What the label lists and what reports show
Azathioprine side effects
Azathioprine's FDA label lists its adverse reactions in its own words. FAERS holds 89,586 reports naming it through July 30, 2026; the reaction reported most often, leaving out the conditions it is used for, product-use terms and outcomes, is arthralgia (6,254 reports).
- Generic listed
- Boxed warning
Check it at the source: the azathioprine FDA label on DailyMed (effective November 8, 2025, Sebela Pharmaceuticals Inc.); the FDA FAERS public dashboard.
What does the label list?
From the label: adverse reactionsThe principal and potentially serious toxic effects of IMURAN are hematologic and gastrointestinal. The risks of secondary infection and malignancy are also significant (see WARNINGS ). The frequency and severity of adverse reactions depend on the dose and duration of IMURAN as well as on the patient's underlying disease or concomitant therapies. The incidence of hematologic toxicities and neoplasia encountered in groups of renal homograft recipients is significantly higher than that in studies employing IMURAN for rheumatoid arthritis. The relative incidences in clinical studies are summarized below: * Data on the rate and risk of neoplasia among persons with rheumatoid arthritis treated with azathioprine are limited. The incidence of lymphoproliferative disease in patients with RA appears to be significantly higher than that in the general population. …
A table the label prints in its adverse reactions section without a title; its column headings name the groups compared
This table is printed in the AZATHIOPRINE label published by Amneal Pharmaceuticals NY LLC of February 2, 2021; the label quoted above does not print one.
| Toxicity | Renal Homograft | Rheumatoid Arthritis |
|---|---|---|
| Leukopenia (any degree) | >50% | 28% |
| <2500 cells/mm 3 | 16% | 5.3% |
| Infections | 20% | <1% |
| Lymphoma | 0.5% | |
| Others | 2.8% |
Rows and numbers as the label prints them, under its own column headings (the first rows of a longer table where it runs on). A reaction in a trial table is not necessarily caused by the medicine, and trials differ from everyday use.
Source: FDA drug label, NDA016324 (Legacy), as published by Sebela Pharmaceuticals Inc., effective November 8, 2025 (SPL set 606101a0-6244-7eff-e053-2a91aa0acadd), via openFDA; the full label on DailyMed
What do FAERS reports show?
89,586 reports list azathioprine among the medicines taken, each a report of something that happened, not proof the medicine caused it; 9,288 are coded as a death and 31,035 as a hospital stay. Counts follow how widely a medicine is used and watched, and they are not a measure of how risky it is. Of the 19 reactions below, 7 are named by the same term (in US spelling) in the label's adverse reactions, warnings or patient leaflet; a reaction the label does not name may still be there under another word, and a report does not show that the medicine caused it.
Reports received each year
The 25 most reported reactions
Source: FDA Adverse Event Reporting System (FAERS) via openFDA, reports through July 30, 2026; reactions as MedDRA preferred terms
What next?
- Azathioprine: the full record
- label, generics, price, shortages, recalls
- Report a side effect to the FDA
- MedWatch
- Side effects hub
- the most reported medicines and reactions