Novolin 70/30 is Neither Purely Short-Acting Nor Long-Acting—It's a Premixed Combination
Novolin 70/30 is a premixed insulin containing 70% intermediate-acting NPH insulin and 30% short-acting regular human insulin, making it a dual-action formulation rather than exclusively short or long-acting 1.
Understanding the Components
The formulation combines two distinct insulin types with different pharmacokinetic profiles:
- 30% Regular human insulin: This is the short-acting component that begins working within 30 minutes and covers mealtime glucose spikes 1
- 70% NPH (insulin isophane): This is the intermediate-acting component that provides basal coverage for several hours 1
Clinical Implications
Novolin 70/30 must be injected approximately 30 minutes before meals because the regular insulin component requires this lead time to begin working 1. The medication is typically dosed twice daily, with each dose intended to cover two meals or a meal plus a snack 1.
Duration of Action
The intermediate-acting NPH component provides coverage that lasts longer than short-acting insulin alone but significantly shorter than true long-acting basal insulins (like glargine or detemir). This is why it requires twice-daily dosing rather than once-daily administration 2.
Common Pitfall to Avoid
Do not confuse this premixed formulation with either pure short-acting insulin (like regular insulin alone) or long-acting basal insulins. The 70/30 designation specifically refers to the fixed ratio of intermediate-to-short-acting components. This fixed ratio means you cannot independently adjust the basal and prandial components—if you need that flexibility, guidelines recommend switching to a self-mixed regimen or full basal-bolus therapy 2.
The 2025 ADA guidelines note that when adding prandial insulin to NPH therapy, clinicians should consider premixed formulations like Novolin 70/30 to reduce the number of required injections 2.