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% (0.25 units/kg/day) as insulin glargine once daily and 50% as rapid-acting prandial insulin divided among meals. 1
Weight-Based Calculation Algorithm
- Total daily insulin requirement: 0.4-1.0 units/kg/day 1
- Typical starting dose: 0.5 units/kg/day for metabolically stable patients 1, 2
- Basal insulin (glargine) component: 40-50% of total daily dose 1, 3
- Prandial insulin component: 50-60% of total daily dose, divided among three meals 1
Example for a 70 kg patient:
- Total daily dose: 35 units (0.5 units/kg × 70 kg)
- Insulin glargine: 17-18 units once daily
- Rapid-acting insulin: 17-18 units total, divided as ~6 units before each meal
Special Populations Requiring Dose Adjustments
- Newly diagnosed patients or honeymoon phase: May require lower doses of 0.2-0.6 units/kg/day 2
- Puberty: Higher doses up to 1.5 units/kg/day may be required 1, 3
- Immediately following ketoacidosis: Higher weight-based dosing required initially 2
Administration Guidelines
Administer insulin glargine subcutaneously once daily at the same time each day—morning, evening, or bedtime—whichever is most convenient for the patient. 1, 4
- Inject into abdomen, thigh, deltoid, or buttock 1, 4
- Rotate injection sites within the same region to prevent lipodystrophy 1, 4
- Use 4-mm pen needles to minimize risk of intramuscular injection 1
- Never mix or dilute insulin glargine with other insulins 4
Titration Protocol
Adjust insulin glargine by 2-4 units every 3 days based on fasting blood glucose patterns until reaching target of 80-130 mg/dL. 1, 2, 3
Specific Titration Algorithm
- If fasting glucose 140-179 mg/dL: Increase by 2 units every 3 days 2, 3
- If fasting glucose ≥180 mg/dL: Increase by 4 units every 3 days 2, 3
- If hypoglycemia occurs: Reduce dose by 10-20% immediately 2, 3
Critical Threshold for Twice-Daily Dosing
Consider splitting insulin glargine to twice-daily administration when once-daily dosing fails to provide adequate 24-hour coverage, particularly in patients with high glycemic variability or persistent nocturnal hypoglycemia with morning hyperglycemia. 2
- This is more common in type 1 diabetes than type 2 2
- Split the total daily dose into two equal injections 12 hours apart 2
Monitoring Requirements
- Daily fasting blood glucose during titration phase 2, 3
- Pre-meal and 2-hour postprandial glucose to guide prandial insulin adjustments 2
- HbA1c every 3 months during intensive titration 2
Critical Pitfalls to Avoid
Overbasalization
When basal insulin exceeds 0.5 units/kg/day and approaches 1.0 units/kg/day, stop escalating glargine and instead intensify prandial insulin coverage. 1, 2, 3
Clinical signs of overbasalization include:
- Basal dose >0.5 units/kg/day 2
- Bedtime-to-morning glucose differential ≥50 mg/dL 2
- Hypoglycemia episodes 2
- High glucose variability 2
Injection Technique Errors
- Avoid intramuscular injection, which causes unpredictable absorption and frequent hypoglycemia 1
- Risk highest in lean patients injecting into limbs with needles >4 mm 1
- Avoid injecting into areas of lipohypertrophy, which causes erratic absorption 1
Inadequate Prandial Coverage
Type 1 diabetes always requires both basal and prandial insulin—glargine alone is insufficient. 1, 4
- Use rapid-acting insulin analogs (lispro, aspart) 0-15 minutes before meals 1, 2
- Regular insulin can be used 30-45 minutes before meals as alternative 2
Hypoglycemia Management
Treat any glucose <70 mg/dL immediately with 15 grams of fast-acting carbohydrate, recheck in 15 minutes, and repeat if needed. 3
- All patients must carry at least 15g carbohydrate at all times 3
- Scrupulous avoidance of hypoglycemia for 2-3 weeks can reverse hypoglycemia unawareness 2
Renal Impairment Adjustments
For CKD Stage 5, reduce total daily insulin dose by 35-40% in type 1 diabetes. 2, 3