What is the appropriate initial insulin glargine dose for a 24‑year‑old woman with type 1 diabetes mellitus who weighs 60.2 kg?

Initial Insulin Glargine Dosing for Type 1 Diabetes

For a 24-year-old woman with type 1 diabetes weighing 60.2 kg, start with a total daily insulin dose of 30 units (0.5 units/kg/day), giving 15 units of insulin glargine once daily as basal insulin and 15 units of rapid-acting insulin divided among meals (approximately 5 units per meal). 1, 2

Calculating the Starting Dose

Total Daily Insulin Requirement

• The standard starting dose for metabolically stable type 1 diabetes patients is 0.5 units/kg/day 1, 2
• For a 60.2 kg patient: 0.5 × 60.2 = 30.1 units total daily dose 1, 2
• The acceptable range is 0.4–1.0 units/kg/day (24–60 units/day for this patient) 1, 2

Basal vs. Prandial Split

• Basal insulin (glargine) should comprise 40–50% of the total daily dose, equating to 12–15 units once daily 1, 2
• Prandial insulin (rapid-acting) should comprise 50–60% of the total daily dose, equating to 15–18 units total, divided across three meals (approximately 5–6 units per meal) 1, 2
• Administer glargine at the same time each day (typically bedtime) 3
• Give rapid-acting insulin 0–15 minutes before each meal 1, 2

Titration Protocol

Basal Insulin Adjustment

• Increase glargine by 2 units every 3 days if fasting glucose is 140–179 mg/dL 2
• Increase glargine by 4 units every 3 days if fasting glucose is ≥180 mg/dL 2
• Target fasting glucose: 80–130 mg/dL 2
• If hypoglycemia occurs, reduce the dose by 10–20% immediately 2

Prandial Insulin Adjustment

• Adjust each meal dose by 1–2 units (or 10–15%) every 3 days based on 2-hour postprandial glucose 2
• Target postprandial glucose: <180 mg/dL 2

Critical Monitoring Requirements

• Check fasting blood glucose every morning during titration 2
• Monitor pre-meal and 2-hour postprandial glucose to guide prandial adjustments 2
• Reassess every 3 months with HbA1c monitoring 2
• Daily self-monitoring of blood glucose is essential during the titration phase 2

Special Considerations for This Patient

Higher Doses May Be Needed If:

• The patient presents with diabetic ketoacidosis: start with 0.6–1.0 units/kg/day before subsequent titration 2
• The patient is in puberty: higher doses are often required 1
• The patient has acute illness or infection 1

Lower Doses May Be Appropriate If:

• The patient is in the "honeymoon phase" with residual beta-cell function: may require only 0.2–0.6 units/kg/day 2

Administration Guidelines

• Administer glargine subcutaneously into the abdominal area, thigh, or deltoid 3
• Rotate injection sites within the same region to prevent lipodystrophy 3
• Do not mix glargine with any other insulin due to its low pH 3
• Do not administer intravenously or via an insulin pump 3
• Glargine must be used concomitantly with short-acting insulin in type 1 diabetes 3

Critical Pitfalls to Avoid

• Never use sliding-scale insulin as monotherapy in type 1 diabetes—this can precipitate diabetic ketoacidosis 2
• Never administer rapid-acting insulin at bedtime as a sole correction dose—this markedly raises nocturnal hypoglycemia risk 2
• Never delay insulin initiation or prescribe inadequate doses—immediate basal-bolus therapy is required for type 1 diabetes 2
• Do not continue escalating basal insulin beyond 0.5–1.0 units/kg/day without addressing postprandial hyperglycemia 2

Expected Outcomes

• With appropriate basal-bolus therapy, patients can achieve HbA1c reduction of 1–2% over 3–6 months 4
• Glargine demonstrates lower frequency of nocturnal hypoglycemia compared to NPH insulin (6.56 vs. 9.0 episodes/patient-month) 5
• The once-daily glargine regimen provides more stable glucose control with improved treatment satisfaction compared to NPH insulin 5, 4