What is the proper dosing regimen for insulin in patients with diabetes?

Insulin Dosing Regimens for Patients with Diabetes

For patients with diabetes, insulin therapy should be initiated with a weight-based approach, using 0.5 units/kg/day as the typical starting dose for metabolically stable patients, with half administered as basal insulin and half as prandial insulin to optimize glycemic control and reduce mortality risk. 1

Type 1 Diabetes Insulin Dosing

Initial Dosing

• Starting insulin dose is based on weight, typically ranging from 0.4 to 1.0 units/kg/day of total insulin, with 0.5 units/kg/day recommended for metabolically stable patients 1
• Higher doses may be required during puberty, pregnancy, and medical illness 1
• The total daily dose should be divided with approximately 50% as basal insulin and 50% as prandial insulin 1

Delivery Methods

• Most people with type 1 diabetes should be treated with either:
  • Multiple daily injections (MDI) of prandial and basal insulin, OR
  • Continuous subcutaneous insulin infusion (CSII) via insulin pump 1
• Rapid-acting insulin analogs are preferred for prandial coverage to reduce hypoglycemia risk 1
• Automated insulin delivery (AID) systems are preferred when feasible as they improve time in range and reduce hypoglycemia 1

Dose Adjustment Considerations

• Prandial insulin doses should be matched to:
  • Carbohydrate intake (carbohydrate counting)
  • Premeal blood glucose levels
  • Anticipated physical activity 1
• For patients using carbohydrate counting, the carbohydrate-to-insulin ratio can be estimated using:
  • 300 ÷ Total Daily Dose for breakfast
  • 400 ÷ Total Daily Dose for lunch and dinner 2
• Glucose correction factor (for high blood glucose) can be calculated as 1960 ÷ Total Daily Dose 3

Type 2 Diabetes Insulin Dosing

When to Initiate Insulin

• Consider insulin when HbA1c ≥7.5% despite oral medications
• Essential when HbA1c ≥10% despite diet, physical activity, and other antihyperglycemic agents 4

Initial Dosing Approach

• Start with basal insulin at 10 units per day or 0.1-0.2 units/kg/day 1
• Can be used in conjunction with metformin and sometimes one additional non-insulin agent 1
• Long-acting basal analogs (glargine or detemir) are preferred over NPH insulin 1

Intensification

• If basal insulin has been titrated to acceptable fasting glucose but A1C remains above target, consider advancing to combination injectable therapy 1
• When adding mealtime insulin, the recommended starting dose is 4 units, 0.1 units/kg, or 10% of the basal dose 1
• If A1C is <8% when starting mealtime bolus insulin, consider decreasing the basal insulin dose 1

Administration Techniques

Injection Sites and Rotation

• Administer subcutaneously into the abdominal area, thigh, or deltoid 5
• Rotate injection sites to reduce risk of lipodystrophy and localized cutaneous amyloidosis 5
• Use the shortest needles available (4-mm pen needles) to avoid intramuscular injection 1

Timing Considerations

• Basal insulin should be administered at the same time every day 5
• Prandial insulin timing varies based on:
  • Insulin formulation (regular, rapid-acting analog, or inhaled)
  • Premeal blood glucose level
  • Carbohydrate content of the meal 1
• Rapid-acting analogs should typically be administered 0-15 minutes before meals 1

Special Considerations

Monitoring and Adjustment

• Blood glucose monitoring is essential for effective insulin therapy 4
• Use fasting plasma glucose values to titrate basal insulin 4
• Use both fasting and postprandial glucose values to titrate mealtime insulin 4
• Consider continuous glucose monitoring for patients on intensive insulin regimens 1

Common Pitfalls to Avoid

• Intramuscular injection can lead to unpredictable absorption and hypoglycemia, especially with long-acting insulins 4
• Lipohypertrophy from repeated injections at the same site distorts insulin absorption 4
• Abrupt discontinuation of oral medications when starting insulin therapy can cause rebound hyperglycemia 4
• Underestimating insulin needs during illness, stress, or steroid therapy can lead to poor glycemic control 6

By following these evidence-based guidelines for insulin dosing, patients with diabetes can achieve optimal glycemic control while minimizing the risks of hypoglycemia and other complications, ultimately improving mortality outcomes and quality of life.