Intermediate-Acting (NPH) Insulin: What It Means
App Library Tools Pricing Download
[Glossary · Compound types]

Intermediate-acting insulin

Also called NPH insulin, isophane insulin, insulin N, neutral protamine Hagedorn · Reviewed

Definition: Intermediate-acting insulin, also called NPH or isophane insulin, is human insulin bound to protamine so it is absorbed more slowly. NIDDK lists its onset at 2 to 4 hours, its peak at 4 to 12 hours and its duration at 12 to 18 hours. Humulin N and Novolin N are the US products.

What the labels say

  • It is a suspension, so it should look evenly cloudy after mixing. The Humulin N label says not to use it if particles are seen.
  • It goes under the skin only, never into a vein and never in an insulin pump.
  • In a syringe it may be mixed with Humulin R or Humalog, drawing the clear insulin in first, then injecting right away.
  • The labels give no fixed starting dose or number of injections a day; the dose is set for each person.

Storage differs by package: at room temperature, a Humulin N vial lasts 31 days in total and a KwikPen 14 days.

How it compares

NPH has a peak, unlike long-acting basal insulins, which NIDDK lists as not peaking. It is also the slower half of most premixed insulins: Novolin 70/30 is 70% NPH and 30% regular insulin. The Humulin N label says how fast it is absorbed depends on the injection site, physical activity and other factors.

Why it matters for your log

A pen and a vial of the same NPH insulin expire at different times once out of the fridge. Logging the open date for each one shows when it reaches its limit.

Read more on Dose Track: Humulin N side effects · Novolin N side effects · How to store Humulin N · How to store Novolin N

General education drawn from labels and published studies, not personal medical advice. Your prescriber, pharmacist and the label that came with your product are the final word.
Regular insulinRegular insulin is short-acting human insulin, the R in Humulin R and Novolin R. NIDDK lists its onset at… Premixed insulinPremixed insulin is one product holding two insulins in fixed amounts: a slower, intermediate-acting part… Basal insulinBasal insulin is long-acting insulin, usually injected once a day, that gives a steady background level of… Rapid-acting insulinRapid-acting insulin is a mealtime insulin that starts working quickly and wears off within hours. NIDDK… Beyond-use date (BUD)A beyond-use date (BUD) is the date after which a compounded or opened medicine should not be used. It is…

Frequently asked questions

What does NPH stand for?+
Neutral protamine Hagedorn. The labels call it insulin isophane human. The protamine slows absorption so it lasts longer than regular insulin.
Why is NPH insulin cloudy?+
It is a suspension, not a solution. The labels say it is mixed until evenly cloudy before each dose.

Sources

  1. NIDDK (NIH): Insulin, medicines and other diabetes treatments
  2. Humulin N (insulin isophane human) US prescribing information, DailyMed
  3. Novolin N (insulin isophane human) US prescribing information, DailyMed
  4. Novolin 70/30 (insulin isophane human and insulin human) US prescribing information, DailyMed

All glossary terms · Goals and conditions · Compound guides · Common questions · Help center