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Azathioprine

Brand names: Imuran, Azasan

Azathioprine calms the immune system. It treats Crohn's disease, ulcerative colitis, autoimmune diseases, and prevents organ rejection.

Brand namesImuran, Azasan
Type of medicineImmunosuppressant
Prescription?Prescription
ImportantThis page is general information, not a prescription. Don't start, stop, or change a medicine without talking to your provider or pharmacist.

Overview

A TPMT blood test before starting shows whether you need a lower dose.

What it's used for

  • Crohn's disease and ulcerative colitis (off-label)
  • Rheumatoid arthritis
  • Lupus and other autoimmune diseases
  • Kidney transplant

How to take it

  • Take it after meals to reduce nausea.
  • Keep all blood test appointments.

Your dose depends on your health and other medicines. Always follow your prescription label, and ask your pharmacist if anything is unclear.

Side effects

Common side effects

  • Nausea
  • Tiredness
Call your provider todayFever, chills, sore throat, or other signs of infection
Call 911Severe belly pain (pancreatitis)
Call your provider todayUnusual bruising, bleeding, or paleness
Call your provider todayYellow skin or eyes

Warnings

  • Boxed warning: higher risk of some cancers, including lymphoma and skin cancer. Use sunscreen.
  • It weakens the immune system, raising the risk of serious infections. Avoid live vaccines.

Other medicines, foods, and alcohol

  • Allopurinol and febuxostat raise its level dangerously.
  • It can weaken warfarin.

Tell your provider and pharmacist about every medicine, vitamin, and supplement you take.

Pregnancy and breastfeeding

Sometimes continued in pregnancy. Talk with your provider.

Missed doses, overdose, and storage

If you miss a dose

Take it as soon as you remember, unless it's almost time for your next dose. Then skip the missed dose. Don't take two doses at once.

If someone takes too much

Call Poison Control at 1-800-222-1222 or get help online at poison.org. Call 911 if the person collapses, has a seizure, has trouble breathing, or can't be woken.

Storing it

Store at room temperature, away from heat and moisture (not in the bathroom), and out of reach of children and pets.

Conditions it's used for

Sources

Last updated 2026-11-13.