Insulins

NPH (intermediate-acting) insulin: Humulin N, Novolin N

isophane human insulin · Intermediate-acting insulin · Eli Lilly; Novo Nordisk

✓Last reviewed · Written by Dr. George Grunberger · Medical review: pending — clinician review in progress · How we review

In short

NPH insulin (isophane human insulin) is an intermediate-acting insulin made by Eli Lilly; Novo Nordisk, used for basal blood sugar control in diabetes. Schedule: once or twice daily. It is prescription-only in the US and Canada.

FormVials, pens
How oftenOnce or twice daily
United StatesFDA-approved; available over the counter at many US pharmacies.
CanadaAvailable in Canada.
PrescriptionRequired

What it is used for

  • Basal blood sugar control in diabetes

NPH insulin dosage

Per the official label. Your prescriber sets your dose — never change it on your own.

NPH insulin label dosing schedule
1DoseIndividualized in units

How to take it

Roll gently to resuspend (cloudy insulin) before each injection; do not shake hard.

Storage

Unopened: refrigerate. In use: per labeling.

How long it works compared with other insulins

How long each insulin type worksApproximate duration of action: rapid-acting about 4 hours, regular about 6 hours, NPH 12 to 18 hours with a peak at 4 to 12 hours, glargine about 24 hours, degludec up to 42 hours, icodec about one week.0 h12 h24 h36 h48 hRapid-acting (lispro, aspart, glulisine)Short-acting (regular)Intermediate (NPH)Long-acting (glargine)Ultra-long (degludec)Once-weekly (icodec)≈ 1 week →
Typical time-action profiles from product labels (darker band = peak). Your response can differ — follow your own plan.

Side effects

Common

  • Low blood sugar (hypoglycemia)
  • Injection-site reactions
  • Weight gain
  • Lipodystrophy or skin thickening at repeated injection sites

Serious — get medical help

  • Severe hypoglycemia (confusion, seizures, loss of consciousness)
  • Low potassium (hypokalemia)
  • Fluid retention and heart failure when combined with thiazolidinediones
  • Serious allergic reactions

Who should not use it

  • During an episode of low blood sugar
  • Never share pens or needles, even if the needle is changed
  • Do not switch insulin type, brand or concentration without your prescriber

Cost

Low-cost option.

GLP-1 cost without insurance →

How to buy NPH insulin legally

  1. Get a prescription from your doctor or a licensed telehealth provider.
  2. Fill it at a licensed pharmacy, or through the manufacturer's self-pay pharmacy.
  3. Verify any online pharmacy first (US: safe.pharmacy; Canada: your provincial pharmacy college register).

Buying legally in the USA → Buying legally in Canada →

Also searched as: Humulin N, Novolin N, NPH, intermediate-acting insulin, cloudy insulin

Sources

Checked against these primary sources on .

InsulinsRegular (short-acting) insulin: Humulin R, Novolin Rhuman insulin (regular) · Before mealsInsulinsInsulin glargine: Lantus, Basaglar, Semglee, Rezvoglar, Toujeoinsulin glargine · Once dailyInsulinsPremixed insulins: Humalog Mix, NovoLog Mix, Humulin/Novolin 70/30premixed insulin · Usually twice daily with meals
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