In children with type 1 diabetes glucose deterioration occurred every day and night leading into low satisfaction with treatment. Unstable glycemic profile resulting in high glycemic variability depends on the adjustment of insulin dosing to the current needs of the organism. The calculation of prandial insulin dosing is a complex process which involves such factors as preprandial blood glucose level, the amount of food taken, the glycemic index of carbohydrates, the insulin/carbohydrate exchange ratio, the active insulin level following the previous bolus. Currently, in patients treated with continuous subcutaneous insulin infusion (CSII) insulin pumps are equipped with bolus calculators which help to calculate prandial insulin dosing and thus contribute to improve post-prandial blood glucose levels.