What dose of Humalog 75/25 (insulin lispro protamine/insulin lispro) can a patient take who is currently on 30 units of Lantus (insulin glargine) and 30 units of Humalog (insulin lispro) daily?

Converting from Basal-Bolus to Humalog 75/25

Start with 48 units total daily dose of Humalog 75/25, divided as 32 units before breakfast and 16 units before dinner, representing 80% of the current total daily insulin dose (60 units). 1

Conversion Rationale

The patient's current regimen provides:

• Total daily dose: 60 units (30 units Lantus + 30 units Humalog) 1
• When converting to premixed insulin, guidelines recommend using 80% of the current total insulin dose to reduce hypoglycemia risk during the transition 1
• This yields: 60 units × 0.8 = 48 units total daily dose of Humalog 75/25 1

Dosing Distribution

Split the 48 units as 2/3 before breakfast and 1/3 before dinner: 1

• Morning dose: 32 units (2/3 of 48 units) 1
• Evening dose: 16 units (1/3 of 48 units) 1

This distribution pattern follows the American Diabetes Association's recommended approach for twice-daily premixed insulin regimens 1

Titration Strategy After Initiation

Adjust doses every 2 weeks based on self-monitoring: 2

• Target fasting blood glucose: 90-150 mg/dL 1, 2
• If ≥50% of fasting values exceed goal: increase dose by 2 units 1, 2
• If >2 fasting values/week are <80 mg/dL: decrease dose by 2 units 1, 2

Critical Safety Considerations

Hypoglycemia risk increases substantially with premixed insulin: 2

• The fixed 75/25 ratio (75% insulin lispro protamine, 25% rapid-acting lispro) requires consistent meal timing and carbohydrate content 1, 3
• Patients must eat within 15 minutes of injection to avoid hypoglycemia from the rapid-acting component 3
• Prescribe glucagon for emergent hypoglycemia 1

Important Caveats

This conversion assumes the patient has predictable eating patterns: 1

• Premixed insulin is contraindicated in patients with unpredictable meal schedules because the fixed ratio limits dosing flexibility 1, 2
• If the patient has variable eating habits or requires precise insulin adjustments, maintain the basal-bolus regimen rather than converting to premixed insulin 1, 2

Monitor for overbasalization signals: 1

• If A1C remains above goal despite adequate fasting glucose control, this suggests the premixed insulin ratio is inappropriate 1
• Consider adding a GLP-1 receptor agonist rather than continuing to escalate premixed insulin doses beyond 0.5 units/kg/day 1, 2

Continue metformin if the patient is taking it, but discontinue sulfonylureas and DPP-4 inhibitors to avoid unnecessarily complex regimens and reduce hypoglycemia risk 1, 2