Starting Insulin Dose for Adults with Diabetes
For insulin-naive adults with type 2 diabetes, start with 10 units once daily of basal insulin OR 0.1–0.2 units/kg/day, then titrate based on fasting glucose; for prandial insulin, begin with 4 units before the largest meal. 1, 2
Type 2 Diabetes: Basal Insulin Initiation
Starting Dose
- Begin with 10 units once daily administered subcutaneously, typically at bedtime 2
- Alternatively, use 0.1–0.2 units/kg/day as the initial dose 2, 3
- The conservative 10-unit approach is preferred in primary care settings to minimize hypoglycemia risk while establishing a safe starting point 2
Titration Strategy
- Increase by 1 unit per day for NPH, insulin detemir, or glargine 100 units/mL 2
- OR increase by 2–4 units once or twice weekly for NPH, detemir, glargine (100 or 300 units/mL), or degludec 2
- Continue titration until fasting plasma glucose consistently reaches 80–130 mg/dL (4.4–7.2 mmol/L) 2
Maximum Dose Considerations
- Basal insulin can be increased up to approximately 0.5–1.0 units/kg/day in some cases 2
- Avoid overbasalization: if fasting glucose fails to improve despite escalating doses, do not continue increasing basal insulin alone—this causes hypoglycemia without improving A1C 1, 2
- Watch for large bedtime-to-morning glucose differentials and high post-prandial-to-pre-prandial differentials, which signal the need for prandial insulin rather than more basal insulin 1
Type 2 Diabetes: Prandial (Regular) Insulin Initiation
When to Add Prandial Insulin
- Consider when A1C ≥10% (≥86 mmol/mol) OR random glucose ≥300 mg/dL (≥16.7 mmol/L) 1
- Add when basal insulin is optimized to goal but A1C remains above target 1
Starting Dose
- Begin with 4 units subcutaneously before the largest meal 1
- OR use 10% of the current basal insulin dose if basal insulin is already being taken 1
Titration Protocol
- Increase by 1–2 units every 3 days OR by 10–15% of the current dose 1
- Guide adjustments using fasting and 2-hour post-prandial glucose readings 1
- Target post-prandial glucose <140 mg/dL (7.8 mmol/L) 1
Type 1 Diabetes: Total Daily Dose
Initial Dosing
- Start with 0.25–1.0 units/kg/day as total daily insulin dose 4
- For replacement therapy (basal-bolus regimen), use 0.6–1.0 units/kg/day 3
Distribution
- 50% as basal insulin (given once or twice daily) 3
- 50% as bolus insulin, divided before breakfast, lunch, and dinner 3
Special Populations
Overweight/Obese Patients with Type 2 Diabetes
- A higher starting dose of 0.3 units/kg/day is as safe as the standard 0.2 units/kg/day dose in overweight/obese patients (BMI 25–40 kg/m²) 5
- The higher dose achieves fasting glucose targets faster (4.53 vs 5.51 weeks to reach <5.6 mmol/L) with comparable hypoglycemia rates 5
Combination with Oral Agents
- Insulin monotherapy: 0.40 units/kg/day to achieve 20% glucose reduction 6
- Insulin + metformin: 0.37 units/kg/day 6
- Insulin + metformin + pioglitazone: 0.35 units/kg/day 6
- Continue metformin when possible, as it reduces all-cause mortality and cardiovascular events in overweight patients 3
Hypoglycemia Management
- If hypoglycemia occurs without obvious cause (missed meal, increased activity, dosing error), reduce the corresponding insulin dose by 10–20% 1
- Prescribe glucagon for emergency use in patients at risk of severe hypoglycemia 1
Monitoring Requirements
- Fasting plasma glucose: guides basal insulin adjustments 1
- 2-hour post-prandial glucose: guides prandial insulin titration 1
- A1C every 3 months until target reached, then every 6 months 1
- Hypoglycemia assessment at every clinical visit 1
Critical Pitfalls to Avoid
- Never continue escalating basal insulin if fasting glucose plateaus—this is overbasalization and increases hypoglycemia without improving glycemic control 1, 2
- Always match syringe to insulin concentration: use U-100 syringes with U-100 insulin; in regions with U-40 insulin, use U-40 syringes 1
- Do not mix regular insulin with lente insulins or insulin glargine; when mixing with NPH, draw regular insulin first 1