Insulin Glargine Dosing in Type 1 Diabetes
Starting Dose
For metabolically stable patients with type 1 diabetes, start with a total daily insulin dose of 0.5 units/kg/day, giving approximately 50% (or one-third to one-half) as insulin glargine once daily and 50% as rapid-acting prandial insulin divided among meals. 1, 2
Calculating the Initial Dose
- Total daily insulin requirement: 0.4-1.0 units/kg/day, with 0.5 units/kg/day being typical for metabolically stable patients 1
- Basal insulin (glargine) component: 40-50% of total daily dose (approximately one-third per FDA labeling) 1, 2
- Prandial insulin component: 50-60% of total daily dose, divided among three meals 1
Example Calculation
For a 70 kg patient with type 1 diabetes:
- Total daily dose: 0.5 units/kg/day × 70 kg = 35 units/day
- Insulin glargine: 17-18 units once daily
- Rapid-acting insulin: 17-18 units total, divided as approximately 6 units before each meal
Special Populations Requiring Dose Adjustments
- Honeymoon phase or residual beta-cell function: May require lower doses of 0.2-0.6 units/kg/day 1
- Puberty, pregnancy, or acute illness: May require higher doses, potentially exceeding 1.0 units/kg/day 1
- Immediately following ketoacidosis: Require higher weight-based dosing 1
Administration Guidelines
- Timing: Administer subcutaneously once daily at the same time each day—morning, evening, or bedtime—whichever is most convenient 1, 2
- Injection sites: Abdomen, thigh, deltoid, or buttock 1, 2
- Site rotation: Rotate injection sites within the same region to prevent lipodystrophy and localized cutaneous amyloidosis 1, 2
- Needle size: Use 4-mm pen needles to minimize risk of intramuscular injection 1
Titration Protocol
Adjust insulin glargine by 2-4 units every 3 days based on fasting blood glucose patterns until reaching a target of 80-130 mg/dL. 1
Specific Titration Algorithm
- If fasting glucose is 140-179 mg/dL: Increase insulin glargine by 2 units every 3 days 1
- If fasting glucose is ≥180 mg/dL: Increase insulin glargine by 4 units every 3 days 1
- If hypoglycemia occurs: Reduce the dose by 10-20% immediately 1
Critical Threshold: When to Stop Escalating Basal Insulin
Stop escalating insulin glargine when the dose exceeds 0.5 units/kg/day and approaches 1.0 units/kg/day; instead, intensify prandial insulin coverage rather than continuing to increase basal insulin. 1
Signs of Overbasalization
- Basal dose >0.5 units/kg/day 1
- Bedtime-to-morning glucose differential ≥50 mg/dL 1
- Hypoglycemia episodes 1
- High glucose variability 1
Special Considerations for Renal Impairment
- CKD Stage 5: Reduce total daily insulin dose by 35-40% in type 1 diabetes 1
- eGFR <45 mL/min/1.73 m²: Titrate conservatively and monitor more closely for hypoglycemia 1
Hypoglycemia Management
- Treatment threshold: Treat any glucose <70 mg/dL immediately with 15 grams of fast-acting carbohydrate 1
- Recheck: Recheck in 15 minutes and repeat if needed 1
- Prevention: All patients must carry at least 15g carbohydrate at all times 1
- Reversing hypoglycemia unawareness: Scrupulous avoidance of hypoglycemia for 2-3 weeks can reverse hypoglycemia unawareness 1
Important Contraindications and Warnings
- Do not mix or dilute: Insulin glargine must not be diluted or mixed with any other insulin or solution due to its low pH 1, 2
- Do not administer intravenously: Only subcutaneous administration 2
- Do not use in insulin pumps: Not approved for continuous subcutaneous insulin infusion 2
- Avoid lipodystrophy areas: Do not inject into areas of lipodystrophy or localized cutaneous amyloidosis, as this causes erratic absorption 1, 2