A combined rapid acting-long acting insulin formulation has been developed in which the pH of the rapid acting insulin is decreased so that the long acting 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 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. As a result, a patient using intensive insulin therapy should only inject three, rather than four, times a day.