What FDA Warning Letters Stopped Being About
In 2020, 63% of every warning letter FDA sent a drug, device or biologics company mentioned COVID. In 2025 it was one letter out of 403.
That is not a small shift in emphasis. For three years the agency's written enforcement was largely pointed somewhere other than manufacturing, and if your sense of what FDA cares about was formed in that window, it is out of date.
We read the text of 1,976 warning letters issued by CDER, CDRH and CBER
between 2018 and September 2026, assembled from FDA's own sitemap because FDA
publishes no warning letter API. Every number below is produced by a script in the repository,
scripts/analyze-warning-letters.py, so it can be re-run and checked. The
letters themselves are searchable in our
warning letter search.
The quality unit disappeared, then came back
The clearest signal is what stopped being cited. A quality unit finding is the most basic CGMP citation there is: the unit that is supposed to approve and reject materials and procedures did not do its job.
| Share of letters citing | 2018 | 2020 | 2021 | 2024 | 2026 |
|---|---|---|---|---|---|
| Quality unit | 38% | 11% | 3% | 28% | 25% |
| Stability | 30% | 5% | 6% | 21% | 10% |
| Out-of-specification | 29% | 8% | 3% | 14% | 12% |
| Process validation | 25% | 7% | 5% | 20% | 13% |
| Data integrity | 17% | 4% | 2% | 11% | 8% |
In 2021 a quality unit citation appeared in 3% of letters, down from 38% three years earlier. Out-of-specification handling and data integrity fell just as far.
The natural reading is that manufacturers briefly got much better at pharmaceutical quality. That is not what happened.
What crowded it out
The same years show the opposite movement in two other citations:
| Share of letters citing | 2018 | 2020 | 2022 | 2026 |
|---|---|---|---|---|
| Marketing claims | 6% | 50% | 26% | 1% |
| Unapproved new drug | 10% | 70% | 47% | 45% |
| COVID mentioned | 0% | 63% | 40% | 1.5% |
Half of all letters in 2020 turned on marketing claims: products sold to treat or prevent a disease without an approval to say so. Seventy percent cited an unapproved new drug.
FDA did not stop caring about manufacturing. It redirected finite inspection and enforcement capacity toward products being sold into a public health emergency, while routine surveillance inspections were themselves curtailed. Warning letters follow inspections. Fewer inspections of manufacturing sites means fewer manufacturing citations, and it says nothing about the state of those sites.
That matters for anyone benchmarking. If you compared your risk profile against 2021 warning letters, you compared it against a year in which FDA was barely writing about manufacturing at all.
Manufacturing enforcement is back
By 2024 the quality unit is cited in 28% of letters, stability in 21%, process validation in 20%. Marketing claims are down to 3%. The 2026 figures hold near the same level.
In other words, the pre-2020 pattern reasserted itself, with one exception.
The exception: unapproved drugs did not go back down
Marketing claims collapsed from 50% to 1%. Unapproved new drug citations did not: they sit at 45% in 2026, still four times the 2018 rate.
What they are about has changed completely. Of the 65 letters in 2026 citing an unapproved new drug, the recurring subjects are:
- compounding, by a wide margin
- stem cell products
- tirzepatide, semaglutide and other peptides
- nicotine products
This is the GLP-1 compounding wave arriving in the enforcement record. The statutory hook is the same one FDA used against COVID cures in 2020, applied to a completely different market.
If you are a compounder, a peptide supplier, or anyone marketing a product whose approved equivalent exists, this is the live enforcement front.
What to take from this
Benchmark against the right years. 2020 to 2022 is not a normal baseline for anything. Use 2018 to 2019, or 2024 onward.
A quiet category is not a safe one. Manufacturing citations fell 90% and then fully recovered, without the underlying risk changing. Enforcement attention is a budget, and it moves.
Watch what the statutory hook gets pointed at next. The unapproved new drug provision went from COVID cures to compounded GLP-1s in about four years. The provision did not change. The market did.
How this was assembled
FDA publishes warning letters as individual web pages and provides no API for them. The public table serves 1,792 letters and its date filter does not work. FDA's sitemap, however, lists every published letter: 7,326 of them, of which 1,976 come from CDER, CDRH and CBER.
Each letter's full text was scanned for the citations above. Every figure here is a share of that year's letters, never a raw count. FDA de-publishes older letters, so counts before 2018 are thin for reasons unrelated to how many were issued, and treating them as enforcement volume would be wrong.
You can search the same corpus, filtered by deficiency, company, office and year, with our warning letter search. Background on what a warning letter is and what a response has to contain is in the glossary, along with the Form 483 that usually precedes one.