How fast does NPH insulin start working?

It usually starts lowering blood sugar within 90 minutes of injection.

When is the peak effect?

Peak effect occurs after about 8 hours.

How long does it last?

The total duration of action is around 14 hours.

Intermediate-acting (NPH)

Intermediate-acting (NPH) insulins have onset of 1–2 hours, peak between 4–12 hours, and last up to 18 hours. Usually taken once or twice daily.

Onset

min

Fast

Time until it starts working after injection.

Peak

8 h

When effect is strongest (may be minimal for some long-acting insulins).

Duration

approx

Total time the insulin continues to act.

Activity curve (illustrative)

This stylized curve shows a typical onset, peak, and duration profile for NPH insulins. For education only.

How it works

NPH

Intermediate-acting insulins (NPH) provide a slower and more prolonged insulin effect. They begin working within 1–2 hours, peak between 4–12 hours, and last about 12–18 hours.

Typical use

Commonly taken once or twice daily to provide basal (background) insulin coverage. Often used in combination with short- or rapid-acting insulins.

Storage & handling

Store unopened vials or pens at 2–8°C. Roll gently to mix before injection. Once opened, can be kept at room temperature for up to 28 days.

Frequently asked questions

What is NPH insulin and when is it used?

How do I time injections of NPH given Indian lifestyle (meals, school, work)?

Do I still need mealtime insulin if I’m using NPH?

What about mixing and injection in our climate?

Disclaimer: Educational content only; not medical advice. Always consult your healthcare professional.