Compounded semaglutide and tirzepatide: what is, and isn't, the same

What "compounded" actually means

Compounding is a long-standing pharmacy practice: a pharmacist mixes ingredients to produce a customised medication for an individual patient. It is legal, regulated, and useful in specific clinical situations, for example, when a patient is allergic to a dye in the commercial product, or needs a paediatric liquid version of a tablet medication.

Compounding was never intended for mass production of an off-the-shelf alternative to brand drugs.

While semaglutide and tirzepatide were on the FDA's shortage list, US compounding pharmacies were allowed to make their own versions. Many did, and many were sold online and through clinics at prices well below the brand drugs.

What the FDA has now decided

The FDA then declared both shortages resolved, and gave compounders a grace period to stop:

Since then, compounders cannot legally sell what are essentially copies of the approved medicines. Many now sell versions that differ, often by adding an ingredient such as vitamin B12 or niacinamide, and the FDA says a product with an added ingredient may still count as essentially a copy. (See tirzepatide or semaglutide with niacinamide or B12.)

Why the FDA cared

The agency's concerns, documented in public letters and warnings:

1. Salt forms. Some compounded products used semaglutide sodium or semaglutide acetate, chemically different from the semaglutide base used in Ozempic and Wegovy. Safety and effectiveness data for these salt forms do not exist.
2. Dosing errors. The FDA has received reports of adverse events, some needing hospital treatment, that may be linked to dosing errors with compounded injectable semaglutide. Compounded vials are not pre-filled pens: doses are drawn up with a syringe. By 31 May 2026, the FDA had received 990 adverse event reports linked to compounded semaglutide and more than 730 linked to compounded tirzepatide.
3. No review before sale. The FDA says compounded drugs are not FDA-approved, and that it does not review them for safety, effectiveness or quality before they are marketed.
4. Fakes. In the UK, the MHRA has warned of severe side effects from fake GLP-1 medicines and of counterfeit pens that closely copy the real ones.

The FDA's bottom line, paraphrased: compounded GLP-1s are not a different brand of the same drug. They are a different drug, with different testing, different manufacturing, and different risks.

What this means for you

For most people, the practical answer is straightforward: the FDA has declared the shortages over, and your prescriber is unlikely to recommend a compounded version.

If you have been on a compounded product, the most common transition is to the brand drug at the same equivalent dose. This is a prescriber's decision and may involve some titration. Talk to your prescriber before making any change.

"But it was the same molecule"

A common refrain, and one that needs careful unpacking.

The molecule with the same chemical name may or may not be the same physical product. Salt form matters. Concentration matters. Excipients (the non-active ingredients) matter. Sterility matters. Dose-accuracy matters.

A compounded "semaglutide" product that uses semaglutide sodium is not the same as Wegovy's semaglutide base. Whether the difference is clinically important is unsettled, because the dedicated studies have not been done. In a regulated drug approval, that gap would be unacceptable. In compounding, it has been tolerated.

This is the heart of the FDA's case for winding compounding down.

The cost question

The price advantage of compounded GLP-1s was substantial, and US cash prices for the brand drugs are high.

This is a real problem. The cost of GLP-1 medications in the United States, particularly for those without good insurance coverage, is a major access barrier. The end of large-scale compounding does not solve that problem.

What you can do:

• Check your insurance cover, and appeal a denial if your prescriber supports it.
• Ask about manufacturer programmes. In the US, Novo Nordisk (NovoCare) and Eli Lilly (LillyDirect) both offer savings and coverage support for their medicines.
• Talk to your prescriber about alternatives if cost is a real barrier, including other medicines in the class.
• In the UK, the MHRA says to buy only with a prescription after a consultation, and to check the pharmacy is on the General Pharmaceutical Council register.

What this is not

This is not a moral judgement of anyone who used compounded products during the shortage. The shortage was real, the prices of the brand drugs were prohibitive, and many people made a rational decision with the options they had. The situation has now changed; the options have changed; the right answer has changed.

What to do with this

The calculator takes a dose in milligrams, whatever the vial says on the label. For doses above the licensed range it applies the strongest published suppression factor rather than extrapolating past the evidence, and it says so.

Work out your numbers

Sources

1. US Food and Drug Administration. FDA clarifies policies for compounders as national GLP-1 supply begins to stabilize. fda.gov
2. US Food and Drug Administration. FDA's Concerns with Unapproved GLP-1 Drugs Used for Weight Loss. fda.gov
3. Medicines and Healthcare products Regulatory Agency. GLP-1 medicines for weight loss and diabetes: what you need to know. gov.uk
4. Novo Nordisk. NovoCare. novocare.com
5. Eli Lilly. LillyDirect. lillydirect.com

Medical disclaimer: Decisions about which medication to take, and from which source, are a conversation with your prescriber. See our full medical disclaimer.