How do I initiate Mixtard (human insulin) in a patient with steroid-induced hyperglycemia and no prior history of insulin therapy?

Initiating Mixtard in Steroid-Induced Hyperglycemia

For steroid-induced hyperglycemia, start Mixtard 30/70 at 0.3-0.5 units/kg/day given as a single morning dose (at the same time as the steroid), targeting blood glucose 5-10 mmol/L (90-180 mg/dL). 1, 2

Initial Assessment and Dosing

Calculate the starting dose:

• Use 0.3 units/kg/day for elderly patients or those with renal impairment 1, 2
• Use 0.5 units/kg/day for younger patients with normal renal function and higher steroid doses 1, 2
• For a 70 kg patient, this translates to 21-35 units given once in the morning 1

Timing is critical:

• Administer Mixtard at the same time as the morning steroid dose (e.g., if prednisone is given at 8 AM, give Mixtard at 8 AM) 1, 2
• This matches the insulin peak (4-6 hours after injection) with the steroid's peak hyperglycemic effect (6-9 hours after administration) 1, 2

Monitoring Protocol

Implement structured glucose monitoring:

• Check blood glucose four times daily: fasting and 2 hours after each meal 3, 1, 2
• The most important reading is 2 hours after lunch (around 2-3 PM), as this captures the peak steroid effect 1, 2
• Do NOT rely on fasting glucose alone—this will miss the severity of hyperglycemia 1, 2, 4

Target range:

• Aim for 5-10 mmol/L (90-180 mg/dL) throughout the day 3, 2

Dose Titration Algorithm

Adjust doses systematically:

• If afternoon/evening glucose remains above 10 mmol/L, increase Mixtard by 10-15% (or 2-4 units) every 2-3 days 1
• For very high steroid doses (e.g., prednisone >40 mg/day), you may need to increase by 40-60% above the initial dose 2
• Monitor for overnight hypoglycemia as steroids often cause glucose to normalize at night even without treatment 3, 1, 2

Critical Adjustments Based on Steroid Type

For once-daily short-acting steroids (prednisone, methylprednisolone):

• Single morning Mixtard dose is appropriate 3, 1, 2

For long-acting steroids (dexamethasone) or multiple daily doses:

• Mixtard alone is insufficient 1, 2
• Add long-acting basal insulin (glargine or detemir) at 0.2 units/kg/day at bedtime, PLUS continue morning Mixtard at 0.3 units/kg/day 1, 2

For nighttime steroid dosing:

• Switch from Mixtard to long-acting basal insulin (glargine/detemir) given at bedtime instead 2

Common Pitfalls to Avoid

Critical errors that lead to poor outcomes:

• Failing to reduce insulin when steroids are tapered: This is the most common mistake—insulin doses must be decreased proportionally (by the same percentage) as steroid doses decline to prevent hypoglycemia 1, 2, 4

• Using only fasting glucose for monitoring: This misses the peak hyperglycemic effect occurring in the afternoon and evening 1, 2, 4

• Relying on oral agents alone for moderate-to-severe hyperglycemia: If glucose is persistently >15 mmol/L, oral agents are insufficient and insulin is required 3, 2

• Using Mixtard for severe hyperglycemia (glucose >20 mmol/L or "HI" on meter): This requires hospital admission for IV insulin infusion, not subcutaneous Mixtard 3, 4

When Mixtard is NOT Appropriate

Recognize situations requiring alternative approaches:

• Severe hyperglycemia (glucose >20 mmol/L persistently): Requires hospital admission for continuous IV insulin infusion 3, 4

• Long-acting glucocorticoids or continuous steroid use: Requires combination of basal insulin PLUS NPH/Mixtard, as Mixtard alone lacks sufficient basal coverage 3, 1, 2

• Patients requiring maximum flexibility: NPH insulin is preferred over Mixtard because you can independently adjust the basal and prandial components 1, 4

Special Populations

Adjust approach for high-risk patients:

• Elderly or renally impaired: Start at lower end of dosing range (0.2-0.3 units/kg/day) 1, 2

• Patients already on insulin: Add the calculated Mixtard dose (0.3-0.5 units/kg/day) to their existing regimen 2

• Very high steroid doses (>80 mg prednisone equivalent): May require "extraordinary amounts" of insulin—consider early endocrinology consultation 3, 2

Patient Education Essentials

Provide clear instructions:

• Warn patients that glucose levels >20 mmol/L or meter reading "HI" requires immediate hospital presentation for assessment of hyperosmolar hyperglycemic state 3

• Emphasize that insulin doses will need frequent adjustment as steroid doses change 1, 2

• Teach recognition of hypoglycemia symptoms, as overnight hypoglycemia can occur even when daytime glucose is elevated 1, 2