Self-monitoring of blood glucose (SMBG) is recognized as necessary in insulin-treated diabetic patients. There is less evidence for the regular use of SMBG in non-insulin-using type 2 diabetic patients. The rationale for an appropriate regimen of SMBG might be to have at least one time-point of monitoring included within each of the 3 periods of daytime i.e. fasting, postprandial and postabsorptive periods. Interventional trials have indicated that a 4-to 5-point daily profile represents an optimal regimen for SMBG in type 1 diabetic patients with satisfactory diabetic control. This type of SMBG includes 4 daily glucose determinations (3 before each meal and one at bedtime) and one weekly monitoring at 3: 00 am. However additional determinations should be made within postprandial states, particularly when rapid insulin analogues or pump-treatments are used. In non-insulin-using type 2 diabetic patients, studies of diurnal glycemic profiles have indicated that postprandial glucose is an important contributor to HbA1c and that mid-morning hyperglycemia is the "weakest link" of metabolic control. Therefore mid-morning glucose testing should be recommended when HbA1c levels are not correctly controlled. Furthermore, extended postlunch determinations at 5: 00 pm can be helpful for checking both the quality and safety of diabetic control in such patients. The frequency and timing of SMBG depend both on the type (1 or 2) of diabetes and should be a compromise between optimal and minimal regimens.