An injectable formulation containing a combination of a rapid acting insulin and a long acting insulin has been developed wherein the pH of the rapid acting insulin is adjusted so that the long acting insulin, e.g. insulin glargine, remains soluble when they are mixed together. In the preferred embodiment, this injectable basal bolus insulin is administered before breakfast, provides adequate bolus insulin levels to cover the meal, does not produce hypoglycemia after the meal and provides adequate basal insulin for up to 24 hours. Lunch and dinner can be covered by two bolus injections of a fast acting, or a rapid acting or a very rapid acting insulin. Alternatively, through adjustment of the ratio of rapid acting insulin to long acting insulin, the long acting insulin may be shortened to a 12 hour formulation. This rapid and long acting blend is re-administered to the patient at dinner time, providing a safe and effective basal insulin level until morning. As a result, a patient using intensive insulin therapy should only inject three, rather than four, times a day.