Inside Warning Letters: A Statistical Update

On October 3, 2025, FDLI published an article analyzing Warning Letters (WLs) issued since January 9, 2020 by Hyman, Phelps & McNamara P.C.’s Véronique Li and Jeff Gibbs.

The in-depth analysis identified posting and issuance patterns, the length of time between milestone activities such as the conclusion of some FDA activity (e.g., inspection or promotional review) and issuance of a WL, volume trends over time, and trends in citations.

Given that WLs are issued on average 124 days after an inspection, companies should not interpret the absence of a WL within 30 working days as meaning that no WL is forthcoming. Rather, they should look to observations in the Form FDA 483 and other WLs to aid in predicting whether they are likely to receive one themselves. While the circumstances will vary for individual companies, knowing these patterns can help companies understand the probabilities of different outcomes.

The authors also determined that close-out letters, issued when a response demonstrates that violations have been corrected, or implementation of corrective actions was adequate, or a follow-up inspection does not reveal other significant violations, are becoming rarer. They caution that the number of WLs that have not received a close-out letter will grow unless FDA changes priorities or resource allocations particularly in light of recent reductions in FDA personnel.