What adjustments should be made to the Lantus (insulin glargine) dose, carbohydrate ratio, and correction scale factor for a patient with a fasting blood glucose level of 238 mg/dL, 48 hours after receiving dexamethasone, and currently taking Lantus 30 units, with an ICR of 1:10 and an ISF of 25?

Insulin Dose Adjustments After Dexamethasone-Induced Hyperglycemia

Immediate Lantus Dose Increase

Increase your Lantus from 30 units to 38-40 units immediately, given your fasting blood glucose of 238 mg/dL and persistent overnight hyperglycemia in the 200s following dexamethasone administration 48 hours ago. 1

For fasting glucose ≥180 mg/dL, the evidence-based titration algorithm specifies increasing basal insulin by 4 units every 3 days until fasting glucose reaches 80-130 mg/dL 1. Since you're at 238 mg/dL fasting, an aggressive increase of 8-10 units (approximately 27-33% increase) is warranted to account for dexamethasone-induced insulin resistance 1, 2.

Carbohydrate Ratio Adjustment

Tighten your insulin-to-carbohydrate ratio (ICR) from 1:10 to 1:7 or 1:8 temporarily while dexamethasone effects persist. 1

• Dexamethasone increases insulin resistance by 46-54%, requiring proportionally more prandial insulin to cover the same carbohydrate load 2
• Your current 1:10 ratio means 1 unit covers 10 grams of carbohydrate; changing to 1:7 means 1 unit covers 7 grams, effectively increasing your mealtime insulin by approximately 40% 1
• This adjustment should be maintained for 5-7 days after the last dexamethasone dose, as steroid effects on glucose metabolism persist beyond drug clearance 2

Correction Scale Factor (ISF) Adjustment

Reduce your insulin sensitivity factor from 25 to 15-18 mg/dL per unit. 1

• Your current ISF of 25 means 1 unit of insulin lowers blood glucose by 25 mg/dL 1
• With dexamethasone-induced insulin resistance, you need more insulin to achieve the same glucose reduction 2
• An ISF of 15-18 means each correction unit will lower glucose by 15-18 mg/dL, requiring more units to correct hyperglycemia 1
• Calculate using the formula: 1500 ÷ new total daily dose (TDD) 1

Specific Dosing Algorithm

Basal Insulin (Lantus)

• Day 1-3: Increase to 38-40 units once daily 1
• Day 4-6: If fasting glucose remains >180 mg/dL, increase by another 4 units 1
• Day 7+: Continue titrating by 4 units every 3 days until fasting glucose consistently reaches 80-130 mg/dL 1

Prandial Coverage

• Immediate: Use 1:7 or 1:8 ICR for all meals 1
• Correction doses: Use ISF of 15-18 for pre-meal glucose >130 mg/dL 1
• Target: Pre-meal glucose 90-150 mg/dL, postprandial <180 mg/dL 1

Critical Monitoring Requirements

• Check fasting blood glucose every morning during titration 1
• Check pre-meal and 2-hour postprandial glucose to guide prandial insulin adjustments 1
• Monitor for hypoglycemia as dexamethasone effects wane (typically 5-7 days after last dose) 2
• If any hypoglycemia occurs (glucose <70 mg/dL), reduce the corresponding insulin dose by 10-20% immediately 1

Steroid-Specific Considerations

Dexamethasone causes a 43-53% increase in insulin requirements during hyperglycemic clamp studies, with effects persisting 48-72 hours after the last dose 2. Your blood glucose in the 200s mg/dL 48 hours post-dexamethasone indicates you're still experiencing significant steroid-induced insulin resistance 2.

For patients on steroids requiring higher insulin doses, increase prandial and correction insulin by 40-60% or more in addition to basal insulin adjustments 1. This aligns with your need to adjust both ICR and ISF simultaneously.

When to Revert to Original Settings

• Begin reducing insulin doses back toward baseline 5-7 days after the last dexamethasone dose 2
• Reduce Lantus by 2-4 units every 2-3 days as fasting glucose approaches target 1
• Gradually liberalize ICR back to 1:10 and ISF back to 25 as glucose patterns normalize 1
• Watch closely for hypoglycemia during this transition period 3

Common Pitfalls to Avoid

• Do not delay aggressive insulin intensification when blood glucose levels are persistently in the 200s mg/dL, as this prolongs hyperglycemia exposure and increases complication risk 1
• Do not continue using your original insulin doses during steroid-induced hyperglycemia, as this leads to prolonged uncontrolled glucose levels 1, 2
• Do not forget to reduce insulin doses as steroid effects wane, as failure to do so will cause severe hypoglycemia 3