What is the appropriate starting dose of Lantus (insulin glargine) for a patient weighing 110 pounds with an A1C greater than 14% and taking metformin 500mg daily?

Lantus Dosing for 110-Pound Patient with A1C >14% on Metformin 500mg Daily

Start Lantus at 10 units once daily at bedtime, and increase the dose by 4 units every 3 days until fasting blood glucose reaches 80-130 mg/dL. 1

Initial Dose Calculation

For this 110-pound (50 kg) patient with severe hyperglycemia (A1C >14%), the recommended starting dose is 10 units once daily 1, 2. This aligns with the FDA-approved dosing for insulin-naive type 2 diabetes patients of 0.2 units/kg or up to 10 units once daily 2. For a 50 kg patient, 0.2 units/kg would equal exactly 10 units 1.

Aggressive Titration Protocol Required

Given the extreme hyperglycemia (A1C >14%), this patient requires aggressive titration 1:

• Increase by 4 units every 3 days if fasting glucose ≥180 mg/dL 1
• Increase by 2 units every 3 days if fasting glucose is 140-179 mg/dL 1
• Continue titration until fasting plasma glucose reaches 80-130 mg/dL 1

The American Diabetes Association explicitly recommends this aggressive 4-unit increment for patients with severe hyperglycemia 1. At this A1C level, more conservative titration would unnecessarily prolong exposure to dangerous hyperglycemia 1.

Critical Threshold: When to Add Prandial Insulin

Do not continue escalating Lantus beyond 0.5 units/kg/day (25 units for this patient) without adding prandial insulin. 1, 3 When basal insulin exceeds this threshold and glucose remains elevated, adding rapid-acting insulin before meals becomes more appropriate than continuing to increase basal insulin alone 1.

Clinical signals that you've reached this threshold include 1:

• Basal dose >0.5 units/kg/day (>25 units for this 50 kg patient)
• Bedtime-to-morning glucose differential ≥50 mg/dL
• Hypoglycemia episodes
• High glucose variability

For patients with A1C >10%, basal-bolus insulin from the outset may be more appropriate than basal insulin alone 1. Consider starting with 4 units of rapid-acting insulin before the largest meal once basal insulin is optimized 1.

Optimize Metformin Dosing

Increase metformin to at least 1000mg twice daily (2000mg total) unless contraindicated. 4 The current dose of 500mg daily is subtherapeutic. The American Diabetes Association recommends advancing to 850mg or two 500mg tablets twice daily after 5-7 days if gastrointestinal side effects have not occurred 4. Metformin should be continued when adding or intensifying insulin therapy, as it reduces total insulin requirements and provides complementary glucose-lowering effects 1, 3.

Maximum effective metformin dose is up to 2500mg/day, though 1700-2000mg daily is often sufficient 4. For this patient with severe hyperglycemia, aim for at least 2000mg daily in divided doses 5.

Monitoring Requirements

• Daily fasting blood glucose monitoring is essential during titration 1
• Check A1C every 3 months during intensive titration 1
• Assess for hypoglycemia at every visit 1
• If hypoglycemia occurs, reduce dose by 10-20% immediately 1

Common Pitfalls to Avoid

Do not delay insulin intensification. 1 At A1C >14%, prolonged severe hyperglycemia increases complication risk and should be corrected rapidly 1.

Do not rely on sliding scale insulin alone. 1 Scheduled basal insulin with systematic titration is required for effective glycemic management 1.

Do not continue escalating basal insulin beyond 0.5-1.0 units/kg/day without addressing postprandial hyperglycemia. 1, 3 This leads to "overbasalization" with increased hypoglycemia risk and suboptimal control 1.

Do not add or continue sulfonylureas when intensifying insulin. 6 The combination significantly increases hypoglycemia risk without substantial additional benefit 6, 7.

Expected Outcomes

With proper titration, expect the final Lantus dose to be approximately 0.44-0.46 units/kg (22-23 units for this patient) if using basal insulin alone 7, 8. However, given the extreme A1C elevation, this patient will likely require prandial insulin coverage in addition to basal insulin to achieve adequate control 1.

Patients on metformin alone (without sulfonylureas) achieve greater A1C reductions, less weight gain, and lower hypoglycemia rates during insulin titration 3. This patient's current regimen of metformin only (once optimized to therapeutic doses) positions them well for successful insulin initiation 3.