Short answer: Both are rapid-acting mealtime insulins approved for adults and children with diabetes. Humalog (insulin lispro) is injected within 15 minutes before a meal or right after it, and also comes in a stronger U-200 pen. NovoLog (insulin aspart) is injected 5 to 10 minutes before a meal and comes only as U-100.12 Opened pens of both last 28 days at room temperature.
| Humalog (insulin lispro) | NovoLog (insulin aspart) | |
|---|---|---|
| Type | Rapid-acting insulin analog1 | Rapid-acting insulin analog2 |
| When to inject | Within 15 minutes before a meal or immediately after a meal1 | Within 5 to 10 minutes before a meal2 |
| Strengths | U-100 and U-200 (200 units/mL, KwikPen only)1 | U-100 only2 |
| Forms | 10 mL and 3 mL vials, KwikPen, Tempo Pen, Junior KwikPen, cartridges1 | 10 mL vial, FlexPen, FlexTouch, PenFill cartridges2 |
| Pen dosing | KwikPen and Tempo Pen: 1-unit steps, up to 60 units per injection. Junior KwikPen: half-unit steps, up to 30 units1 | FlexPen and FlexTouch: 1-unit steps2 |
| Insulin pump | U-100 only; change the reservoir at least every 7 days1 | Yes; change the reservoir at least every 7 days2 |
| Time to peak level | Peak serum levels 30 to 90 minutes after a dose in healthy volunteers1 | Median 40 to 50 minutes; peak glucose-lowering effect 1 to 3 hours; effect lasts 3 to 5 hours2 |
| Half-life under the skin | About 1 hour1 | About 81 minutes2 |
| Children in label studies | Type 1 diabetes, ages 3 and older1 | Type 1 diabetes, ages 6 to 182 |
| Opened (in use) | 28 days; pens and cartridges at room temperature only1 | 28 days; pens and cartridges at room temperature only2 |
On the labels, yes. Humalog may be injected up to 15 minutes before eating or immediately after the meal.1 NovoLog's label gives one window: 5 to 10 minutes before the meal.2 Both labels say a mealtime insulin injected under the skin is generally used with an intermediate- or long-acting insulin, and both note that the time course of action varies between people and even in the same person.12
A KwikPen holding 200 units per mL, so the same number of units sits in half the liquid. The dose window shows units, and the label says not to convert doses. U-200 must not be moved into a syringe, used in a pump, given into a vein or mixed with any other insulin.1 NovoLog has no U-200 form.2
Neither label gives a conversion between the two. Both say a different dose may be needed when switching from another insulin, and both ask for more frequent glucose checks during any change.12 Your diabetes team sets the plan.
Unopened, both stay in the fridge until the expiration date, or 28 days at room temperature up to 86°F. Once opened, both last 28 days; vials may be refrigerated or not, while pens and cartridges stay at room temperature.12 Humalog counts unopened and opened room-temperature days together.1 For NovoLog in a pump, total in-use time is 19 days, including 7 days in the pump.2
Full details: how to store Humalog, how to store NovoLog, and what the labels say if you miss a Humalog dose or miss a NovoLog dose.