Aim. To study the influence of hyperglycemia on the course of ischemic stroke in its acute period. Materials and methods. 116 patients with primary ischemic stroke, associated with arterial hypertension, and with no diabetes mellitus in anamnesis were examined. Fasting blood glucose, glycolyzed hemoglobin, immunoreactive insulin and C-peptide levels were determined. Results. Raised levels of glycemia to 5.31 ± 0.68 mmol/l, C-peptide to 0.90 ± 0.31 nmol/l and decreased level of insulin to 9.38 ± 4.34 mcIU/ml were detected. C-peptide to insulin ratio values were reliably higher in patients with severe course of stroke (by 35.6 %, p < 0.05) and unfavorable outcome of disease (by 39.6 %, p < 0.05). Conclusions. Development of ischemic stroke is accompanied by high blood C-peptide levels against the background of normo-and-hypoinsulinemia, hyperglycemia. Manifestation of disorders is connected with severity and clinical outcome of this disease.