What Cannot Legally Be Compounded — and Who Is Selling It Anyway

Not everything a compounding pharmacy can put in a vial is something it is allowed to put in a vial. The FDA has named specific molecules and specific chemical forms that cannot lawfully be used in compounding at all — and when we checked our own register against that list, 7 of the 560 sellers we track had one on their product menu.^[1] Here is what the rules actually say, and how to check a seller against them.

Retatrutide and cagrilintide: not eligible at all

The FDA’s position is unusually blunt, and worth reading in the agency’s own words rather than anyone’s summary of them:^[1]

Retatrutide and cagrilintide cannot be used in compounding under federal law. Additionally, these are not components of FDA-approved drugs and have not been found safe and effective for any condition.

— FDA, June 2026

Read that last clause carefully, because it is stronger than the one people expect. This is not “approved for diabetes but used off-label for weight”, which describes a great deal of ordinary prescribing. It is not approved for anything. There is no indication, anywhere, for which either molecule is an approved treatment.

The agency has acted on this in three directions at once, which is a useful signal of how seriously it takes it. It has warned telehealth companies for marketing unapproved drugs such as retatrutide, including marketing straight to consumers; it has warned the active-ingredient distributors selling retatrutide and other GLP-1 drugs to compounders; and it has warned outsourcing facilities for repackaging it.^[1]

What we found in our own register

We checked all 560 sellers we track. Seven have retatrutide on the product menu we hold for them. That number is the reason this article exists, but it is not the uncomfortable part — the uncomfortable part is what our own pages were saying about it, which was nothing.

Not one of those seven reviews told a reader that retatrutide cannot lawfully be compounded. Two came closest, and what they actually said was that the seller’s retatrutide “is compounded rather than FDA-approved, so it has not been reviewed by the agency” — true of every compounded product on this site, and a materially weaker statement than the one the FDA makes about this particular molecule. The other five said nothing at all.

That has been fixed at the place it renders. Every seller whose menu we hold now carries a specific warning naming the FDA’s position, and an automated check keeps it there. We have written before about how to verify a seller; this is the same discipline turned on ourselves, and it took two attempts — the first pass corrected a stored field that our own pages never publish, which warned precisely nobody.

Some of them are invisible to a search for the word. One sells it as “MR-3”; another files it as “Sema, tirz, reta”.

That is the finding worth carrying away from this, and it generalizes well beyond us. Searching a seller’s site for a molecule name does not tell you what the seller stocks. Abbreviations and in-house code names are common in this corner of the market, and they defeat the obvious check completely.

Salt forms are a different active ingredient

This one is subtler and easier to miss, and we have covered it at length in compounded versus brand semaglutide. The short version: some compounders work from semaglutide salts rather than the base, and the FDA treats those as a different active ingredient from the one in the approved drugs, with no lawful basis for compounding that it is aware of.^[1]

The practical point for a buyer is that this almost never appears on a product page. It surfaces on a certificate of analysis, if you ask for one, and the presence of “sodium” or “acetate” after the drug name is the whole tell.

The research-use label is not a loophole

A whole gray market runs on vials marked “for research purposes” or “not for human consumption”. The FDA has warned companies that sold exactly these products — containing semaglutide, tirzepatide or retatrutide — directly to consumers for human use, complete with dosing instructions.^[1]

The wording on the label is a legal posture, not a description of the product or of what the seller expects you to do with it. What you actually have is a substance of unknown quality with no one accountable for what is in it.

How to check a seller in five minutes

1. Read the full product menu, not the GLP-1 page. The molecule that cannot be compounded is rarely on the page you landed on; it is usually under peptides, add-ons, or a members-only list.
2. Watch for abbreviations and code names. “Reta”, “triple agonist”, “MR-3” and similar all point at the same molecule and none of them match a search for it.
3. Ask what chemical form the semaglutide is. Base, or a salt. If the answer names sodium or acetate, that is the FDA’s stated concern, verbatim.
4. Check who compounded it. FDA has seen labels naming pharmacies that do not exist, and labels naming real pharmacies that did not make the product.^[1]
5. Look at the shipment when it lands. Warm box, melted or missing ice packs: FDA’s advice is not to use it.^[1]