In a patient with type 1 diabetes on insulin glargine (Lantus) 11 U daily and an insulin‑to‑carbohydrate ratio of 1 U per 15 g carbs who received a single 4 mg dose of dexamethasone, how much should the basal insulin be increased and how should the carbohydrate ratio be adjusted?

Insulin Adjustment After Single-Dose Dexamethasone 4 mg

Immediate Basal Insulin Increase (First 24–48 Hours)

Increase Lantus from 11 units to approximately 16–17 units (≈50% increase) for the next 24–48 hours to counter dexamethasone-induced insulin resistance. 1, 2

• Dexamethasone 4 mg causes hyperglycemia that peaks 7–9 hours after administration and persists for at least 24 hours, with effects substantially diminishing by 48 hours. 2
• High-dose glucocorticoids typically require 40–60% or more additional insulin beyond baseline requirements. 3
• For a patient on 11 units Lantus (approximately 0.16 units/kg for a typical 68 kg adult), a 50% increase to 16–17 units provides adequate coverage during peak steroid effect. 1, 2
• Administer the increased Lantus dose at the usual bedtime to ensure continuous 24-hour basal coverage during the steroid-induced insulin-resistant period. 1

Carbohydrate Ratio Tightening (First 24–48 Hours)

Tighten the carbohydrate ratio from 1:15 to approximately 1:10 (≈50% increase in prandial insulin) for meals during the first 24–48 hours. 1, 2

• Dexamethasone causes pronounced afternoon-and-evening hyperglycemia through impaired beta-cell insulin secretion, increased insulin resistance, and enhanced hepatic gluconeogenesis. 1
• A 1:10 ratio (1 unit per 10 g carbohydrate) represents a 50% increase in mealtime insulin coverage, matching the magnitude of steroid-induced insulin resistance. 1, 2
• This adjustment should be applied to all three meals, as dexamethasone affects both fasting and postprandial glucose. 1

Correction Insulin Protocol

Implement an intensified correction scale using rapid-acting insulin every 4–6 hours when glucose exceeds 150 mg/dL. 1, 2

Glucose (mg/dL)	Correction Dose (units)
150–200	2
201–250	4
251–300	6
>300	8 + notify provider

1

• Calculate the insulin sensitivity factor as 1500 ÷ total daily insulin dose to individualize corrections. 3
• Correction doses must supplement—not replace—scheduled basal and prandial insulin. 3

Monitoring Requirements (First 48 Hours)

Check blood glucose every 4–6 hours for the first 48 hours after dexamethasone administration, with particular attention to afternoon, evening, and overnight values. 1, 2

• Dexamethasone-induced hyperglycemia peaks in the afternoon and evening (7–9 hours post-dose) and continues into the next day. 2
• Target daytime glucose 140–180 mg/dL and fasting glucose <130 mg/dL during the steroid effect period. 1, 2
• The transition from 24 to 48 hours post-dexamethasone is a high-risk period for hypoglycemia if insulin doses are not appropriately reduced. 2

Dose Reduction at 48 Hours Post-Dexamethasone

At 48 hours, reduce Lantus from 16–17 units back to approximately 13–14 units (≈50–65% of the increased dose) as steroid effects wane. 2

• Insulin requirements decline rapidly after dexamethasone is stopped, and doses must be adjusted accordingly to prevent hypoglycemia. 2
• Maintaining the increased dose of 16–17 units at 48 hours creates substantial hypoglycemia risk. 2
• Return the carbohydrate ratio from 1:10 to approximately 1:12 or 1:13 (representing a 30–40% reduction in mealtime insulin from the peak steroid period) to prevent hypoglycemia as insulin resistance normalizes. 2

Algorithmic Approach to 48-Hour Dose Titration

• If blood glucose remains >180 mg/dL at 48 hours: maintain Lantus at 16–17 units and reassess in 12 hours. 2
• If blood glucose is 100–140 mg/dL at 48 hours: reduce Lantus to 13–14 units (approximately 50–60% of increased dose). 2
• If blood glucose is <100 mg/dL at 48 hours: reduce Lantus to 11–12 units (baseline or slightly above) and monitor closely for hypoglycemia. 2

Return to Baseline (72 Hours and Beyond)

By 72 hours post-dexamethasone, return Lantus to baseline 11 units and carbohydrate ratio to 1:15, provided blood glucose values have normalized. 2

• Some residual steroid effect may persist beyond 48 hours with dexamethasone (a long-acting glucocorticoid), requiring continued monitoring for 72 hours. 2
• If fasting blood glucose consistently falls below 100 mg/dL before 72 hours, accelerate the return to baseline dosing. 2

Critical Safety Considerations

The most dangerous error is maintaining increased insulin doses beyond 24–48 hours, as this creates severe hypoglycemia risk when steroid effects dissipate. 2

• Check blood glucose every 4–6 hours for the next 24 hours after the 48-hour dose reduction, with particular attention to overnight and fasting values when hypoglycemia risk is highest. 2
• If any glucose reading falls <70 mg/dL, reduce the corresponding insulin dose by 10–20% immediately without waiting for further data. 3, 2
• Treat hypoglycemia with 15 g of fast-acting carbohydrate, recheck in 15 minutes, and repeat if needed. 3

Special Considerations for This Patient

• With a baseline Lantus dose of 11 units and a 1:15 carbohydrate ratio, this patient likely has relatively good insulin sensitivity and lower baseline insulin requirements. 3
• The 50% dose increase (to 16–17 units) may be conservative; if glucose remains >250 mg/dL despite this adjustment, consider increasing to 18–20 units (≈80% increase). 1
• A single 4 mg dose of dexamethasone produces less profound hyperglycemia than higher doses (e.g., 40 mg), but the same principles of aggressive initial dosing followed by rapid tapering apply. 1, 4, 5

Alternative Approach: Basal-Bolus Intensification

If the above adjustments fail to achieve target glucose <180 mg/dL, consider adding scheduled rapid-acting insulin before meals rather than relying solely on correction doses. 4

• Start with 4 units of rapid-acting insulin before each of the three largest meals in addition to the increased Lantus dose. 3
• A basal-bolus insulin regimen with detemir and aspart is superior to sliding-scale regular insulin for management of dexamethasone-induced hyperglycemia, achieving mean blood glucose of 219 mg/dL versus 301 mg/dL. 4
• This approach is particularly important if the patient receives repeated doses of dexamethasone or higher doses (>4 mg). 4

Common Pitfalls to Avoid

• Do not delay aggressive insulin dosing when glucose exceeds 250 mg/dL; an upfront increase is required rather than gradual titration. 1
• Avoid using the same Lantus dose employed for routine diabetes management; steroid-induced insulin resistance necessitates a substantially higher dose. 1
• Do not use sulfonylureas during this transition period as they increase hypoglycemia risk. 2
• Never rely solely on correction insulin without adjusting scheduled basal and prandial doses; this reactive strategy is condemned by major diabetes guidelines. 3