Initial Insulin Dosing for Adult Type 2 Diabetes
For insulin-naive adults with type 2 diabetes, start basal insulin at 10 units once daily OR 0.1-0.2 units/kg body weight once daily, administered at the same time each day. 1, 2, 3, 4
Starting Dose Selection
Standard initiation (most patients):
- 10 units once daily is appropriate for patients with mild-to-moderate hyperglycemia (A1C <9%) 1, 2, 3
- Alternatively, use 0.1-0.2 units/kg/day based on body weight and degree of hyperglycemia 1, 2, 4
- Continue metformin unless contraindicated, and possibly one additional non-insulin agent 1, 2, 3
Higher starting doses for severe hyperglycemia:
- For patients with A1C ≥9%, blood glucose ≥300-350 mg/dL, or symptomatic/catabolic features, consider 0.3-0.5 units/kg/day as total daily dose 1, 2
- These patients require immediate basal-bolus insulin (both long-acting and mealtime insulin), not basal insulin alone 1, 2
- Split the total dose: 50% as basal insulin once daily, 50% as prandial insulin divided among three meals 1, 2
Dose Titration Algorithm
Systematic uptitration every 3 days based on fasting glucose: 1, 2
- If fasting glucose 140-179 mg/dL: increase by 2 units every 3 days
- If fasting glucose ≥180 mg/dL: increase by 4 units every 3 days
- Target fasting glucose: 80-130 mg/dL
- If hypoglycemia occurs without clear cause: reduce dose by 10-20% immediately 1, 2
Patient self-titration improves outcomes - equip patients with this algorithm and daily fasting glucose monitoring 1, 2, 3
Critical Threshold: When to Stop Escalating Basal 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
Clinical signals of "overbasalization" include: 1, 2
- Basal dose >0.5 units/kg/day
- Bedtime-to-morning glucose differential ≥50 mg/dL
- Hypoglycemia episodes
- High glucose variability throughout the day
At this threshold, start prandial insulin: 1, 2
- Begin with 4 units of rapid-acting insulin before the largest meal OR 10% of current basal dose
- Titrate by 1-2 units every 3 days based on 2-hour postprandial glucose readings
Foundation Therapy Requirements
Metformin must be continued when adding insulin unless contraindicated - this combination reduces insulin requirements, limits weight gain, and improves glycemic control compared to insulin alone 1, 2, 5
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 use sliding scale insulin as monotherapy - scheduled basal insulin with correction doses as adjunct only is superior 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 discontinue metformin when starting insulin unless contraindicated - this leads to higher insulin requirements and more weight gain 1, 2, 5
Administration Guidelines
- Administer subcutaneously into abdomen, thigh, or deltoid at the same time each day 1, 4
- Rotate injection sites within the same region to prevent lipodystrophy 1, 4
- Never dilute or mix insulin glargine with other insulins 1, 4
- Never administer intravenously or via insulin pump 4
Patient Education Essentials
Provide comprehensive education on: 1, 2, 3
- Daily fasting blood glucose monitoring during titration
- Recognition and treatment of hypoglycemia (treat at ≤70 mg/dL with 15 grams fast-acting carbohydrate)
- Proper injection technique and site rotation
- "Sick day" management rules
- Insulin storage and handling