Transitioning from Humalog Mix 75-25 to Novolog Mix 70-30
When transitioning from Humalog Mix 75-25 to Novolog Mix 70-30, use a 1:1 unit-for-unit conversion and maintain the same twice-daily dosing schedule (before breakfast and dinner), with close glucose monitoring for the first 1-2 weeks to identify any need for minor dose adjustments.
Rationale for Direct Conversion
Both Humalog Mix 75-25 (75% insulin lispro protamine/25% insulin lispro) and Novolog Mix 70-30 (70% insulin aspart protamine/30% insulin aspart) are premixed rapid-acting insulin analog formulations with similar pharmacodynamic profiles 1. The slight difference in the ratio of intermediate-acting to rapid-acting components (75:25 vs 70:30) is clinically insignificant for most patients and does not require dose adjustment at the time of transition 2.
Transition Protocol
Start with the same total daily dose of Novolog Mix 70-30 that the patient was receiving with Humalog Mix 75-25, divided into the same twice-daily schedule 1
Administer injections 5-15 minutes before breakfast and dinner, as both formulations are rapid-acting insulin analogs that allow for convenient pre-meal dosing 3, 4, 5
Continue all concurrent diabetes medications (particularly metformin) unless specifically contraindicated, as premixed insulin regimens work synergistically with oral agents 1
Monitoring Strategy
Check fasting and 2-hour postprandial glucose levels daily for the first 7-14 days after transition to identify any unexpected glycemic variability 6
Target fasting glucose of 90-150 mg/dL and 2-hour postprandial glucose <180 mg/dL for most patients 6
Adjust doses by 2-4 units (10-15% of current dose) every 3-7 days based on glucose patterns, if needed 1
Monitor for hypoglycemia, particularly nocturnal hypoglycemia, though both formulations have comparable low rates of hypoglycemic events 3, 7, 4
Expected Outcomes
Both Humalog Mix 75-25 and Novolog Mix 70-30 provide superior postprandial glucose control compared to older human insulin mixtures (NPH/regular 70/30), with lower 2-hour postprandial glucose excursions and improved 24-hour glucose profiles 3, 7, 5. The transition between these two rapid-acting analog mixtures should maintain glycemic control without significant changes in efficacy 4.
Common Pitfalls to Avoid
Do not reduce the dose prophylactically at the time of transition—these formulations are bioequivalent enough that a 1:1 conversion is appropriate, with adjustments made only if glucose monitoring reveals a pattern requiring change 1, 2
Avoid mixing Novolog Mix 70-30 with any other insulin in the same syringe, as premixed formulations are designed for use as-is 2
Ensure patients understand the injection timing remains 5-15 minutes before meals, not 30 minutes before as required with older human insulin mixtures 4, 5
Do not use concentrated insulin syringes (U-500) with U-100 formulations to prevent dosing errors 1