FDA Warning Letters to Peptide Websites: What the 2025 to 2026 Letters Cite

This guide is for people who run research-use-only stores and for the people who design, build and edit their websites. Between December 2025 and August 2026, FDA published a series of warning letters to sellers of research peptides. The letters are useful to read because they describe, in the agency's own terms, which parts of a website it relied on. We summarize what they cite, explain why the research-use-only label did not settle the question and finish with a review checklist. We do not repeat any claim wording from the letters, and we do not name products.

If you want the short commercial version of this page, with the controls we build into a store, read our compliance-first peptide website page. This guide is the longer explanation behind it.

Timeline of the 2025 to 2026 letters

This guide covers three rounds of published letters, from December 2025 to August 2026. Each row links to the source we used. Read the sources themselves rather than relying on any summary, including ours.

Sources: the December 2025 FDA warning letter to Pinnacle Peptides, a summary of the seven March 2026 letters and a legal alert on the five August 2026 letters. We name only the seller in the FDA link title and no other sellers.

The pattern across the three rounds is consistent. Each letter looked at what the website said and offered, then asked what the whole presentation showed about intended use. The letters do not focus on one missing sentence or one badly placed disclaimer. They focus on the overall picture a visitor would form.

Why the research-use-only label didn't decide the outcome

Every round of letters addresses research-use-only labeling directly. In December 2025, FDA said that research-only and not-for-human-use labeling did not change its conclusion. The March 2026 letters made the same point about research-use and not-intended-for-human-consumption labels. The August 2026 commentary notes that every vendor in that round used a research-use disclaimer.

The reason is intended use. In plain terms, intended use is what a product is for, judged from the evidence around it rather than from a single label. That evidence includes what the seller says on product pages, what it publishes elsewhere on the site, what it sells together and how it talks to buyers. A label that says one thing does not cancel the rest of the site if the rest of the site says another.

The August 2026 commentary describes this as net impression: FDA evaluated each website as a whole. A practical way to think about it is to imagine a reader who sees every page, every product listing, every bundle in the cart and every linked channel, then asks what the business is offering and to whom. The disclaimer is one item in that reading, not the deciding one.

This is why a review that only checks the footer, or only checks product descriptions, leaves gaps. The elements below are where the letters found the evidence.

The website elements the letters cite

Each subsection below covers one element, what the sources say about it and what a review should look at. We describe categories only. We do not reproduce or paraphrase the cited wording.

Product-page claims

All three rounds cite claims on product pages. The December 2025 letter quoted disease and body-function claims from product pages. The March 2026 letters cite therapeutic claims, and the August 2026 letters cite disease or body-function claims. In short, the product page was where the agency found the clearest statements about what a product was for.

For a review, this means reading every product description, short description, bullet list, image caption, badge and FAQ on each product page. Claims also hide in places teams forget: variant names, comparison charts, review snippets that are shown on the page and promotional banners. Copy describing identity, documentation and research-use status is a different kind of content from copy describing effects in a body.

Dosing and how-to content

The August 2026 letters cite dosing guidance. Dosing content tells a reader how much of something to use and how often, which points to use in a person or animal rather than in a laboratory. It can appear as a dedicated page, a section on a product page, a downloadable guide, a blog post or an answer in a help center.

A review should search the whole site, including the blog, help pages, emails and downloadable files, for dosing and administration content. It should also check content created by others but shown on your site, such as reviews and questions from buyers.

Calculators

One August 2026 letter cites a peptide calculator as a means to prepare an injectable drug. A calculator is a tool rather than a sentence, so it is easy to miss in a copy review. It can still say a great deal about intended use, because of what it helps a visitor do.

Review every interactive tool on the site, what it calculates and what it implies about how a product will be used. Treat embedded widgets and linked third-party tools the same way as tools you built.

Bundled supplies in the cart

The March 2026 letters cite bacteriostatic water sold alongside the peptides, which was treated as showing injection use. The August 2026 letters cite bacteriostatic water sold alongside injectable products. Here, the catalog itself was evidence, not just the words describing it.

This element cannot be fixed by editing copy. It is a decision about what the business sells and how it presents products together: in bundles, in cart offers, in related-product blocks and in collections. Bring the full catalog and every cross-sell rule to counsel.

Code-name labels

The March 2026 letters cite code-name product labels. A naming scheme does not remove a product's identity when the rest of the site makes clear what it is. Review product names, abbreviations, SKUs that appear on the storefront and the way names are explained on other pages.

Community forums and off-site channels

One seller in the March 2026 round offered a community forum, which the letters cite. The same summary notes some listings on a marketplace. Content in a forum, group or marketplace listing connected to the business can form part of the overall picture, even when the main website is careful.

A review should list every channel the business runs or links to: forums, chat groups, social profiles, marketplace listings, email newsletters and affiliate pages. Each one needs the same review as the storefront.

Is a research use only disclaimer enough?

On its own, no. That is the clearest lesson from the letters. In December 2025, FDA said research-only and not-for-human-use labeling did not change its conclusion. The March 2026 letters said research-use and not-intended-for-human-consumption labels did not change intended use. In August 2026, every vendor used a research-use disclaimer, and FDA evaluated each site as a whole.

A disclaimer still has a job. It states the business's policy clearly at the points where a buyer makes decisions: the footer, the product page, the add-to-cart button, the cart and checkout. It works when the rest of the site is consistent with it. Our free RUO disclaimer generator drafts starting text for those places, for counsel to review. It is not a substitute for reviewing the rest of the site.

A review checklist for counsel and the team

Use this list to prepare a review session. It is a set of questions to bring to counsel, not a compliance standard. Work through it page by page, then channel by channel.

• List every page type on the site, including blog posts, help pages and landing pages
• Read every product page in full: descriptions, bullets, captions, badges, FAQs and variant names
• Search the whole site and downloadable files for dosing and administration content
• List every calculator, widget and interactive tool, and what each one helps a visitor do
• Export the full catalog and every bundle, cross-sell, cart offer and related-product rule
• Review how product names and abbreviations are presented and explained
• List every forum, group, social profile, marketplace listing and affiliate page tied to the business
• Review reviews, questions and other buyer content shown on the site
• Check every email template, popup and promo bar
• Check the footer, product, cart and checkout disclaimers for consistency with the rest of the site
• Decide who can publish copy, and how changes are reviewed and recorded
• Set a schedule to repeat the review and to check FDA's database for new letters

For a page-by-page version focused on disclaimers, checkout confirmations and imagery, see our RUO website compliance checklist.

How our platform supports the review

We build stores for research-use brands, so we built controls around the elements above. The copy checker runs in off, warn or block mode on products, pages, sections, header and footer, cart, popup, collections, emails and AI-agent edits. It flags dosing, injection, human-use framing, treatment, weight or fat-loss, muscle-building and anti-aging claims, plus approval-style claims. You can try a simplified version with our free RUO copy checker, which runs in your browser.

Research-use attestation and minimum age are stored on every order, with the attestation text and an age from 18 to 25 configurable. Disclaimers at add-to-cart, in the cart and in the footer are configurable. You can block the countries and US states you choose. See how these fit together in the platform's compliance tools.

The limit matters, so we state it plainly. Software helps a team keep copy in line with its own policy. It does not make a product lawful. Removing claims does not change what a business sells or how it sells it, and a checker cannot decide what belongs in your catalog, which channels you run or what your products are for. Those are decisions for the business and its counsel.

Check the database for new letters

This guide covers letters published through August 2026. FDA publishes new warning letters regularly, and later letters may cite elements not covered here. Search FDA's warning letters database for new letters before each review, and bring anything relevant to counsel. Policies, enforcement priorities and the elements cited can change, so treat any summary, including this one, as a starting point.