Adjusting Insulin in Adult Patients with Type 2 Diabetes
Start with Basal Insulin and Titrate Aggressively
Begin with 10 units of basal insulin (glargine or degludec) once daily, or use 0.1-0.2 units/kg body weight, and increase by 2-4 units every 3 days based on fasting glucose readings until you reach a target of 80-130 mg/dL. 1, 2
Specific Titration Algorithm for Basal Insulin:
- If fasting glucose ≥180 mg/dL: Increase by 4 units every 3 days 1, 2
- If fasting glucose 140-179 mg/dL: Increase by 2 units every 3 days 1, 2
- If fasting glucose <80 mg/dL on more than 2 readings per week: Decrease by 2 units 2
- If hypoglycemia occurs: Reduce dose by 10-20% immediately 1, 2
Continue metformin unless contraindicated, as it reduces insulin requirements and improves outcomes. 1, 2
Recognize When Basal Insulin Alone Is Insufficient
Stop escalating basal insulin when the dose exceeds 0.5 units/kg/day—this is your critical threshold. 1, 2 Beyond this point, adding prandial insulin or a GLP-1 receptor agonist is more effective than continuing to increase basal insulin. 1
Clinical Signs of "Overbasalization" (Stop Increasing Basal):
- Basal insulin dose >0.5 units/kg/day 1, 2
- Bedtime-to-morning glucose differential ≥50 mg/dL 2
- Hypoglycemia episodes 1, 2
- High glucose variability 2
- Fasting glucose at target but HbA1c remains elevated after 3-6 months 1
Add Prandial Insulin When Needed
When basal insulin is optimized but HbA1c remains above target, add rapid-acting insulin (lispro, aspart, or glulisine) before the largest meal. 1
Starting Prandial Insulin:
- Initial dose: 4 units before the largest meal, OR 10% of current basal dose 1, 2
- Titration: Increase by 1-2 units (or 10-15%) every 3 days based on 2-hour postprandial glucose readings 1, 2
- Target: Postprandial glucose <180 mg/dL 3
- Timing: Give rapid-acting insulin 0-15 minutes before meals 4, 5
If one mealtime injection is insufficient, progressively add prandial insulin before other meals, moving toward a full basal-bolus regimen (50% basal, 50% prandial split among three meals). 1
Alternative: Add GLP-1 Receptor Agonist Instead of Prandial Insulin
Consider adding a GLP-1 receptor agonist to basal insulin rather than prandial insulin if weight gain and hypoglycemia are concerns. 1 This combination provides potent glucose-lowering with less weight gain and hypoglycemia than intensified insulin regimens. 1, 2
Monitor and Adjust Based on Glucose Patterns
Daily fasting glucose monitoring is essential during titration. 1, 2 Use fasting glucose to adjust basal insulin and postprandial glucose to adjust prandial insulin. 1
Pattern-Based Adjustments:
- High fasting glucose: Increase basal insulin 2
- High postprandial glucose: Increase prandial insulin before that meal 1, 2
- Nocturnal hypoglycemia with morning hyperglycemia: Consider splitting basal insulin to twice daily 2
Reassess HbA1c every 3 months during active titration. 2
Critical Pitfalls to Avoid
Do not delay insulin intensification when oral agents fail to achieve targets—this prolongs hyperglycemia exposure and increases complication risk. 1, 2
Do not continue escalating basal insulin beyond 0.5-1.0 units/kg/day without adding prandial coverage—this causes overbasalization with increased hypoglycemia and suboptimal control. 1, 2
Do not use sliding scale insulin as monotherapy—it is explicitly condemned by all major guidelines and treats hyperglycemia reactively rather than preventing it. 2, 3
Do not abruptly discontinue metformin when starting insulin—continue it unless contraindicated to reduce insulin requirements and improve outcomes. 1, 5
Special Situations Requiring Dose Reduction
Reduce insulin dose by 20% in hospitalized patients on high-dose home insulin (≥0.6 units/kg/day) to prevent hypoglycemia. 2
Use lower doses (0.1-0.25 units/kg/day) in high-risk patients: elderly (>65 years), renal failure, or poor oral intake. 2
Reduce dose by 10-20% if any hypoglycemia occurs, and investigate the cause. 1, 2