An apparatus for determining factors for insulin therapy comprising: a memory device for storing at least one data set in a memory device, the data set comprising blood glucose readings for, respectively, substantially the beginning (BG an) of and substantially the end (BG an+1) of a selected period of time, a value (Carb an) corresponding to the patient's food intake for the selected period, and the amount of insulin (Ins an) administered to the patient during the selected period; a processing device connected to the memory device and being programmed to calculate a delta blood glucose level (Δ BG an) corresponding to the difference (BG an+1 - BG an) between the blood glucose readings taken, respectively, at substantially the beginning of and substantially the end of the selected period, characterized by the processing device being programmed to determine a correct insulin amount (CorrIns an) corresponding to the delta blood glucose level (Δ BG an) divided by an insulin sensitivity factor, and added to the amount of insulin (Ins an) administered to the patient during the selected period, to determine a plurality of daily carbohydrate to insulin ratios (CIR an) corresponding to respective ones of a plurality of days, the daily carbohydrate to insulin ratios (CIR an) each being based on the correct insulin amount (CorrIns an) and the value (Carb an) corresponding to the patient's food intake for the selected period from the data set of the corresponding one of the plurality of days, and use the carbohydrate to insulin ratios (CIR an) to determine a calculated carbohydrate to insulin ratio, and whereby an insulin dose is determined by dividing the patient's food intake (Carb an) for a selected period by the carbohydrate to insulin ratio, and adding a value corresponding to a difference between a measured blood glucose reading and a target glucose reading that is divided by the insulin sensitivity factor. a memory device for storing at least one data set in a memory device, the data set comprising blood glucose readings for, respectively, substantially the beginning (BG an) of and substantially the end (BG an+1) of a selected period of time, a value (Carb an) corresponding to the patient's food intake for the selected period, and the amount of insulin (Ins an) administered to the patient during the selected period; a processing device connected to the memory device and being programmed to calculate a delta blood glucose level (Δ BG an) corresponding to the difference (BG an+1 - BG an) between the blood glucose readings taken, respectively, at substantially the beginning of and substantially the end of the selected period, characterized by the processing device being programmed to determine a correct insulin amount (CorrIns an) corresponding to the delta blood glucose level (Δ BG an) divided by an insulin sensitivity factor, and added to the amount of insulin (Ins an) administered to the patient during the selected period, to determine a plurality of daily carbohydrate to insulin ratios (CIR an) corresponding to respective ones of a plurality of days, the daily carbohydrate to insulin ratios (CIR an) each being based on the correct insulin amount (CorrIns an) and the value (Carb an) corresponding to the patient's food intake for the selected period from the data set of the corresponding one of the plurality of days, and use the carbohydrate to insulin ratios (CIR an) to determine a calculated carbohydrate to insulin ratio, and whereby an insulin dose is determined by dividing the patient's food intake (Carb an) for a selected period by the carbohydrate to insulin ratio, and adding a value corresponding to a difference between a measured blood glucose reading and a target glucose reading that is divided by the insulin sensitivity factor.