Azathioprine is a prescription immunosuppressant doctors use to calm an overactive immune system. You’ll see it for conditions like rheumatoid arthritis, inflammatory bowel disease (Crohn’s, ulcerative colitis), and to prevent organ transplant rejection. It’s not a pain pill — it reduces immune activity over weeks to months.
Typical adult dosing sits around 1–3 mg/kg per day, but your doctor will pick an exact dose based on your weight, condition, and labs. Expect a slow start: benefits can take 6–12 weeks or longer. Don’t stop it suddenly without talking to your prescriber; abrupt changes can flare your condition or cause other problems.
Before starting, many clinics check TPMT activity (an enzyme test). Why? Low TPMT raises the risk of severe bone marrow suppression. If TPMT is low, your doctor will lower the dose or choose a different drug.
Azathioprine can cause nausea, liver enzyme changes, and low blood counts. The most serious risk is bone marrow suppression, which shows up as easy bruising, unusual bleeding, persistent fever, or sore throat. Call your provider right away if that happens.
Routine monitoring is part of treatment. Expect blood tests often at first (weekly or every two weeks for the first month or two), then monthly or every few months once your numbers are stable. Tests usually include a complete blood count (CBC) and liver function tests (LFTs).
Drug interactions matter. Allopurinol (for gout) raises azathioprine toxicity — doctors usually cut the azathioprine dose to about a quarter if both are needed. Other interactions can occur, so always tell your provider about all medicines, supplements, and herbs you use.
Infection risk goes up while your immune system is suppressed. Avoid live vaccines while on azathioprine and be cautious around people with contagious infections. If you develop a fever, chills, or a bad sore throat, treat it seriously and contact your healthcare team.
Pregnancy and breastfeeding: azathioprine is sometimes used in pregnancy for certain autoimmune diseases, but the choice is personal and should be made with your specialist. Don’t change or stop treatment without discussing risks and benefits with your clinician.
Practical tips: take pills with food if they upset your stomach, store them at room temperature away from moisture, and keep a personal record of lab dates and results. If you miss a dose, check with your provider or pharmacist — don’t double up unless instructed.
Want to learn more? Ask your doctor for plain-language resources about TPMT testing, expected side effects, and the monitoring schedule. Staying informed and keeping up with labs makes azathioprine much safer and more effective.
Azathioprine has a significant role in managing autoimmune diseases. This article explores how this medication works, its benefits and risks, how it compares to other treatments, and practical tips for patients. The goal is to provide a clear and helpful guide for those seeking to understand this medicine.