Diabetic ketoacidosis (DKA) is the most serious emergency in patients with diabetes. With an estimated 100,000 admissions per year in the United States, DKA is also the leading cause of death in children with type 1 diabetes, and accounts for a significant proportion of admissions in adult patients with type 1 and type 2 diabetes. The mainstay in the treatment of DKA involves the continuous intravenous (IV) infusion of regular insulin or the frequent subcutaneous (SC) injections of regular or rapid-acting insulin analogs. Multiple studies have reported successful protocols for insulin administration during the acute management of DKA, but they have failed to address the transition phase from IV to SC maintenance insulin regimen. The American Diabetes Association (ADA) position statement recommends the use of split-mixed insulin combination of regular and intermediate-acting insulin (NPH). This regimen, however, are associated with a high rate of hyperglycemia shortly after discontinuation of IV insulin and a risk of hypoglycemia during the hospital stay. Recently, the long-acting "basal" insulin glargine (Lantus®, Sanofi Aventis Pharmaceuticals) has been shown to facilitate glycemic control with lower rate of hypoglycemic events than intermediate-acting insulin in subjects with type 1 and type 2 diabetes. This study aims i) to determine the effects of giving a dose of glargine insulin shortly after starting an intravenous insulin infusion on glycemic control, time to resolve DKA, and rate of hypoglycemia in patients with DKA, and ii) to compare the safety and efficacy of basal/bolus (glargine/glulisine) insulin versus the standard split-mixed insulin regimen of NPH and regular insulin after the resolution of DKA. The hypothesis is that basal (lantus®) insulin as compared to NPH insulin shortly after the start of insulin infusion will improve inpatient glycemic control in patients with DKA.