What is the rule for adjusting Lantus (insulin glargine) and sliding scale Lispro (insulin lispro) for a patient with diabetes?

Adjusting Lantus and Sliding Scale Lispro

Sliding scale insulin as monotherapy should be immediately discontinued and replaced with a scheduled basal-bolus regimen, as sliding scale alone is explicitly condemned by all major diabetes guidelines and leads to dangerous glucose fluctuations with only 38% of patients achieving adequate control versus 68% with proper basal-bolus therapy. 1, 2

The Fundamental Problem with Sliding Scale Monotherapy

• Sliding scale insulin treats hyperglycemia after it has already occurred rather than preventing it, resulting in reactive rather than proactive glucose management 1, 2
• This approach leads to rapid glucose fluctuations and treatment failures, with significantly worse outcomes compared to scheduled insulin regimens 2, 3
• All patients requiring insulin should be on a scheduled regimen with basal, prandial, and correction components—not correction insulin alone 1, 2

Proper Insulin Regimen Structure

Basal Insulin (Lantus) Adjustment Algorithm

Initial Dosing:

• Start Lantus at 10 units once daily or 0.1-0.2 units/kg body weight at the same time each day 1
• For severe hyperglycemia (A1C ≥9% or glucose ≥300 mg/dL), consider higher starting doses of 0.3-0.5 units/kg/day as total daily dose 1

Titration Schedule:

• If fasting glucose 140-179 mg/dL: increase Lantus by 2 units every 3 days 1
• If fasting glucose ≥180 mg/dL: increase Lantus by 4 units every 3 days 1
• Target fasting glucose: 80-130 mg/dL 1
• If hypoglycemia occurs: reduce dose by 10-20% immediately 1

Critical Threshold—When to Stop Escalating Basal Insulin:

• When Lantus exceeds 0.5 units/kg/day, adding prandial insulin becomes more appropriate than continuing to escalate basal insulin alone 1
• Clinical signs of "overbasalization" include: basal dose >0.5 units/kg/day, bedtime-to-morning glucose differential ≥50 mg/dL, hypoglycemia episodes, and high glucose variability 1

Prandial Insulin (Lispro) Implementation

When to Add Scheduled Prandial Insulin:

• When basal insulin has been optimized (fasting glucose 80-130 mg/dL) but A1C remains above target after 3-6 months 1
• When basal insulin dose approaches 0.5-1.0 units/kg/day without achieving glycemic targets 1
• When significant postprandial glucose excursions occur (>180 mg/dL) 1

Starting Prandial Insulin:

• Begin with 4 units of lispro before the largest meal OR use 10% of the current basal dose 1
• Administer lispro 0-15 minutes before meals for optimal postprandial control 1, 4
• In hyperglycemic patients, administering lispro 15 minutes before the meal significantly improves postprandial glucose excursion compared to at-meal administration 4

Titration of Prandial Insulin:

• Increase by 1-2 units or 10-15% every 3 days based on 2-hour postprandial glucose readings 1
• Target postprandial glucose: <180 mg/dL 1

Correction Insulin (Lispro) Protocol

Proper Use of Correction Doses:

• Correction insulin should be used as an adjunct to scheduled basal-bolus therapy, never as monotherapy 1, 2
• Use a simplified approach: 2 units lispro for premeal glucose >250 mg/dL and 4 units for premeal glucose >350 mg/dL 1
• Never administer rapid-acting insulin at bedtime to avoid nocturnal hypoglycemia 1

Calculating Individualized Correction Doses:

• Use the insulin sensitivity factor (ISF): ISF = 1500 ÷ Total Daily Dose 1
• Correction dose = (Current glucose - Target glucose) ÷ ISF 1
• Avoid "stacking" correction doses when insulin from the previous dose is still active 1

Complete Basal-Bolus Regimen Example

For a patient requiring insulin intensification:

1. Calculate Total Daily Dose (TDD):

   • Type 2 diabetes: Start with 0.3-0.5 units/kg/day for severe hyperglycemia 1
   • Type 1 diabetes: Typically 0.5 units/kg/day 1

2. Split the TDD:

   • 50% as Lantus (basal) once daily 1, 2
   • 50% as lispro (prandial) divided among three meals 1, 2

3. Add correction doses using the simplified sliding scale as adjunct only 1

Monitoring Requirements

• Daily fasting blood glucose monitoring is essential during titration 1
• Check pre-meal and 2-hour postprandial glucose to guide prandial insulin adjustments 1
• Reassess every 3 days during active titration 1
• Reassess every 3-6 months once stable to evaluate overall glycemic control 1

Critical Pitfalls to Avoid

• Never continue sliding scale insulin as monotherapy—this approach is associated with worse glycemic control and poor clinical outcomes 1, 2, 3
• Never delay adding prandial insulin when basal insulin exceeds 0.5 units/kg/day, as this leads to overbasalization with increased hypoglycemia risk 1
• Never discontinue metformin when starting insulin unless contraindicated, as the combination provides superior control with less weight gain 1
• Never give rapid-acting insulin at bedtime for correction, as this significantly increases nocturnal hypoglycemia risk 1

Special Considerations

For Hospitalized Patients:

• Use a scheduled basal-bolus-plus-correction regimen with 0.4-0.5 units/kg/day total (50% basal, 50% prandial) 2
• For high-risk patients (elderly >65 years, renal failure, poor oral intake), reduce to 0.1-0.25 units/kg/day 1, 2
• Target glucose range: 140-180 mg/dL for most non-critically ill hospitalized patients 2

For Patients on Corticosteroids:

• Increase prandial and correction insulin by 40-60% or more in addition to basal insulin 1, 5
• Consider NPH insulin twice daily to match the glucocorticoid-induced hyperglycemia pattern 5