What should the Lantus (glargine) dose be for a patient with insulin-dependent diabetes, currently receiving 4 units/hour of insulin via drip and D5 (dextrose 5%) at 100ml/hr, once the D5 is stopped?

Transitioning from Insulin Drip to Lantus: Calculating the Basal Dose

Immediate Calculation and Administration

For a patient requiring 4 units/hour of IV insulin, start with 48 units of Lantus once daily, calculated as 50% of the total 24-hour IV insulin requirement (4 units/hour × 24 hours = 96 units; 50% = 48 units), and administer this dose 1-2 hours BEFORE discontinuing the insulin drip to prevent rebound hyperglycemia. 1

Critical Timing Protocol

• The first dose of Lantus must be given 1-2 hours before stopping the IV insulin drip to ensure adequate overlap, as IV insulin has a very short plasma half-life and discontinuation without prior subcutaneous coverage will cause rapid metabolic decompensation 1
• Never discontinue IV insulin without prior subcutaneous dosing, especially in insulin-dependent patients, as this precipitates dangerous hyperglycemia 1

Accounting for Nutritional Status

The D5 infusion at 100 mL/hr provides continuous carbohydrate load (approximately 120 grams/24 hours) that requires BOTH basal AND nutritional insulin coverage—the 48 units of Lantus addresses only the basal component. 1

When D5 Continues After Transition

• If D5 continues running, add nutritional insulin coverage using either regular insulin every 6 hours OR rapid-acting insulin every 4 hours, calculated at approximately 1 unit per 10-15 grams of carbohydrate in the dextrose solution 1
• The basal insulin dose (48 units Lantus) remains unchanged regardless of nutritional status, but additional scheduled nutritional insulin is required for ongoing dextrose infusion 1

When D5 is Stopped

• If D5 is discontinued and the patient is NPO (nothing by mouth), the 48 units of Lantus provides adequate basal coverage alone 1
• However, if the patient begins eating after D5 is stopped, prandial insulin must be added—start with 4 units of rapid-acting insulin before the largest meal or 10% of the basal dose 2

Risk-Based Dose Adjustments

Reduce the calculated 48-unit dose by 20-50% in high-risk populations to prevent severe hypoglycemia. 1

High-Risk Patient Categories

• Elderly patients (>65 years): Use 0.1-0.25 units/kg/day instead of standard dosing 2, 1
• Patients with renal impairment: For CKD Stage 5, reduce total daily insulin by 50% for type 2 diabetes or 35-40% for type 1 diabetes 2, 1
• Patients with poor oral intake: Reduce dose by 20-50% and monitor glucose every 4-6 hours 1

Post-Transition Monitoring and Titration

Immediate Monitoring Requirements

• Check point-of-care glucose every 4-6 hours initially after transition, with more frequent monitoring if the patient was previously unstable on the drip 1
• Daily fasting blood glucose monitoring is essential during the titration phase 2

Evidence-Based Titration Algorithm

• Increase Lantus by 2 units every 3 days if fasting glucose is 140-179 mg/dL 2, 1
• Increase Lantus by 4 units every 3 days if fasting glucose is ≥180 mg/dL 2, 1
• Target fasting plasma glucose: 80-130 mg/dL 2
• If hypoglycemia occurs without clear cause, reduce dose by 10-20% immediately 2

Critical Threshold: Recognizing When Basal Insulin Alone Is Insufficient

When the Lantus dose exceeds 0.5 units/kg/day (approximately 35-40 units for a 70 kg patient) and glucose remains elevated, this signals the need for prandial insulin coverage rather than further basal insulin escalation. 2, 1

Signs of Overbasalization

• Basal insulin dose >0.5 units/kg/day 2
• Bedtime-to-morning glucose differential ≥50 mg/dL 2
• Episodes of hypoglycemia with persistent hyperglycemia at other times 2
• High glucose variability throughout the day 2

Common Pitfalls to Avoid

• Never use sliding scale insulin alone during the transition—this approach treats hyperglycemia reactively rather than preventing it, leading to dangerous glucose fluctuations 1
• Do not forget nutritional insulin coverage if the patient continues receiving dextrose or begins eating, as continuous carbohydrate load requires scheduled insulin beyond basal coverage 1
• Do not continue escalating basal insulin beyond 0.5-1.0 units/kg/day without addressing postprandial hyperglycemia, as this leads to overbasalization with increased hypoglycemia risk 2, 1