma patients received intravenous glucose (0.5 gm/kg) in 5 minutes to raise rapidly the insulin levels, followed immediately by 300 mg of intravenous diazoxide over 5 minutes to inhibit any further insulin secretion. Serial blood samples were analyzed for immunoreactive insulin, and insulin half-life was calculated. The baseline insulin level was 13.4 +/- 3.8 microU/ml in the trauma group 10.4 +/- 3.1 microU/ml in the control group. During the glucose infusion, insulin levels rose to 177.0 +/- 56.0 microU/ml in the controls and to 127.0 +/- 27.0 microU/ml in the trauma group. The rise in the control subjects was greater (P less than 0.03) than the rise in the trauma patients. After diazoxide, insulin levels fell to 25.0 +/- 6.2 microU/ml and 25.0 +/- 6.6 microU/ml, respectively. Insulin half-life in the control subjects was 5.2 +/- 0.3 min and 3.9 +/- 0.2 min in the trauma group (P less than 0.019).