Insulin therapy may be initiated as augmentation, starting at 0.3 unit per kg, or as replacement, starting at 0.6 to 1.0 unit per kg. When using replacement therapy, 50 percent of the total daily insulin dose is given as basal, and 50 percent as bolus, divided up before breakfast, lunch, and dinner. Combination of insulin with metformin is indeed associated with better glycemic control, fewer hypoglycemic events, and less weight gain.

In patients with type 2 diabetes mellitus, insulin may be used to augment therapy with oral glycemic medications or as insulin replacement therapy. The American Diabetes Association suggests the use of long-acting (basal) insulin to augment therapy with one or two oral agents or one oral agent plus a glucagon-like peptide 1 receptor agonist when the A1C level is 9% or more, especially if the patient has symptoms of hyperglycemia or catabolism. Insulin regimens should be adjusted every three or four days until targets of self-monitored blood glucose levels are reached. A fasting and premeal blood glucose goal of 80 to 130 mg per dL and a two-hour postprandial goal of less than 180 mg per dL are recommended. Insulin use is associated with hypoglycemia and weight gain. Insulin analogues are as effective as human insulin at lowering A1C levels with lower risk of hypoglycemia, but they have significantly higher cost. Patients with one or more episodes of severe hypoglycemia (i.e., requiring assistance from others for treatment) may benefit from a short-term relaxation of glycemic targets. Several new insulin formulations have been approved recently that are associated with less risk of hypoglycemia compared with older formulations. The goals of therapy should be individualized based on many factors, including age, life expectancy, comorbid conditions, duration of diabetes, risk of hypoglycemia, cost, patient motivation, and quality of life.