Starting Insulin Therapy in Type 2 Diabetes
Recommended Starting Dose and Regimen
For insulin-naive adults with type 2 diabetes, initiate basal insulin at 10 units once daily OR 0.1-0.2 units/kg body weight, administered at the same time each day. 1, 2, 3
Initial Dosing Strategy
- Standard initiation: Begin with 10 units of basal insulin (NPH, glargine, detemir, or degludec) once daily at bedtime 1, 2
- Weight-based dosing: Alternatively, use 0.1-0.2 units/kg/day for patients with mild-to-moderate hyperglycemia 1, 2, 3
- Severe hyperglycemia: For patients with A1C ≥9%, blood glucose ≥300-350 mg/dL, or A1C 10-12% with symptomatic/catabolic features, consider higher starting doses of 0.3-0.5 units/kg/day using a basal-bolus regimen from the outset 1, 2
Titration Protocol
Increase basal insulin by 2-4 units every 3 days until fasting blood glucose reaches 80-130 mg/dL. 1, 2, 4
- If fasting glucose is 140-179 mg/dL: increase by 2 units every 3 days 1, 2
- If fasting glucose is ≥180 mg/dL: increase by 4 units every 3 days 1, 2
- If hypoglycemia occurs without clear cause: reduce dose by 10-20% immediately 1, 2
Foundation Therapy
Continue metformin at maximum tolerated dose (up to 2000-2550 mg daily) when initiating insulin, unless contraindicated. 1, 2
- Metformin combined with insulin reduces total insulin requirements, provides superior glycemic control, and causes less weight gain compared to insulin alone 1, 5
- Consider continuing one additional non-insulin agent initially 1
- Discontinue sulfonylureas when advancing beyond basal-only insulin to prevent hypoglycemia 1, 2
Critical Threshold: When to Add Prandial Insulin
When basal insulin exceeds 0.5 units/kg/day and approaches 1.0 units/kg/day, add prandial insulin rather than continuing to escalate basal insulin alone. 1, 2, 4
Signs of "Overbasalization"
Watch for these clinical signals that indicate need for prandial insulin rather than more basal insulin 1, 2:
- Basal insulin dose >0.5 units/kg/day
- Bedtime-to-morning glucose differential ≥50 mg/dL
- Hypoglycemia episodes
- High glucose variability throughout the day
- Fasting glucose controlled but A1C remains above target after 3-6 months
Adding Prandial Insulin
- Start with 4 units of rapid-acting insulin before the largest meal OR use 10% of current basal dose 1, 2, 6
- Titrate prandial insulin by 1-2 units or 10-15% every 3 days based on 2-hour postprandial glucose readings 1, 2
- Consider decreasing basal insulin when adding significant prandial insulin, particularly with evening meals 6
Patient Self-Management Requirements
Equip patients with self-titration algorithms based on self-monitoring of fasting blood glucose, as this improves glycemic control. 1
- Daily fasting blood glucose monitoring is essential during titration 1, 2
- Provide education on injection technique, site rotation, hypoglycemia recognition/treatment, and sick day management 1, 2
- Rotate injection sites within the same region (abdomen, thigh, or deltoid) to reduce risk of lipodystrophy 3, 5
Common Pitfalls to Avoid
- Never delay insulin initiation in patients not achieving glycemic goals with oral medications, as this prolongs hyperglycemia exposure and increases complication risk 1, 2
- Never discontinue metformin when starting insulin unless contraindicated, as 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, as this causes overbasalization with increased hypoglycemia risk and suboptimal control 1, 2, 4
- Never use sliding scale insulin as monotherapy, as this treats hyperglycemia reactively rather than preventing it 1, 2
Alternative: GLP-1 Receptor Agonist Combination
For patients with cardiovascular or kidney disease or at high cardiovascular risk, consider adding a GLP-1 receptor agonist to basal insulin before advancing to prandial insulin 1, 7: