FDA warning letters to peptide sellers in 2026: what they cite

What happened

We searched the FDA's warning letters database on 23 September 2026 and found eleven letters issued in 2026 to online sellers of peptide products by the FDA's Center for Drug Evaluation and Research. Five were issued on 31 March, one on 17 June and five on 24 August. Each one says it follows a review of the seller's website. Each one finds that the products are unapproved new drugs.

We list them by FDA reference number. The companies are named on the FDA pages; we are interested in the pattern, not the sellers.

Each letter asks the seller to reply in writing within fifteen business or working days with the steps taken to correct the violations, and warns that failing to address them may lead to regulatory or legal action, including seizure and injunction.

The sentence every letter repeats

All eleven letters contain a version of the same footnote. The label wording changes from seller to seller. The conclusion does not. This is the version in letter 735063, dated 24 August 2026:

“Despite statements on your product labeling marketing your products ‘for research use only’ and ‘not for human or veterinary use,’ evidence obtained from your website establishes that your products are intended to be drugs for human use.”

Other letters quote labels such as “laboratory research purposes only”, “in vitro research and educational purposes only” and “for laboratory, research, and analytical use”. None of them changed the outcome. The label is one statement. The FDA reads it against everything else the seller publishes.

What the FDA used as evidence

The letters quote the sellers' own words at length. We will not repeat those quotes here, because most of them pair a product with a claim about the body. The categories are what matter.

Claims about disease or the body on product pages

Every letter quotes the seller's own pages, and most of the quotes describe effects on a condition or on how the body works. Under the FD&C Act, a product intended to treat or prevent disease, or to affect the structure or any function of the body, is a drug. The letters cite that definition and then point to the page.

Study summaries and mechanism explanations

Several letters quote short summaries of lab studies placed on the product page, and plain language explanations of how a compound acts on receptors. Framing a claim as “this study suggests” did not keep it out of the letter.

Hedged research wording

Letter 735127 quotes product pages written as lists of what a compound was “studied for”, “investigated for” and “explored for”. The FDA still treated them as evidence of intended human use. Careful verbs do not turn a benefit list into research copy.

Supplies sold next to the products

Ten of the eleven letters cite bacteriostatic water or a reconstitution kit offered alongside the peptides. Letter 735063 puts it this way in its footnote: the seller markets “bacteriostatic water as a solvent for reconstituting your products, thus, providing the means to prepare an injectable drug for human administration.” The water itself is then treated as a drug too.

Calculators, guides and communities

Letter 734884 cites a “peptide guide” and a “peptide calculator” offered with the water. Letter 721600 goes past the store: the FDA followed a link from the website to the seller's community forum and quoted downloadable cheat sheets that listed uses and dose schedules. What you publish around the store counts.

The FDA bulk substances safety list

Separate from the letters, the FDA keeps a page on bulk drug substances for compounding that may present significant safety risks (content current as of 22 April 2026). It names a number of peptides that are common in the research market, some in its category 2 table and others in a list of nominations that were withdrawn, each with the FDA's stated safety concern. If you sell anything on that page, read your entry. It is the FDA's public view of that compound.

What this means for your emails

None of the letters we read quotes an email. That is not a reason to relax. The regulation the letters rely on, 21 CFR 201.128, defines intended use broadly:

“This objective intent may, for example, be shown by labeling claims, advertising matter, or oral or written statements by such persons or their representatives.”

An email is a written statement and it is advertising. So the test the FDA applied to product pages is the test to apply to every send. In practice:

• Do not copy study summaries or benefit lists from old product pages into launch or restock emails.
• Do not send how-to content about preparing or measuring a product, and do not link to calculators or dose guides.
• Do not build offers that bundle products with water, syringes or other preparation supplies.
• Keep subject lines and preview text to the facts: product name, purity data, batch, availability, price.
• Read your automated flows, not only your campaigns. A welcome series written two years ago still sends every day.

Your email platform will not do this review for you. We cover the sending side on our email marketing for peptide brands page, and which platforms accept peptide brands at all in email platforms that allow peptides. If you were closed by Klaviyo, start with does Klaviyo allow peptide brands.

What this means for ads and landing pages

Ads send people to landing pages, and landing pages are part of your website. Everything above applies to them. Ad platforms also enforce their own rules on top of the law; we explain Meta's in Meta's restricted product policy, explained. For the wider picture across payments, stores and regulators, see the peptide brand compliance landscape for 2026.

A self-audit checklist

Set aside an afternoon and go through your own material with the letters open in another tab.

1. Read every product page the way the letters read them. Remove any sentence about a condition, a symptom or a change in the body.
2. Remove study summaries and mechanism explanations written for shoppers. Link to a certificate of analysis instead.
3. Look at what sits next to your products in the catalog, in bundles and in cross-sell blocks.
4. Check your calculators, guides, blog posts and downloads. Check any forum, group or community your site links to.
5. Export every active flow and every campaign from the last twelve months and read them with the same eye.
6. Write down what you changed and when. If you ever need to show your work, you will have it.

When the site and the emails describe a research product and nothing else, the label on the vial is no longer the only thing saying so. For plans and prices, see our pricing page.

This is general information, not legal advice.