Insulin Dosing Regimens for Type 2 Diabetes
Initial Basal Insulin Dosing
Start with 10 units of basal insulin once daily OR 0.1-0.2 units/kg body weight, administered at the same time each day. 1, 2
For patients with more severe hyperglycemia (A1C ≥9%, blood glucose ≥300-350 mg/dL), consider higher starting doses of 0.3-0.5 units/kg/day as total daily insulin, using a basal-bolus regimen from the outset rather than basal insulin alone. 1, 2
Basal Insulin Titration Algorithm
- If fasting glucose 140-179 mg/dL: Increase basal insulin by 2 units every 3 days 1, 2
- If fasting glucose ≥180 mg/dL: Increase basal insulin by 4 units every 3 days 1, 2
- Target fasting glucose: 80-130 mg/dL 1, 2
- If hypoglycemia occurs: Reduce dose by 10-20% immediately 1, 2
Continue metformin (unless contraindicated) when initiating basal insulin, as this combination provides superior glycemic control with reduced insulin requirements and less weight gain. 1, 2
Critical Threshold: When to Add Prandial Insulin
Stop escalating basal insulin when the dose exceeds 0.5 units/kg/day and add prandial insulin instead. 1, 2
Signs of "Overbasalization" (indicating need for prandial insulin):
- Basal insulin dose >0.5 units/kg/day 1, 2
- Bedtime-to-morning glucose differential ≥50 mg/dL 1, 2
- Hypoglycemia episodes 1, 2
- High glucose variability throughout the day 1, 2
- Fasting glucose controlled but A1C remains above target after 3-6 months 1, 3
Prandial Insulin Initiation and Dosing
Start with 4 units of rapid-acting insulin before the largest meal OR use 10% of the current basal insulin dose. 1, 3
Prandial Insulin Titration Algorithm
- Increase prandial insulin by 1-2 units (or 10-15%) every 3 days based on 2-hour postprandial glucose readings 1, 3
- Target postprandial glucose: <180 mg/dL at 2 hours post-meal 1, 3
- Administer rapid-acting insulin 0-15 minutes before meals for optimal postprandial control 1, 4
Adding Additional Prandial Doses
Once the first prandial insulin dose is optimized, add prandial insulin to other meals as needed based on postprandial glucose patterns. 1, 3 Start each new meal dose at 4 units and titrate using the same algorithm. 3
Full Basal-Bolus Regimen Calculation
For patients requiring immediate basal-bolus therapy (A1C ≥10-12% with symptoms):
Total Daily Dose (TDD): 0.3-0.5 units/kg/day 1, 2
Distribution:
Example for 70 kg patient with severe hyperglycemia:
- TDD = 0.4 units/kg × 70 kg = 28 units
- Basal insulin: 14 units once daily
- Prandial insulin: ~5 units before each of three meals
Monitoring Requirements
- Daily fasting blood glucose during titration phase 1, 2
- 2-hour postprandial glucose after meals where prandial insulin is given 1, 3
- Reassess every 3 days during active titration 1, 2
- Reassess every 3-6 months once stable with A1C measurement 1, 2
Common Pitfalls to Avoid
Never delay insulin initiation in patients not achieving glycemic goals with oral medications—this prolongs hyperglycemia exposure and increases complication risk. 1, 2
Never discontinue metformin when starting insulin unless contraindicated—this leads to higher insulin requirements and more weight gain. 1, 2
Never continue escalating basal insulin beyond 0.5-1.0 units/kg/day without addressing postprandial hyperglycemia—this causes overbasalization with increased hypoglycemia risk and suboptimal control. 1, 2
Never use sliding scale insulin as monotherapy—it is explicitly condemned by all major diabetes guidelines and leads to dangerous glucose fluctuations. 1, 2
Never give rapid-acting insulin at bedtime—this significantly increases nocturnal hypoglycemia risk. 1, 2
Special Populations
Elderly or High-Risk Patients (>65 years, renal failure, poor oral intake)
Use lower starting doses of 0.1-0.25 units/kg/day to prevent hypoglycemia. 1, 2
Hospitalized Patients
- Insulin-naive or low-dose: Start TDD 0.3-0.5 units/kg/day, half as basal 1, 2
- On high-dose home insulin (≥0.6 units/kg/day): Reduce TDD by 20% upon admission 1, 2