Yes. 106 FDA-approved labels for Metronidazole carry a boxed warning, and its subject is metronidazole has been shown to be carcinogenic in mice and rats (see precautions ). 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 Metronidazole warning opens on one specific label, identified underneath it. Of the 25 Metronidazole labels sampled, 2 carried materially different wordings and this was the most common, used by 24 of them.
WARNING Metronidazole has been shown to be carcinogenic in mice and rats (see PRECAUTIONS ). Unnecessary use of the drug should be avoided. Its use should be reserved for the conditions described in the INDICATIONS AND USAGE section below.
METRONIDAZOLE, A-S Medication Solutions, label version effective 18 March 2026. 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 25 Metronidazole labels sampled for this page, 2 carried materially different wordings of the same warning, and the version quoted above was used by 24 of them.
The hazard does not change between those 2 versions. Only the sentences do, which is why a refill from a different manufacturer can carry warning text that reads differently without anything about Metronidazole or its risks having changed.
Metronidazole is dispensed under 106 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 Metronidazole have a black box warning?
Yes. 106 FDA-approved labels for Metronidazole carry a boxed warning, and its subject is metronidazole has been shown to be carcinogenic in mice and rats (see precautions ). 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 Metronidazole 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 18 March 2026, the warning concerns metronidazole has been shown to be carcinogenic in mice and rats (see precautions ). The full text is linked so the exact version can be read rather than summarised.
Does the Metronidazole boxed warning mean the drug is unsafe or being withdrawn?
No. It means the FDA requires the risk of metronidazole has been shown to be carcinogenic in mice and rats (see precautions ) to be communicated prominently so prescribers weigh it explicitly. Metronidazole remains FDA-approved and is dispensed under 106 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 25 Metronidazole labels sampled here, 2 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 Metronidazole because of this warning?
This page does not answer that and cannot. The warning about metronidazole has been shown to be carcinogenic in mice and rats (see precautions ) is written for a prescriber deciding whether Metronidazole 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 Metronidazole label, linked below by its DailyMed set identifier so the exact version can be opened rather than taken on trust. The figure of 106 labels, and the count of 2 distinct wordings among 25 sampled, were computed from the openFDA labelling API on 30 August 2026.
- METRONIDAZOLE prescribing information, A-S Medication Solutions, effective 18 March 2026.
- 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.