What should the Lantus (insulin glargine) dose and carb ratio be for a patient taking 12 units and 1:7 carb ratio after receiving dexamethasone 4 mg?

Insulin Adjustment After Dexamethasone 4 mg

Increase your Lantus dose to 18 units today (150% of baseline) and tighten your carb ratio to 1:5 for the next 24-48 hours. 1, 2

Lantus (Basal Insulin) Adjustment

For today and tomorrow, use 18 units of Lantus (an increase from your baseline 12 units to 150% of baseline dose). 1, 2

• Dexamethasone causes significant afternoon and evening hyperglycemia that persists for at least 24 hours after administration, driven by impaired beta cell function, increased insulin resistance, and enhanced hepatic glucose production. 2, 3
• The 4 mg dose you received yesterday will peak 7-9 hours after administration and continue affecting your glucose control through today and into tomorrow. 3
• Maintain this higher 18-unit dose for at least 24 hours after the dexamethasone was given (so through today at minimum), then gradually taper back to your baseline 12 units while monitoring glucose levels closely. 2, 3

Carbohydrate Ratio Adjustment

Change your carb ratio from 1:7 to 1:5 for the next 24-48 hours (meaning you'll need 1 unit of rapid-acting insulin for every 5 grams of carbohydrate instead of every 7 grams). 1, 3

• This represents approximately a 40% increase in mealtime insulin to counteract the steroid-induced insulin resistance. 1, 3
• The American Diabetes Association recommends adjusting carb ratios to 1:7 or 1:8 for high-dose glucocorticoids, but since you're already at 1:7 baseline, a more aggressive adjustment to 1:5 is warranted. 1
• Return gradually to your baseline 1:7 ratio as the dexamethasone effects diminish over the next 48 hours. 3

Monitoring Strategy

Check your blood glucose every 4-6 hours today and tomorrow, with particular attention to afternoon and evening readings (when steroid effects are most pronounced). 2, 3

• Use a more aggressive correction scale: add 1 unit of rapid-acting insulin for every 25 mg/dL above your target glucose. 1
• If glucose remains elevated despite these adjustments, consider adding NPH insulin in the morning (0.1-0.3 units/kg) in addition to your Lantus. 1

Critical Safety Considerations

Watch for hypoglycemia as dexamethasone effects wane - approximately 48 hours after the dose, you may need to reduce insulin doses quickly to avoid dangerous lows. 1, 2

• The hyperglycemic effect is most pronounced 7-9 hours post-dose but can persist beyond 24 hours. 3
• Early and aggressive insulin adjustment prevents significant hyperglycemia and potential complications like diabetic ketoacidosis, which has been documented in patients receiving dexamethasone with inadequate insulin coverage. 4
• Do not restrict carbohydrate intake to manage the hyperglycemia - instead optimize insulin therapy to avoid malnutrition risk. 1