Yes. 18 FDA-approved labels for Azathioprine carry a boxed warning, and its subject is malignancy chronic immunosuppression with azathioprine, a purine antimetabolite increases risk of malignancy in humans. A boxed warning is the most serious warning the FDA requires on a prescription label. It is applied to the drug and to the situations in which it is used, not to any particular person taking it.
What the warning says
Below is how the Azathioprine warning opens on one specific label, identified underneath it. Of the 18 Azathioprine labels sampled, 7 carried materially different wordings and this was the most common, used by 8 of them.
WARNING - MALIGNANCY Chronic immunosuppression with azathioprine, a purine antimetabolite increases risk of malignancy in humans. Reports of malignancy include post-transplant lymphoma and hepatosplenic T-cell lymphoma (HSTCL) in patients with inflammatory bowel disease. Physicians using this drug should be very familiar with this risk as well as with the mutagenic potential to both men and women and with possible hematologic toxicities. Physicians should inform patients of the risk of malignancy with azathioprine. See WARNINGS .
AZATHIOPRINE, American Health Packaging, label version effective 19 May 2025. read the full label on DailyMed.Why the wording differs between manufacturers
There is no single official text of a boxed warning. The FDA sets what a warning must cover, and each manufacturer writes its own label within that. Of the 18 Azathioprine labels sampled for this page, 7 carried materially different wordings of the same warning, and the version quoted above was used by 8 of them.
The hazard does not change between those 7 versions. Only the sentences do, which is why a refill from a different manufacturer can carry warning text that reads differently without anything about Azathioprine or its risks having changed.
Azathioprine is dispensed under 18 current FDA labels despite this warning, which is the point worth holding onto: a boxed warning is a disclosure requirement, not a verdict. What a boxed warning does and does not mean sets out the distinction.
Common questions
Does Azathioprine have a black box warning?
Yes. 18 FDA-approved labels for Azathioprine carry a boxed warning, and its subject is malignancy chronic immunosuppression with azathioprine, a purine antimetabolite increases risk of malignancy in humans. A boxed warning is the strongest warning the FDA requires on a prescription label, and it is applied to the drug, not to any individual taking it.
What does the Azathioprine boxed warning say?
The wording is set by each manufacturer within FDA requirements, so it varies. In the version quoted on this page, taken from a label effective 19 May 2025, the warning concerns malignancy chronic immunosuppression with azathioprine, a purine antimetabolite increases risk of malignancy in humans. The full text is linked so the exact version can be read rather than summarised.
Does the Azathioprine boxed warning mean the drug is unsafe or being withdrawn?
No. It means the FDA requires the risk of malignancy chronic immunosuppression with azathioprine, a purine antimetabolite increases risk of malignancy in humans to be communicated prominently so prescribers weigh it explicitly. Azathioprine remains FDA-approved and is dispensed under 18 current labels. A boxed warning is a disclosure requirement, not a judgement that a drug should not be used.
Why do different pharmacies show different warning text for the same drug?
Because each manufacturer writes its own label within the FDA's requirements. Of 18 Azathioprine labels sampled here, 7 carried materially different wordings of the same warning. The hazard described is the same; the sentences are not. This is a common source of confusion when a prescription is refilled with a different manufacturer's product.
Should I stop taking Azathioprine because of this warning?
This page does not answer that and cannot. The warning about malignancy chronic immunosuppression with azathioprine, a purine antimetabolite increases risk of malignancy in humans is written for a prescriber deciding whether Azathioprine suits a particular patient, and stopping a prescribed medicine carries its own risks that this page knows nothing about. Raise it with the prescriber or a pharmacist, who can see the whole picture.
Where this page's information comes from
The quotation above is from one Azathioprine label, linked below by its DailyMed set identifier so the exact version can be opened rather than taken on trust. The figure of 18 labels, and the count of 7 distinct wordings among 18 sampled, were computed from the openFDA labelling API on 30 August 2026.
- AZATHIOPRINE prescribing information, American Health Packaging, effective 19 May 2025.
- openFDA drug labelling API, the source of the label counts and variant counts on this page.
Labels are revised over time. The version linked above is the one this page was written against, and a newer revision may differ. Counts reflect the labels present in openFDA on the retrieval date.