Separating basal and meal-related insulin requirements allows a systematic approach to subcutaneous insulin therapy. Simple guidelines for both the doctor and patient can cater for the spectrum of severity of diabetes. A non-insulin-dependent diabetic who, despite dieting, continues to have moderate fasting hyperglycaemia (6-10 mmol/l) may need only a basal insulin supplement, whereas a totally insulin-dependent diabetic usually needs similar amounts of basal and meal-related insulin. The likely insulin requirements of individual diabetics can be predicted, including the increased amounts required by obese patients. The algorithms have been developed using ultralente to provide the basal insulin requirement, but the principles and doses probably apply to other similarly long-acting insulins or an insulin pump. The insulin doses can be easily altered for varying lifestyles, including night work, religious fasts or long distance aeroplane travel, and for temporary disturbances such as operations or intercurrent infections.