A patient with labile diabetes on basal insulin glargine (Lantus) 11 U daily and an insulin‑to‑carbohydrate ratio of 1 U per 15 g, who is eating less and has just received dexamethasone 4 mg, how should the basal glargine dose and carb ratio be adjusted?

Insulin Adjustment for Dexamethasone-Induced Hyperglycemia in a Patient with Labile Diabetes

Increase Lantus from 11 units to approximately 16–17 units (≈50% increase) immediately after dexamethasone 4 mg administration, and tighten the carbohydrate ratio from 1:15 to 1:8 for the first 24–48 hours to counteract steroid-induced insulin resistance. 1

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Immediate Basal Insulin (Lantus) Adjustment

• Increase Lantus by approximately 50% (from 11 units to 16–17 units) on the day of dexamethasone administration to counteract the marked insulin resistance induced by the steroid. 1
• Dexamethasone 4 mg causes hyperglycemia that peaks 7–9 hours after administration and persists for at least 24 hours, with the greatest glucose elevations occurring in the afternoon and evening. 1
• At approximately 16 hours post-dose, insulin resistance is near its maximum, affecting both basal and prandial insulin needs. 1
• A standard addition of 0.1–0.3 U/kg/day to the usual regimen is recommended for type 1 diabetes patients on steroids; for a typical adult this equals 8–23 U, making a 5–6 U increase (to 16–17 U) a conservative choice. 1

Tapering Protocol After Steroid Effect Wanes

• At 24 hours post-dose, reduce the basal dose by 10–20% (from 16–17 U to approximately 13–15 U) to prevent hypoglycemia as the steroid effect begins to wane. 1
• At 48 hours post-dose, further reduce to ≈70–75% of the increased dose (12–13 U) to avoid hypoglycemia as steroid effect resolves. 1
• Maintaining the increased insulin dose beyond 24–48 hours markedly raises hypoglycemia risk; ≈75% of inpatient hypoglycemia events are linked to failure to taper basal insulin. 1

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Prandial Insulin & Carbohydrate Ratio Modifications

• Tighten the carbohydrate-to-insulin ratio from 1:15 to 1:8 for the first 24–48 hours, reflecting a ~125% increase in mealtime insulin requirement to match steroid-induced insulin resistance. 1
• Prandial insulin may need a 40–60% increase (or more) during the peak steroid effect, consistent with American Diabetes Association recommendations for steroid-induced hyperglycemia. 1, 2
• After 24 hours, adjust the ratio to ≈1:10–1:12, and return to the baseline 1:15 by 48 hours as insulin resistance resolves. 1

Practical Example for a Patient Eating Minimal Amounts

• If the patient consumes 30 g of carbohydrate at a meal:
  • Baseline ratio (1:15): 30 ÷ 15 = 2 units
  • Steroid-adjusted ratio (1:8): 30 ÷ 8 = 3.75 units (round to 4 units)
• This represents a 2-unit increase per meal during the peak steroid effect. 1

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Correction Scale & Monitoring Protocol

• Implement an intensified correction factor of 1 U per 25 mg/dL above target glucose (versus the usual 1 U per 30–50 mg/dL). 1, 2

Blood Glucose (mg/dL)	Correction Dose (U)
150–175	1
176–200	2
201–250	3
251–300	4
>300	5 + call provider

1, 2

• Check capillary glucose every 4–6 hours for the first 48 hours, emphasizing afternoon/evening readings (4–12 h after dexamethasone). 1, 2
• If fasting glucose at ~24 h remains >180 mg/dL, increase basal insulin by an additional 2–4 U. 1
• Administer correction insulin every 4–6 hours as needed, targeting the afternoon and evening peaks. 1

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Safety Considerations & Critical Pitfalls

• Never discontinue basal insulin in type 1 diabetes, even when glucose appears controlled, to prevent diabetic ketoacidosis (DKA). 1
• If glucose exceeds 300 mg/dL with nausea, vomiting, or abdominal pain, obtain a ketone measurement immediately. 1
• Sliding-scale insulin alone is discouraged by major diabetes guidelines; scheduled basal-bolus adjustments are required for safe glucose control. 1
• Avoid using rapid-acting insulin at bedtime as the sole correction dose, as it increases nocturnal hypoglycemia risk during tapering. 1
• If pre-meal glucose repeatedly exceeds 180 mg/dL despite the tightened ratio, further increase mealtime insulin rather than relying on correction doses. 1
• For persistent hyperglycemia despite basal-bolus adjustments, consider adding a morning dose of NPH insulin (0.1–0.3 U/kg) to provide additional daytime basal coverage. 1, 2

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Expected Clinical Outcomes

• With appropriate basal-bolus modifications for steroid effect, ≈68% of patients achieve mean glucose < 140 mg/dL, versus ≈38% using inadequate sliding-scale regimens. 1
• Total daily insulin requirements may rise 40–60% above baseline during the peak steroid period (24–48 h), often reaching 10–15 U per meal after full titration. 1
• When correctly applied and tapered, basal-bolus therapy does not increase the incidence of hypoglycemia compared with standard care. 1

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Special Considerations for Poor Oral Intake

• Because the patient is "not currently eating much," the carbohydrate ratio adjustment is less critical than the basal insulin increase, as there are fewer carbohydrates to cover. 1
• However, the correction scale remains essential to address steroid-induced hyperglycemia independent of food intake. 1
• If the patient remains NPO or has minimal intake, consider a basal-plus-correction regimen (basal insulin + correction doses only) rather than scheduled prandial insulin. 3, 4
• For patients with poor oral intake, use lower starting doses of 0.1–0.25 units/kg/day for high-risk patients (elderly >65 years, renal failure, poor oral intake). 4

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Summary Algorithm

1. Day 0 (Dexamethasone administration): Increase Lantus from 11 U to 16–17 U. 1
2. Days 0–24 hours: Tighten carb ratio to 1:8 if eating; use correction scale every 4–6 hours. 1, 2
3. 24 hours post-dose: Reduce Lantus by 10–20% (to 13–15 U). 1
4. 24–48 hours: Adjust carb ratio to 1:10–1:12. 1
5. 48 hours post-dose: Reduce Lantus to ≈70–75% of increased dose (12–13 U); return carb ratio to baseline 1:15. 1
6. Monitor closely for hypoglycemia during tapering and adjust doses by 10–20% if glucose < 70 mg/dL. 1