What is the recommended increase in Lantus (insulin glargine) dose for a patient currently receiving 20 units and requiring 4 units per hour on an insulin drip?

Increase Lantus by 48 Units Tomorrow

For a patient requiring 4 units/hour of IV insulin (96 units over 24 hours) while already receiving 20 units of Lantus, the basal insulin dose should be increased to approximately 68 units of Lantus tomorrow. This represents the sum of the current Lantus dose (20 units) plus half of the total IV insulin infused over 24 hours (48 units), following the standard conversion protocol from IV to subcutaneous insulin 1.

Calculation Method

When transitioning from IV to subcutaneous insulin, the total subcutaneous dose equals half of the IV insulin infused over 24 hours 1.

• Current IV insulin requirement: 4 units/hour × 24 hours = 96 units total daily dose
• Conversion to subcutaneous: 96 units ÷ 2 = 48 units
• Patient already receiving: 20 units Lantus
• New Lantus dose: 20 + 48 = 68 units once daily 1

The 50% reduction accounts for the difference in bioavailability and pharmacokinetics between IV and subcutaneous administration 1.

Timing and Administration

• Administer the increased Lantus dose at least 2-3 hours before discontinuing the IV insulin drip to ensure adequate overlap and prevent rebound hyperglycemia 1
• Continue the IV insulin drip for 2-3 hours after giving the subcutaneous Lantus to bridge the gap until the Lantus reaches therapeutic levels 1
• Lantus should be given at the same time each day, typically in the evening 1

Critical Monitoring Requirements

Check point-of-care glucose every 4-6 hours for the first 24-48 hours after transition to identify patterns of hyper- or hypoglycemia 1. Target glucose range for non-critically ill hospitalized patients is 140-180 mg/dL 1.

• If hypoglycemia occurs (glucose <70 mg/dL), immediately reduce the Lantus dose by 10-20% 1
• If fasting glucose remains ≥180 mg/dL after 3 days, increase Lantus by 4 units every 3 days until fasting glucose reaches 80-130 mg/dL 1
• If fasting glucose is 140-179 mg/dL, increase by 2 units every 3 days 1

Adding Correction Insulin

Implement a correction insulin protocol using rapid-acting insulin (aspart or lispro) for premeal glucose >180 mg/dL, separate from the scheduled basal dose 1.

• Glucose 150-200 mg/dL: 2 units rapid-acting insulin 2
• Glucose 201-250 mg/dL: 4 units 2
• Glucose 251-300 mg/dL: 6 units 2
• Glucose 301-350 mg/dL: 8 units 2
• Glucose >350 mg/dL: 10 units and notify provider 2

Common Pitfalls to Avoid

Never discontinue the IV insulin drip simultaneously with giving subcutaneous Lantus, as this creates a dangerous gap in insulin coverage leading to rebound hyperglycemia 1. The 2-3 hour overlap is essential for safe transition.

Never use sliding scale insulin as monotherapy after discontinuing the IV drip 1. Scheduled basal insulin with correction doses as adjunct is the appropriate regimen, as sliding scale alone leads to dangerous glucose fluctuations and is explicitly condemned by all major diabetes guidelines 1.

Do not delay titration if glucose remains elevated 1. Adjust the Lantus dose every 3 days based on fasting glucose patterns rather than waiting weeks for changes.

High-Risk Patient Adjustments

For patients at high risk of hypoglycemia (elderly >65 years, renal impairment with eGFR <45 mL/min/1.73 m², poor oral intake), reduce the calculated dose by 20-30% 1. This would mean starting at approximately 48-54 units instead of 68 units, with more frequent glucose monitoring every 4 hours 1.

For patients with CKD Stage 5, reduce the total daily insulin dose by 50% for type 2 diabetes or 35-40% for type 1 diabetes 1.

Expected Outcomes

With appropriate basal insulin dosing at weight-based calculations, most patients achieve mean blood glucose <140 mg/dL within 3-5 days of transition 1. The goal is fasting glucose 80-130 mg/dL and daytime glucose 140-180 mg/dL for hospitalized patients 1, 2.