Subcutaneous Fast-Acting Insulin Dosing for Adults
For insulin-naïve adults initiating subcutaneous fast-acting insulin (aspart, lispro, or glulisine), start with 10 units or 0.1-0.2 units/kg body weight, divided into doses administered immediately before meals (0-15 minutes prior). 1, 2
Initial Dosing Strategy
Starting dose:
- 10 units total daily dose is the standard starting point for most insulin-naïve adults 1, 2
- Alternatively, calculate 0.1-0.2 units/kg of body weight for the total daily dose 1, 2
- Divide this total dose across meals where fast-acting insulin will be administered 1, 2
Timing of Administration
Critical timing considerations:
- Administer 0-15 minutes before meals for optimal postprandial glucose control 3
- Fast-acting analogues (lispro, aspart, glulisine) have onset of action at 15 minutes, peak between 30-70 minutes, and duration of 2-5 hours 3
- This represents a significant advantage over regular human insulin, which requires 30-45 minute pre-meal administration 4
Dose Titration Protocol
Systematic adjustment approach:
- Increase by 2 units if 50% of fasting fingerstick glucose values exceed target (90-150 mg/dL) over a 1-week assessment period 1, 2
- Decrease by 2 units if more than 2 fasting fingerstick values per week fall below 80 mg/dL 1, 2
- Evaluate glycemic control every 2 weeks and adjust accordingly 1
- For any hypoglycemic event without clear cause, reduce the corresponding dose by 10-20% 2
Monitoring Requirements
Essential glucose monitoring:
- Check blood glucose at least 4 times daily: before breakfast, before dinner, at bedtime, and when suspecting hypoglycemia 1
- Target fasting glucose of 90-130 mg/dL 1
- Target peak postprandial glucose <180 mg/dL 1
- Never skip bedtime testing to prevent nocturnal hypoglycemia 1
Safety Considerations and Common Pitfalls
Hypoglycemia prevention:
- Hypoglycemia is the most common adverse effect of insulin therapy 1, 2
- Patients must maintain consistent meal timing when using fast-acting insulin 2
- Do not skip meals after insulin administration 2
- Always carry quick-acting carbohydrates 2
Injection site considerations:
- Abdominal injection provides faster absorption than thigh injection 3
- Time to insulin normalization increases by 1 hour with thigh injection versus abdomen (compared to 2-3 hours for regular insulin) 3
Comparative Effectiveness
All three rapid-acting analogues perform similarly:
- Lispro, aspart, and glulisine demonstrate comparable glucose control with similar HbA1c outcomes 5, 6
- These analogues can be used interchangeably in clinical practice 5, 6
- All provide superior postprandial glucose control compared to regular human insulin 7
When Initial Therapy Fails
Escalation strategies if A1C remains above goal: