FDA warning letters to supplement firms: what 16 recent letters cited, and how to respond

An FDA warning letter is the agency's informal, advisory notice that it has found violations it considers significant. It asks for a written answer, usually within 15 working days, and it stays public on fda.gov. In the 16 letters to supplement firms we read, dated April 2025 to September 2026, 11 called the products unapproved new drugs, nine of them because of disease claims.

What 16 recent FDA warning letters to supplement firms cited

We opened each letter on fda.gov on 21 October 2026. Twelve turned up in a search of FDA's warning letter listing for "dietary supplement", newest first; a search of fda.gov found four more from 2025. Each one concerns products marketed or labeled as dietary supplements. It's a sample, not the whole database, and one letter can cite several problems:

What 16 FDA warning letters to supplement firms cited

Number of letters citing each problem; one letter can cite several

Unapproved new drug9 from disease claims, 2 from ingredients a supplement can't contain11 of 16

Misbranded drug: inadequate directions for use8 of 16

Manufacturing (CGMP, 21 CFR part 111)3 were inspection letters that quoted no claims8 of 16

Unsafe or unlawful ingredient2 new dietary ingredients, 2 undeclared or excluded drug ingredients4 of 16

Supplement labeling (section 403)3 of 16

Serious adverse event reporting1 of 16

"Unapproved new drug" is FDA's way of saying the claims turned a supplement into a drug. A product promoted as "intended for use in the cure, mitigation, treatment, or prevention of disease" is a drug, and a drug that isn't generally recognized as safe and effective for those uses is a new drug, which can't be sold across state lines without FDA's approval. The product doesn't change. The copy does. In two of the eleven the problem was an ingredient that can't be in a supplement at all, which is covered below.

Eight letters added a second charge that follows from the first: misbranding, for inadequate directions for use. One letter gives FDA's reasoning: for diseases a layperson can't diagnose, "it is impossible to write adequate directions for a layperson to use your product safely."

Manufacturing came up just as often. Eight letters cited the current good manufacturing practice (CGMP) rule for supplements, 21 CFR part 111, under which products "prepared, packed, or held under conditions that do not meet CGMP requirements" are adulterated. Three of those followed inspections and quoted no claims; the other five paired the manufacturing failures with disease claims.

The rest were about what went into the bottle or onto the label. Four letters cited an unsafe or unlawful ingredient. Three cited labeling provisions in section 403 of the Federal Food, Drug, and Cosmetic Act, among them an undeclared major food allergen and nutrition labeling. One cited the reporting of serious adverse events.

Read the counts as patterns in 16 letters, not as FDA's rates: 12 of the 16 are from 2026, so this is a picture of recent letters, not a trend. One pattern is worth remembering anyway: five of the letters quoted no claim at all. No copywriter could have prevented those, because they were about the factory or the formula.

The firm's own website was in every letter that quoted a claim

Eleven letters quoted claims and said where FDA found them. The firm's own site appeared in all eleven:

Where FDA found the claims it quoted

The 11 letters in the sample that quoted claims

11 of 11quoted the firm's own website, with blog posts in 3

3 of 11quoted posts on social media

2 of 11quoted customer testimonials

0cited hashtags, metatags or a marketplace listing

Social media turned up in only three, so an audit that starts on Instagram starts in the wrong place. What the letters show instead is how much of a website FDA reads:

• Pages that don't sell. One letter cited the about-us page alongside the product pages (the July 2026 letter); another quoted help and FAQ pages.
• Blog posts. Three letters read posts on the firm's blog as claims for its products, posts about an ingredient included. One of the cited posts linked to an outside Mayo Clinic article (the April 2025 letter).
• Testimonials. One letter quoted a customer testimonial posted on Instagram, another a "Satisfied Customers" slideshow on the firm's own site (the January 2026 letter).
• Old posts. A June 2026 letter quoted Instagram testimonials from 2018 and Facebook posts, one of them from 2021 (the letter). A December 2025 letter quoted Facebook posts from September 2024.
• The label. Two letters quoted claims printed on the product's own label.

A VSL page is part of your website, so its script, its on-screen text, the testimonials in the video and the comments under it belong in the same review as the product pages.

So do product names. One letter in the sample covered two products with a disease in their names (the May 2026 letter). FDA listed both names among the claims, and of one it wrote: "Name of product is a claim". A 2021 joint FDA–FTC letter, below, makes the same point. FDA's ten criteria for when a statement becomes a disease claim, names and pictures included, are in our post on structure/function claims.

Five kinds of claim that drew letters, and what to say instead

The claim letters repeat a handful of patterns. Each tab holds a fictional line written to match one of them, what the sample shows about it, and a fix. A rewritten claim still needs evidence for your product, and some lines can only be cut:

Claims that drew letters, and what to do instead

Fictional lines written to match patterns in the 16 letters

SymptomsTestimonialsBlog postsLabelsProduct names

A promise about a condition's symptoms

Burning, tingling and numbness are symptoms, so the line is a disease claim without naming a disease. One letter quoted a site that called its nerve formula clinically proven to reduce such symptoms by about 76%.

“Clinically shown to calm the burning and tingling in your feet.”

Instead: describe only the normal function your evidence supports for this formula, with the disclaimer, and drop any “clinically proven” figure that no study of your product backs.

A customer's result that is a disease result

A testimonial you publish is a claim you make. One letter quoted a 2018 Instagram testimonial about a customer's drop in daily glucose levels.

“Two weeks in, my blood sugar readings are finally coming down.”

Instead: leave it out, on the page, in the video and in the comments. Keep the testimonials that describe experiences your evidence supports.

An article about an ingredient

Three letters read posts on the firm's own blog as claims for its products, posts about an ingredient included.

“The antioxidants in this berry may lower your risk of heart disease.”

Instead: take the post down, or rewrite it to the structure/function claims you can support. It sits on the site that sells the product, so treat it as product copy.

A disease claim on the bottle

Two letters quoted claims printed on the label itself, one of them that the product may lower blood pressure. Hedging with “may” didn't keep it out of the letter.

“May help lower blood pressure.”

Instead: change the label, then remove the line from every page, ad and email that repeats it.

A name built on a disease

One letter in the sample counted two product names among the claims it quoted, both naming a disease, and of one FDA wrote: “Name of product is a claim”. A 2021 joint FDA–FTC letter says claims can be made through a product name, too.

A joint supplement called “ArthriFree” (fictional).

Instead: name the product for what it is, not for the condition its buyers have.

Each fix looks small on the page. In practice it means finding every place the line appears: the label, the product page, the VSL, the ads, the emails, and the post from three years ago that nobody remembers writing.

When the problem is the factory or the formula

The three manufacturing letters that quoted no claims all followed inspections, each after FDA had listed its observations on a Form FDA 483. In one, FDA judged the firm's responses to those observations inadequate (the August 2026 letter). A fourth letter, which also cited claims, listed observations repeated from a 483 issued in 2021. For a brand that buys from a manufacturer, the lesson is to read its FDA record before you sign, one of the checks in our manufacturer post.

The ingredient letters are the bluntest. Two were about new dietary ingredients, ones not marketed in the US before 15 October 1994, and in both FDA said there wasn't adequate information to show the ingredient doesn't present "a significant or unreasonable risk of illness or injury". One concerned Amanita muscaria. The other concerned a peptide sold under a "GLP-1" name, which the firm went on marketing, FDA says, after FDA had objected to two notifications for it (the letter). Neither letter quoted a claim.

Two more came from FDA's Center for Drug Evaluation and Research rather than the Human Foods Program, which sent the other 14. Both concerned products containing drug ingredients their labels didn't declare, such as ibutamoren (MK-677), which FDA says is excluded from the definition of a dietary supplement. Both were marketed or labeled as supplements, and the label didn't make them one.

No rewrite fixes an ingredient. The new dietary ingredient post explains the 1994 cutoff and the notification FDA expects before a new ingredient goes on sale.

How to respond to an FDA warning letter

A warning letter isn't a fine, a ban or a final decision. FDA's Regulatory Procedures Manual calls it "informal and advisory" and "the agency's principal means of achieving prompt voluntary compliance", and says it doesn't commit FDA to enforcement (RPM, chapter 4). It's still serious. FDA sends one only for violations of regulatory significance, and it issues letters "to achieve voluntary compliance and to establish prior notice": after one, nobody can say they weren't told. Nor does FDA have to send one before it acts.

From the finding to the close-out, a letter moves through five stages:

The life of a warning letter

From FDA's Regulatory Procedures Manual, its close-out page and the 16 letters

1. 1Finding
2. 2Letter
3. 3Reply
4. 4Check
5. 5Outcome

1FDA finds the violations

What happens: An inspection of a facility, or a review of the firm's website, social media and labels. The letter quotes what FDA read, with dates.

Why it matters: Everything the firm published can be quoted, and every quote can be checked line by line.

What goes wrong:

• Old posts and pages still online: the sample quotes posts from 2018 and 2021
• Inspection findings answered too thinly

2The letter is issued and posted

What happens: FDA sends the letter to the firm and later posts it on fda.gov, where it stays.

Why it matters: It's advisory but public, and it establishes that the firm was told.

What goes wrong:

• Reading it as a fine or a ban: it is neither
• Assuming it lists every problem: FDA says it is not all-inclusive

3A written reply, usually within 15 working days

What happens: Each violation, the steps taken, how a repeat is prevented, the documents that show it, and a timeline for anything not yet finished.

Why it matters: FDA judges what was corrected, not what was promised.

What goes wrong:

• Counting calendar days from the letter's date instead of working days from receipt
• Fixing the product page and forgetting the label, the blog and old posts

Read more: Structure/Function Claims: Rules, Examples, Disclaimer

4FDA verifies the corrections

What happens: Usually a follow-up inspection, or other reliable information that the violations were corrected.

Why it matters: A close-out letter needs corrections that were made and verified.

What goes wrong:

• Promises instead of evidence
• New violations found at the follow-up

5A close-out letter, or escalation

What happens: A close-out letter if the corrections hold and nothing else significant turns up. If the violations aren't corrected, legal action can follow, including seizure and injunction.

Why it matters: A close-out letter is FDA's record that the corrections were made and verified.

What goes wrong:

• Old claims creeping back into the next campaign
• Treating the close-out as permanent clearance

The clock runs in working days from the day you receive the letter, not calendar days from its date. FDA asks for a written response "usually fifteen (15) working days" after receipt, about three weeks, and all 16 letters in the sample asked for 15. The letters we checked also spell out what the reply should contain:

1. The specific steps you've taken to address each violation.
2. How you'll prevent each one from happening again, with copies of the documents that show it.
3. For anything you can't finish in 15 working days, the reason and the time it will take.
4. If you believe a product isn't in violation, your reasoning and the information that supports it.

Send it where the letter says, quoting its case number. Then expect FDA to check: a close-out letter comes only after the corrections have been made and verified, usually at a follow-up inspection, and FDA says it won't issue one "based on representations that some action will or has been taken" (FDA).

The letter stays public either way. FDA posts warning letters on fda.gov and takes one down only if it rescinds or amends it; you can ask FDA to post your response beside the letter, and FDA can decline. For the 14 letters in our sample whose posting date we could read, the gap between a letter's date and its appearance online ran from 11 to 104 days, about 25 at the median. Even a close-out isn't a clean bill of health: FDA says later inspections can look at the corrections again, and violations that come back can bring enforcement without further notice.

This section summarizes FDA's own documents; it isn't legal advice. If a letter arrives, bring in regulatory counsel before you reply.

When the FTC signs the letter too

None of the 16 was a joint letter, but FDA and the FTC do write together, and a joint letter brings a second regulator with its own standard. In May 2021 they jointly warned a seller of fertility supplements (the letter), one of five joint letters on fertility supplements that FDA announced that month (FDA). FDA's part cited unapproved new drugs. The FTC's part said it's unlawful to advertise that a product can prevent, treat or cure human disease unless the firm has "a reasonable basis consisting of competent and reliable scientific evidence", including, when appropriate, well-controlled human clinical studies. Both agencies asked for a reply within 15 working days.

A September 2021 joint letter, about a product with a disease in its name, has the line every supplement copywriter should keep in mind: the FTC wrote that such claims can be made "through the use of a product name, website name, metatags, or other means" (the letter). FDA's part of that letter quoted the firm's website, its Facebook page and its Amazon storefront, the only marketplace listing in any letter we read. On fda.gov, a joint letter lists the Federal Trade Commission in its issuing office and carries a second signature, from the FTC's Division of Advertising Practices. What the FTC accepts as competent and reliable evidence is covered in our post on supplement advertising rules.

Audit your VSL page before FDA reads it

The sample says where to start: your own site, every page of it, then everything that repeats it. Work through this list with the script, the label and your post history open:

Before FDA reads your page: a self-audit

• List every place your claims live: product pages, the VSL script and its on-screen text, about and FAQ pages, the blog, emails, ads, labels and every social account
• Read the old material too, posts from years ago included, and fix or remove anything that makes a disease claim
• Mark every line that names a disease or describes its symptoms, its treatment or its prevention, in product names as well as in the copy
• Pull testimonials and comments that report a disease result, on the page, in the video and on social media
• Check that the label, the page and the ads make the same claims, with the same disclaimer
• Confirm the status of every ingredient: no new dietary ingredient without the notification it needs, no drug ingredient
• Ask your manufacturer for its latest FDA inspection results and how it answered them
• Search FDA's warning letters for your ingredients, your kind of product and your manufacturer
• Decide who opens mail from FDA and who can sign a reply within 15 working days

0 of 9 done

On a RevvyScales page, the theme editor lists the page's parts in the order they appear, from the top of the page to the legal footer, so you can review the page one block at a time (theme editor). For the claim rules across the rest of a VSL, testimonials and disclosures included, see the VSL compliance guide.