Compounded semaglutide and tirzepatide vs the brand products

For a couple of years, “compounded semaglutide” was everywhere. Telehealth ads, clinic websites, a vial and a box of syringes for a fraction of the list price of Wegovy. Then the offers started disappearing, and a lot of people were left holding a half-used vial and a fair question: what was that, exactly, and was it the same drug?

This guide sticks to what the FDA has actually published — how compounding works, the window when it was widely available, what closed that window, and what the agency says it has seen since. There is no verdict at the end. There is a list of things the FDA says are known, a shorter list of things it says are not known, and some questions worth asking.

What compounding actually is

Compounding is a pharmacy making a medicine rather than dispensing one a manufacturer made. It is a long-established part of US pharmacy, and the FDA’s own framing is narrow: “a compounded drug might be appropriate if a patient’s medical need cannot be met by an FDA-approved drug, or the FDA-approved drug is not commercially available”.

The bit that matters most is the regulatory status. In the agency’s words, “compounded drugs are not FDA approved. This means the agency does not review compounded drugs for safety, effectiveness or quality before they are marketed.” That is the structural difference from Wegovy or Zepbound, which went through a review of the trial data before they reached a pharmacy shelf.

There are also two different kinds of compounder, and they are not overseen the same way. Under section 503A, a licensed pharmacist compounding in a state-licensed pharmacy is overseen primarily by the state board of pharmacy, and the FDA notes these products are “not subject to current good manufacturing practice (CGMP) requirements”. Under section 503B, an outsourcing facility registers with the FDA, must meet CGMP standards, and is “primarily overseen by FDA and inspected by FDA according to a risk-based schedule”. Same word, two quite different levels of federal oversight.

The window — and how it closed

Compounders can generally make a copy of a commercially available drug when that drug is on the FDA’s shortage list. Semaglutide and tirzepatide were both on it, and that is the legal footing the compounded GLP-1 market stood on. When the shortages ended, the footing went with them.

The FDA determined the tirzepatide injection shortage resolved on 19 December 2024, and the semaglutide injection shortage resolved on 21 February 2025. Its statement puts the consequence simply: when a shortage is resolved, “FDA generally considers the drug to be commercially available”, and the restrictions on making essentially a copy of a commercially available drug apply again. The agency then set transition dates for semaglutide — 22 April 2025 for state-licensed pharmacies under 503A, and 22 May 2025 for outsourcing facilities under 503B.

Two later moves narrowed things further. In September 2025 the FDA launched a “green list” import alert aimed at stopping “potentially dangerous GLP-1 active pharmaceutical ingredients (APIs) from unverified foreign sources from entering the U.S. market”, with ingredients from other sources liable to be detained. Then on 30 April 2026 the agency proposed to exclude semaglutide, tirzepatide and liraglutide from the 503B bulks list, saying it “did not identify sufficient evidence” of clinical need — a list that matters because, in most cases, outsourcing facilities cannot compound from a bulk substance unless it is on that list or the drug is in shortage. Comments on the proposal were open until 29 June 2026.

What the FDA says it has seen

The agency publishes running counts of adverse event reports. As of 31 May 2026 it had received 990 reports for compounded semaglutide and more than 730 for compounded tirzepatide. It adds an important caveat about how to read those numbers: “federal law does not require state-licensed pharmacies that are not outsourcing facilities to submit adverse events to FDA so it is likely that adverse events from compounded versions of these drugs are underreported”. A report is also not proof the drug caused the event.

The clearest specific pattern is dosing errors. In a 2024 alert, the FDA described reports of patients who “administered five to 20 times more than the intended dose of semaglutide”, with reported effects including gastrointestinal symptoms, fainting, headache, migraine, dehydration, acute pancreatitis and gallstones. The mechanism was mundane and, in hindsight, predictable: the branded semaglutide injections come in pre-set pens, while compounded semaglutide often came in a vial. The FDA noted that “many of the patients who received vials of compounded semaglutide lacked experience with self-injections”, and that confusion between different units of measurement may have played a part.

Then there is the ingredient itself. Some compounders used salt forms — semaglutide sodium and semaglutide acetate — rather than the base form in the approved products. The FDA’s position is that “the agency does not have information on whether these salts have the same chemical and pharmacologic properties”. Separately, it warns about counterfeit products, which may “contain the wrong ingredients, contain too little, too much or no active ingredient at all or other harmful ingredients, and are illegal”.

What is not known

This is the part that tends to get skipped. Everything published about how much weight people lost on semaglutide or tirzepatide comes from trials of the approved products — you can see the trial list behind every number on this site under clinical evidence. Those trials tested a specific molecule at a specific purity in a specific delivery device. A compounded preparation has not been through that, and the FDA is explicit that it does not review compounded drugs for safety, effectiveness or quality before they are marketed.

So the honest position is that nobody — the compounder included — can point to trial data for a compounded version, because none exists. And where a salt form was used instead of the base form, the FDA says it does not have information on whether the chemical and pharmacologic properties match. That is not the same as saying they differ. It means the question is open.

Questions worth asking a pharmacy or clinic

If you are being offered a compounded GLP-1 today, or you are trying to work out what you were taking before, these are the questions that get you to a factual answer. The FDA’s own advice to patients is short: get a prescription from your doctor, and fill it at a state-licensed pharmacy.

None of this settles what anyone should do, and it is not meant to. It is the paper trail: what compounding is, when it was widely available and why that changed, what the FDA has recorded, and where the gaps in the evidence sit. The decision itself belongs in a conversation with a prescriber — the talk to your doctor page has a list you can take in with you.