Hyperglycemic crises of diabetic ketoacidosis and nonketotic hyperglycemia are associated with elevation of counterregulatory hormones and proinflammatory cytokines, markers of lipid peroxidation, and oxidative stress. To investigate if other conditions besides hyperglycemia could evoke such a prompt increase in cytokine levels, lipid peroxidation, and oxidative stress markers, we induced hypoglycemic stress by standard insulin tolerance test and measured proinflammatory cytokines, markers of lipid peroxidation, reactive oxygen species (ROS), and counterregulatory hormones. Insulin tolerance test was performed in 13 healthy male subjects with no history of infection, cardiovascular risk factors, or abnormal glucose. At baseline and at 30, 45, 60, 120, and 240 minutes after insulin injection, the following parameters were measured: glucose, cortisol, corticotropin, epinephrine (EP), norepinephrine (NE), growth hormone, tumor necrosis factor (TNF)-alpha, interleukin (IL) 1beta, IL-6, IL-8, free fatty acids, white blood cells, lipid peroxidation markers by thiobarbituric acid assay, and ROS by dichlorofluorescein method. The peak value of white blood cell count at 120 minutes was significantly associated with the peak values of NE at 30 minutes and cortisol at 60 minutes. By comparing the area under the curve of measured parameters, EP emerged as significant predictor of TNF-alpha (P = .05) and IL-8 (P = .027). Cortisol emerged as predictor of IL-1beta significantly (P = .05). Corticotropin predicted area under the curve of IL-6 with borderline significance (P = .06). In the present study, insulin-induced hypoglycemia in nondiabetic male subjects is associated with increased proinflammatory cytokines (TNF-alpha, IL-1beta, IL-6, and IL-8), markers of lipid peroxidation, ROS, and leukocytosis. Elevations of NE, EP, corticotropin, and cortisol in hypoglycaemia are associated with the elevation of the proinflammatory cytokines and leukocytosis.