# Failure to Warn

> A product liability claim alleging that a manufacturer did not adequately communicate known or knowable risks associated with its product.

**Category:** Legal Theory
**Canonical URL:** https://drugsmonitor.com/glossary/failure-to-warn
**Last updated:** 2026-06-11

Failure to warn is the most common legal theory in pharmaceutical litigation. Plaintiffs allege that the drug manufacturer knew or should have known about a risk but failed to include adequate warnings in the label, package insert, or other communications.

The learned intermediary doctrine generally holds that manufacturers satisfy their duty by warning physicians, who then advise patients. However, direct-to-consumer advertising has created exceptions in some jurisdictions.

Evidence of failure to warn often includes internal company documents, FDA warning letters, adverse event reports, and comparative labeling practices. Post-market label changes can serve as evidence that earlier warnings were inadequate.

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*Glossary entry from DrugsMonitor.com.*