What are the insulin requirements for Type 1 Diabetes Mellitus (DM) management?

Type 1 Diabetes Insulin Requirements

For adults with type 1 diabetes, start with a total daily insulin dose of 0.5 units/kg/day, divided approximately 50% as basal insulin and 50% as prandial insulin across meals, using multiple daily injections or continuous subcutaneous insulin infusion. 1

Initial Dosing Algorithm

Standard Starting Dose

• Total daily insulin requirement: 0.4-1.0 units/kg/day 1
• Typical starting dose for metabolically stable patients: 0.5 units/kg/day 1
• Distribution: 40-50% as basal insulin, 50-60% as prandial insulin 1, 2

Special Populations Requiring Dose Adjustments

• Honeymoon phase or residual beta-cell function: 0.2-0.6 units/kg/day 1, 2
• Diabetic ketoacidosis presentation: Higher weight-based doses required 1
• Puberty: Significantly higher doses often needed, potentially exceeding 1.0 units/kg/day 1
• Pregnancy and acute illness: Increased requirements 1

Insulin Delivery Methods

Multiple Daily Injections (MDI)

• 3-4 injections per day combining basal and prandial insulin 1
• Long-acting basal analog (glargine, degludec, or detemir) once or twice daily 1
• Rapid-acting analog (lispro, aspart, or glulisine) before each meal 1

Continuous Subcutaneous Insulin Infusion (CSII)

• Approximately 50% of total daily dose as basal infusion, 50% as meal-related boluses 3
• Modest advantages over MDI: 0.30 percentage point lower A1C, reduced severe hypoglycemia 1
• Automated insulin delivery (AID) systems preferred when feasible for improved time in range and reduced hypoglycemia 1

Insulin Type Selection

Basal Insulin

Use long-acting analogs (glargine U-100/U-300, degludec, or detemir) rather than NPH insulin to reduce hypoglycemia risk, particularly nocturnal episodes. 1

Prandial Insulin

Use rapid-acting analogs (lispro, aspart, or glulisine) rather than regular human insulin to reduce hypoglycemia risk and improve postprandial control. 1

• Administer 0-15 minutes before meals 3, 4
• Faster-acting insulin aspart offers enhanced postprandial coverage 1, 5

Prandial Insulin Dosing Strategy

Carbohydrate Counting Education

Patients must be educated to match prandial insulin doses to carbohydrate intake, premeal blood glucose, and anticipated physical activity. 1

• Advanced education on fat and protein impact for those who master carbohydrate counting 1

Timing Considerations

• Rapid-acting analogs: 0-15 minutes before meals 3, 4
• Timing should be individualized based on premeal glucose level 1

Monitoring Requirements

Blood Glucose Monitoring

Daily self-monitoring of blood glucose is essential for all patients receiving insulin therapy. 1, 2

• Continuous glucose monitoring (CGM) should be considered standard of care for most patients with type 1 diabetes 1
• Sensor-augmented pump therapy with threshold-suspend feature reduces nocturnal hypoglycemia without increasing A1C 1

Dose Adjustment Frequency

Reassess insulin doses every 3-6 months or more frequently during active titration. 1

Critical Pitfalls to Avoid

Inadequate Basal Coverage

Do not use basal insulin doses below 40% of total daily insulin in stable patients, as this leads to inadequate between-meal and overnight glucose control. 1, 2

Excessive Basal Insulin

When basal insulin exceeds 0.5-1.0 units/kg/day without achieving glycemic targets, add or optimize prandial insulin rather than continuing to escalate basal insulin alone. 1, 2

• Signs of overbasalization: bedtime-to-morning glucose differential ≥50 mg/dL, hypoglycemia, high glucose variability 1, 2

Delayed Insulin Administration

Administering rapid-acting insulin after meals rather than before significantly impairs postprandial glucose control. 2

Injection Site Neglect

Rotate injection sites within the same region (abdomen, thigh, upper arm, or buttocks) to prevent lipodystrophy, which distorts insulin absorption. 3, 4

Hypoglycemia Management Failure

Immediately reduce insulin dose by 10-20% after any episode of severe hypoglycemia. 1, 2

Glycemic Targets

Standard Targets for Most Adults

• A1C: <7% (53 mmol/mol) 5
• Fasting/preprandial glucose: 80-130 mg/dL (4.4-7.2 mmol/L) 1, 2
• Postprandial glucose (1-2 hours after meals): <180 mg/dL (10.0 mmol/L) 1

Pediatric Targets

For all children with type 1 diabetes, including preschool children: A1C <7.5% (58 mmol/mol) to minimize hyperglycemia, severe hypoglycemia, and long-term complications. 4