Warning letters typically follow an inspection or review in which FDA finds significant violations, and they usually ask for a written response within 15 business days describing how and when the company will correct the issues. They differ from a Form 483, which lists inspectional observations, and from untitled letters, which generally address violations of lesser regulatory significance. If violations continue, FDA can escalate to further enforcement such as seizure, injunction or import alerts.
Why it matters for labeling
Labeling and promotional content are common subjects: misbranded or unapproved claims, labeling that doesn't match what was approved, and records and computerized system failures. FDA's April 2026 warning letter to a manufacturer was notable because it cited the quality unit's failure to review AI-generated specifications and production records before they were used, under 21 CFR 211.22(c).
Common mistakes
- Treating a 483 response as optional or a formality
- Responses that fix the specific example but not the system behind it
- No follow-up evidence after the initial response
- Not reviewing your own materials against recent letters, which show where FDA is looking