Bedtime Glargine Dosing
The recommended starting dose of insulin glargine at bedtime is calculated based on body weight and clinical context: 0.2-0.3 units/kg for elderly patients (≥70 years) or those with reduced kidney function (GFR <60 mL/min), 0.4 units/kg for blood glucose 140-200 mg/dL, or 0.5 units/kg for blood glucose 201-400 mg/dL, with approximately 50% of the total daily insulin dose given as basal insulin. 1
Weight-Based Dosing Algorithm
The Endocrine Society provides a structured approach for initiating insulin glargine:
For patients ≥70 years old OR GFR <60 mL/min:
- Calculate 0.2-0.3 units/kg total daily dose
- Give 50% as basal insulin (glargine) once daily at bedtime
- Example: 70 kg patient = 14-21 units total daily dose → 7-10.5 units glargine at bedtime
For patients with blood glucose 140-200 mg/dL:
- Calculate 0.4 units/kg total daily dose
- Give 50% as basal insulin at bedtime
- Example: 70 kg patient = 28 units total daily dose → 14 units glargine at bedtime
For patients with blood glucose 201-400 mg/dL:
- Calculate 0.5 units/kg total daily dose
- Give 50% as basal insulin at bedtime
- Example: 70 kg patient = 35 units total daily dose → 17.5 units glargine at bedtime 1
Timing Considerations
Glargine is administered once daily at the same time each day. While bedtime dosing is traditional, the FDA label confirms that glargine can be given at pre-breakfast, pre-dinner, or bedtime with similar efficacy 2. However, for older adults, switching from bedtime to morning administration is recommended to reduce nocturnal hypoglycemia risk 3, 4.
Titration Strategy
After initiating glargine:
- Adjust dose by 2 units based on fasting glucose readings over one week
- Target fasting glucose: 90-150 mg/dL (may adjust based on patient health status)
- If ≥50% of fasting values exceed goal → increase by 2 units
- If >2 fasting values/week <80 mg/dL → decrease by 2 units 1, 3, 4
Critical Pitfalls to Avoid
Do NOT use rapid- or short-acting insulin at bedtime - this significantly increases nocturnal hypoglycemia risk 3, 4. Bedtime correction doses should use only half the usual supplemental insulin amount 1.
Avoid sliding scale insulin as sole therapy - the Endocrine Society explicitly recommends against prolonged use of sliding scale insulin alone, as it increases hyperglycemia risk 3-fold 1.
Watch for overbasalization - if bedtime-to-morning glucose differential exceeds 50 mg/dL or significant postprandial hyperglycemia occurs, the patient needs prandial insulin or GLP-1 RA addition rather than more basal insulin 5.
Special Populations
Converting from NPH insulin: Patients previously on twice-daily NPH should receive glargine at 80% of total NPH dose (20% reduction) to minimize hypoglycemia risk 2, 6.
Insulin-naive patients on oral agents: Start with the weight-based calculation above, discontinuing oral agents except metformin (if GFR ≥45 mL/min) 1.
Critically ill patients: While once-daily dosing is standard, emerging evidence suggests twice-daily glargine may reduce predose hyperglycemia without increasing hypoglycemia in ICU settings, though this requires further validation 7.
The evidence consistently supports weight-based dosing over arbitrary fixed doses, as this approach accounts for individual insulin sensitivity and reduces both hyper- and hypoglycemia risk 1.