Initiating Mixtard in Steroid-Induced Hyperglycemia
For steroid-induced hyperglycemia, start Mixtard (or preferably NPH insulin alone) at 0.3-0.5 units/kg/day given in the morning to match the peak hyperglycemic effect of glucocorticoids, which occurs 6-9 hours after morning steroid administration. 1, 2
Understanding the Glycemic Pattern
Steroid-induced hyperglycemia has a characteristic diurnal pattern that is critical to understand:
- Peak hyperglycemia occurs 6-9 hours after morning steroid administration, resulting in disproportionate afternoon and evening elevations while overnight glucose often normalizes even without treatment 1, 2
- The degree of hyperglycemia directly correlates with steroid dose—higher doses require more aggressive insulin therapy 1, 2
- Do NOT rely on fasting glucose alone—this will miss the peak hyperglycemic effect and underestimate severity 2, 3
Initial Dosing Strategy
Start with morning NPH insulin rather than premixed Mixtard for better flexibility in dose adjustment:
- Initial dose: 0.3-0.5 units/kg/day given in the morning (simultaneously with the steroid dose) 1, 2
- For patients already on insulin therapy, add NPH at this dose to their existing regimen 2
- For elderly patients or those with renal impairment, start lower at 0.2-0.3 units/kg/day 2
If Using Mixtard Specifically:
- Mixtard 30/70 contains 30% rapid-acting and 70% NPH insulin
- Give the total calculated dose (0.3-0.5 units/kg/day) as a single morning injection before breakfast 1
- The rapid-acting component will cover breakfast while the NPH component matches the steroid's peak effect
Monitoring Requirements
Monitor blood glucose four times daily: fasting and 2 hours after each meal 1, 2, 3
- Target range: 100-180 mg/dL (5.6-10.0 mmol/L) 2, 3
- Most important reading: 2 hours after lunch (around 2-3 PM) as this captures the peak steroid effect 2
- Adjust doses every 2-3 days based on the afternoon/evening glucose pattern 2
Dose Titration Algorithm
Increase NPH/Mixtard by 10-15% (or 2-4 units) every 2-3 days if afternoon/evening glucose remains above target 1
For higher steroid doses (e.g., prednisone ≥40 mg daily or dexamethasone):
- May require 40-60% increase in prandial insulin if patient already on insulin 2
- For extraordinarily high steroid doses, add separate rapid-acting insulin before lunch and dinner in addition to morning NPH 1, 2
Critical Pitfall: Steroid Tapering
As steroids are tapered, insulin doses MUST be proportionally decreased to prevent hypoglycemia—this is the most common error 2, 3
- Reduce insulin by the same percentage as steroid dose reduction 3
- Insulin requirements can decline rapidly after steroid discontinuation 1
- Monitor glucose closely during taper (every 4-6 hours initially) 2
When Mixtard is Insufficient
For patients requiring >0.8-1.0 units/kg/day or with persistent hyperglycemia >250 mg/dL:
- Switch to basal-bolus regimen: NPH in morning + rapid-acting insulin before each meal 1
- Calculate as: 50% basal (NPH), 50% prandial (divided among meals) 1
- For long-acting steroids (dexamethasone) or multiple daily doses, add long-acting basal insulin (glargine/detemir) to control fasting glucose 1, 2
Special Considerations
For once-daily morning prednisone/methylprednisolone:
- Single morning NPH dose is usually sufficient 1, 2
- Patients often reach normal glucose overnight regardless of treatment 1
For dexamethasone or continuous steroid use:
- Requires combination of long-acting basal insulin AND NPH 1, 2
- Start long-acting insulin at 0.2 units/kg/day at bedtime, plus morning NPH at 0.3 units/kg/day 1
Avoid these common errors:
- Using only sliding-scale correction insulin without scheduled basal insulin—this leads to poor control 2, 3
- Relying solely on oral antidiabetic agents for high-dose steroid therapy—these are insufficient 2, 3
- Monitoring only fasting glucose—this misses the critical afternoon hyperglycemia 2, 3
When to Escalate Care
Consult endocrinology if: