Short answer: Both are premixed insulin lispro for adults, injected within 15 minutes before a meal, typically twice daily.12 The difference is the split: Mix50/50 is half rapid-acting insulin lispro and half lispro protamine; Mix75/25 is one quarter rapid-acting and three quarters protamine. Mix50/50 comes only as a KwikPen; Mix75/25 also comes in a vial. Neither label compares the two.
| Humalog Mix50/50 | Humalog Mix75/25 | |
|---|---|---|
| Split | 50% insulin lispro protamine, 50% insulin lispro1 | 75% insulin lispro protamine, 25% insulin lispro2 |
| When | Within 15 minutes before a meal, typically twice daily1 | Within 15 minutes before a meal, typically twice daily2 |
| Peak effect | Median 2 hours (range 1 to 5)1 | About 2 hours (range 1 to 6)2 |
| Glucose lowering detectable | Median 22 hours, the end of the study1 | Median 22 hours, the end of the study2 |
| Forms | 3 mL KwikPen only1 | 10 mL vial or 3 mL KwikPen2 |
| In-use storage | KwikPen 10 days, room temperature1 | KwikPen 10 days; vial 28 days2 |
| Missed dose | No rule in the label1 | No rule in the label2 |
| Boxed warning | None1 | None2 |
Both are cloudy suspensions: the KwikPen is rolled at least 10 times and turned upside down at least 10 times until evenly white. Both are injected under the skin only, never into a vein or by pump, and never mixed with other insulins. The fixed split in each does not allow separate basal and mealtime changes.12 The Mix75/25 label says its duration is similar to Humulin 70/30.2
The warnings are the same insulin set: low blood sugar, low potassium, allergy, mix-ups between insulins, never sharing a pen and heart failure with pioglitazone-type drugs.12 Which, if either, fits is for your prescriber. More detail: Humalog Mix50/50 side effects, Humalog Mix75/25 side effects, the Mix50/50 and Mix75/25 dosing schedules, the insulin lispro guide, and Humalog Mix75/25 vs NovoLog Mix 70/30: how do the premixed insulins differ?.