Initial insulin dosage
Patients with type 1 diabetes should initially be started on a multiple daily injection (basal–bolus) insulin regimen. This regimen achieved optimal blood glucose concentrations in the Diabetes Control and Complications Trial1.
For a multiple daily injection (basal–bolus) insulin regimen, basal insulin is given once or twice daily at the same time each day, usually before bedtime (if once daily) or before breakfast and at bedtime (if twice daily). Bolus insulin is given before meals.
Total daily insulin requirement for a healthy adult is about 0.5 to 0.8 units/kg. For a patient with newly diagnosed type 1 diabetes who does not have diabetic ketoacidosis, a typical initial total daily insulin dose is 0.3 to 0.4 units/kg daily. However, the starting dose varies because insulin deficiency is usually only partial in patients with newly diagnosed type 1 diabetes. The dosage also depends on the patient’s blood glucose concentration and the degree of metabolic decompensation.
A typical regimen for the basal component of a multiple daily injection (basal–bolus) insulin regimen in adults with type 1 diabetes is:
long-acting insulin (approximately 40% of total daily insulin dose) subcutaneously, once or twice daily at the same time each day (see Action profiles of insulin formulations for insulin formulations).
Long-acting insulin is generally preferred over intermediate-acting insulin as the basal component for patients with type 1 diabetes.
A typical regimen for the bolus component of a multiple daily injection (basal–bolus) insulin regimen in adults with type 1 diabetes is:
1rapid-acting insulin (approximately 60% of total daily insulin dose) subcutaneously, given in divided doses up to 15 minutes before meals (faster-acting insulin aspart [Fiasp] is given up to 2 minutes before meals2). Divide the daily dose of rapid-acting insulin between meals according to carbohydrate content. See Action profiles of insulin formulations for insulin formulations
OR
2short-acting insulin (approximately 60% of total daily insulin dose) subcutaneously, given in divided doses up to 30 minutes before meals. Divide the daily dose of short-acting insulin between meals according to carbohydrate content. See Action profiles of insulin formulations for insulin formulations.
Rapid-acting insulin is generally preferred over short-acting insulin as the bolus component because it reduces the postprandial rise in blood glucose concentration and the risk of overnight hypoglycaemia. Short-acting insulin may be used with specialist advice in certain situations (eg patients with diabetes-related gastroparesis, patients with glucocorticoid-induced hyperglycaemia).
Although the product information for rapid-acting insulins states that they can be administered after starting a meal, administration before meals is preferred. While giving the dose after starting a meal allows for more accurate calculation of carbohydrates actually consumed, and reduces the risk of hypoglycaemia if meals are delayed, this approach has a risk of early postprandial hyperglycaemia and delayed hypoglycaemia, due to delayed insulin onset. Administering rapid-acting insulin after a meal may be beneficial in patients with poor or variable oral food intake (eg frail, unwell or hospitalised patients).
If converting from a mixed insulin regimen to a multiple daily injection (basal–bolus) insulin regimen, see Mixed insulin regimen for adults with type 1 diabetes.