After receiving 6 mg dexamethasone 24 hours ago (none today), a patient on a 1 U/6 g carbohydrate‑to‑insulin ratio with 22 U NPH (Neutral Protamine Hagedorn) insulin and a high correction factor asks: what carbohydrate‑to‑insulin ratio and correction factor should be used now?

Insulin Adjustment 48 Hours After Dexamethasone Discontinuation

Reduce Lantus to approximately 14–16 units (50–60% of the current 28-unit dose) and return the carbohydrate ratio to 1:8 or 1:10, while implementing a standard correction scale instead of the high-dose protocol. 1, 2

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Understanding the 48-Hour Time Point

• Dexamethasone's hyperglycemic effect peaks 7–9 hours after administration and persists for at least 24 hours, but effects substantially diminish by 48 hours after the last dose. 1
• The steroid-induced insulin resistance decreases rapidly once the glucocorticoid effect wanes, creating a critical window where maintaining elevated insulin doses leads to severe hypoglycemia. 2, 3
• The 24–48 hour transition period represents the highest risk for hypoglycemia if insulin doses are not appropriately reduced. 2

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Specific Lantus Dose Adjustment at 48 Hours

• Decrease Lantus from 28 units to 14–16 units (approximately 50–60% of the increased dose), as you are now beyond the peak steroid effect. 2
• Maintaining the current 28-unit dose at 48 hours creates substantial hypoglycemia risk because insulin sensitivity is returning to baseline while insulin levels remain elevated. 2
• If fasting glucose remains >180 mg/dL at 48 hours, maintain Lantus at 28 units and reassess in 12 hours; if fasting glucose is 100–140 mg/dL, reduce to 14–16 units immediately. 2

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Carbohydrate Ratio Modification

• Return the carb ratio from 1:6 to approximately 1:8 or 1:10, representing a 30–40% reduction in mealtime insulin from the peak steroid period. 2
• This adjustment prevents hypoglycemia as insulin resistance normalizes and the exaggerated insulin requirements of the steroid period resolve. 2
• Monitor pre-meal and 2-hour post-meal glucose levels to fine-tune this ratio over the next 24 hours, as individual responses vary. 2

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Correction Scale Adjustment

• Switch from the "high correction scale" to a standard correction scale immediately, as insulin sensitivity is returning to baseline. 2
• Use correction insulin every 4–6 hours as needed, but expect significantly less need for corrections compared to the first 24 hours after dexamethasone. 2
• The standard correction scale typically uses 2 units for glucose >250 mg/dL and 4 units for glucose >350 mg/dL, rather than the more aggressive dosing used during active steroid effect. 4

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Critical Monitoring Requirements

• Check blood glucose every 4–6 hours for the next 24 hours, with particular attention to overnight and fasting values when hypoglycemia risk is highest. 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
• Continue monitoring for 72 hours total, as dexamethasone is a long-acting glucocorticoid and some residual effect may persist beyond 48 hours. 2

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Algorithmic Approach to Dose Titration

If Blood Glucose >180 mg/dL at 48 Hours:

• Maintain current Lantus at 28 units and reassess in 12 hours. 2
• Continue the 1:6 carb ratio for one more meal cycle before adjusting. 2

If Blood Glucose 100–140 mg/dL at 48 Hours:

• Reduce Lantus to 14–16 units (50–60% of current dose) immediately. 2
• Return carb ratio to 1:8 or 1:10. 2
• Switch to standard correction scale. 2

If Blood Glucose <100 mg/dL at 48 Hours:

• Reduce Lantus to 12–14 units (approximately 40–50% of current dose). 2
• Return carb ratio to 1:10. 2
• Hold correction insulin unless glucose exceeds 250 mg/dL. 2

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Physiologic Rationale

• Dexamethasone causes hyperglycemia through three mechanisms: impaired beta-cell insulin secretion, increased total body insulin resistance, and enhanced hepatic gluconeogenesis. 1, 5
• These effects are time-limited, with maximal impact at 24 hours and substantial resolution by 48 hours. 6
• Studies show that a single 8-mg dose of dexamethasone increases blood glucose, insulin, and C-peptide levels maximally at 24 hours, with levels returning toward baseline at 48 hours. 6
• Dexamethasone decreases glucose oxidation and whole body glucose uptake independently of increased lipolysis or altered muscle blood flow, but these effects reverse as the drug is cleared. 5

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Common Pitfalls to Avoid

• The most dangerous error is maintaining the increased insulin doses beyond 24–48 hours, as this creates severe hypoglycemia risk when steroid effects dissipate. 2
• Do not wait for multiple episodes of hypoglycemia before reducing insulin; proactive dose reduction at 48 hours is essential. 2
• Avoid using sulfonylureas during this transition period, as they increase hypoglycemia risk when combined with declining steroid effect. 2
• Do not assume a linear taper is appropriate; the steroid effect diminishes more rapidly than a gradual reduction would suggest. 1, 2

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Special Considerations for Dexamethasone

• Dexamethasone is a long-acting glucocorticoid requiring different management than intermediate-acting steroids like prednisone, affecting both fasting and postprandial glucose. 2
• The prolonged action means some residual effect may persist beyond 48 hours, requiring continued monitoring for 72 hours total. 2
• For patients with high BMI (>40) and significant insulin resistance, the standard 50–60% reduction may need to be modified to 60–70% of the increased dose. 1

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Expected Clinical Outcomes

• With appropriate dose reduction at 48 hours, fasting glucose should stabilize in the 80–130 mg/dL range within 3–7 days. 2
• Post-prandial glucose should return to <180 mg/dL with the adjusted carb ratio. 2
• The need for correction insulin should decrease dramatically compared to the first 24–48 hours. 2
• By 72 hours, most patients can return to their pre-dexamethasone insulin regimen if glucose remains stable. 2