What should be the adjusted morning and evening Lantus (insulin glargine) doses and carb ratio for a patient with hyperglycemia, currently on 100 units of Lantus in the morning and 25 units in the evening, taking 15-35 units of insulin with each meal, who will be starting dexamethasone 4 mg?

Insulin Adjustment for Dexamethasone-Induced Hyperglycemia

Morning Lantus Dose

Increase morning Lantus from 100 units to 150-160 units (50-60% increase) for the duration of dexamethasone therapy. 1, 2

• Dexamethasone 4 mg causes peak hyperglycemia 7-9 hours after administration, corresponding to late morning and afternoon elevations, requiring substantial increases in basal insulin coverage 3, 1
• For patients already on insulin receiving glucocorticoids, adding 0.3-0.4 units/kg/day to the usual insulin regimen significantly improves glycemic control 1, 2
• The morning dose bears the primary burden of dexamethasone-induced insulin resistance, as the steroid effect peaks during daytime hours and persists for at least 24 hours 3, 1
• Guidelines recommend insulin requirements typically increase by 0.3-0.4 units/kg/day with dexamethasone-induced hyperglycemia, distributed primarily to basal coverage 2

Evening Lantus Dose

Increase evening Lantus from 25 units to 40-45 units (60-80% increase) to cover overnight and early morning insulin resistance. 1, 2

• Dexamethasone's prolonged action means insulin resistance continues into the next day, requiring sustained basal insulin coverage through the night 3, 1
• The evening dose must prevent fasting hyperglycemia that results from persistent glucocorticoid effects on hepatic glucose production 3
• For hospitalized patients with glucocorticoid use, basal insulin represents 25-30% of total daily insulin requirements, but this proportion increases substantially with dexamethasone 2

Carbohydrate Ratio Adjustment

Tighten carb ratio from current 1:8-1:10 range to 1:5-1:6 (representing a 40-50% increase in mealtime insulin) for meals during peak steroid effect. 1

• Dexamethasone causes peak hyperglycemia 7-9 hours after administration, meaning lunch and dinner require the most aggressive prandial coverage 3, 1
• Adjusting the carbohydrate ratio from 1:8 to approximately 1:6 (representing a 30% increase in mealtime insulin) for 24-48 hours after dexamethasone administration helps counteract steroid-induced insulin resistance 1
• Prandial and correction insulin should be increased by 40-60% or more in addition to basal insulin for patients on steroids requiring higher insulin doses 4
• The current 15-35 unit range per meal suggests highly variable carbohydrate intake; standardizing to 1:5-1:6 ratio provides more predictable coverage during steroid therapy 1

Correction Scale Intensification

Implement an aggressive correction scale using a correction factor of 1:20-1:25 (compared to baseline 1:30-1:40) administered every 4-6 hours. 1

• Implementing a more aggressive correction scale with rapid-acting insulin every 4-6 hours, using a correction factor calculated as 1500 divided by the new total daily insulin dose, is recommended 1
• For patients with high BMI and insulin resistance, the 150% dose increase may be insufficient, and consideration of increasing to 200% of baseline may be necessary 1
• Blood glucose 180-220 mg/dL: 4 units rapid-acting insulin 2
• Blood glucose 221-260 mg/dL: 6 units rapid-acting insulin 2
• Blood glucose 261-300 mg/dL: 8 units rapid-acting insulin 2
• Blood glucose >300 mg/dL: 10 units rapid-acting insulin and notify physician 2

Critical Monitoring Requirements

Check blood glucose before each meal and at bedtime (minimum 4 times daily), with particular attention to afternoon and evening readings when dexamethasone-induced hyperglycemia peaks. 3, 1, 2

• Monitoring blood glucose every 4-6 hours during the steroid effect period, focusing on afternoon and evening readings when dexamethasone-induced hyperglycemia peaks, is crucial 1
• Target blood glucose 140-180 mg/dL during dexamethasone therapy, accepting slightly higher targets than usual given the difficulty of achieving tight control with glucocorticoids 2
• Reassess insulin doses daily while on dexamethasone, as requirements can change rapidly 2

Tapering Strategy After Dexamethasone Discontinuation

Reduce all insulin doses by 30-40% immediately when dexamethasone is stopped, then decrease by an additional 10-20% every 1-2 days while monitoring closely for hypoglycemia. 1, 2

• Insulin requirements can decline rapidly after dexamethasone is stopped, and doses must be adjusted accordingly to prevent hypoglycemia 1
• Beginning to reduce Lantus dose back toward baseline once fasting blood glucose consistently falls below 180 mg/dL, decreasing by 10-20% every 1-2 days while monitoring closely for hypoglycemia, is advised 1
• The transition from 24 to 48 hours post-dexamethasone is a high-risk period for hypoglycemia if insulin doses are not appropriately reduced 1
• Insulin requirements can decline rapidly after dexamethasone is stopped; reduce insulin doses by 20-30% immediately when steroids are discontinued 2

Common Pitfalls to Avoid

The most dangerous error is maintaining the increased insulin doses beyond 24-48 hours after dexamethasone discontinuation, as this creates severe hypoglycemia risk when steroid effects dissipate. 1

• The most dangerous error is maintaining the increased insulin doses beyond 24-48 hours, as this creates severe hypoglycemia risk when steroid effects dissipate 1
• Avoid using sulfonylureas during steroid therapy as they increase hypoglycemia risk and provide inadequate coverage for steroid-induced hyperglycemia 1
• Do not rely solely on correction insulin; scheduled basal-bolus regimens are superior to sliding scale monotherapy for steroid-induced hyperglycemia 4, 5
• Basal and bolus insulin regimen is an effective and safe approach for managing dexamethasone-induced hyperglycemia, with studies showing average blood glucose of 219 mg/dL with basal-bolus versus 301 mg/dL with sliding scale alone 5

Special Considerations for This Patient

This patient's high baseline insulin requirements (125 units basal + 45-105 units prandial daily) indicate significant insulin resistance, likely requiring doses at the higher end of recommended increases. 1, 2

• For patients with high BMI and insulin resistance, the 150% dose increase may be insufficient, and consideration of increasing to 200% of baseline may be necessary 1
• The degree of hyperglycemia correlates with the dose of steroid, and adjustments to steroid doses frequently necessitate adjustment of the associated diabetes treatment regimen 3
• Dexamethasone causes hyperglycemia through impaired beta-cell insulin secretion, increased insulin resistance, and enhanced hepatic gluconeogenesis, with effects persisting for at least 24 hours after administration 1