Compounded semaglutide and tirzepatide: what the FDA says and what testing found

What is a compounded GLP-1?

Compounding means a pharmacy mixes a drug itself instead of dispensing a factory-made product. It exists for real needs, such as a patient who cannot take an ingredient in the approved version. Compounded semaglutide and tirzepatide are usually sold as vials of liquid you draw up with a syringe, sometimes mixed with other ingredients.

The approved products are different. Semaglutide is sold as Wegovy and Ozempic (injections) and Rybelsus (tablets). Tirzepatide is sold as Zepbound and Mounjaro. These were tested in large randomized trials and are made under FDA-reviewed standards. For how the approved versions compare, see semaglutide vs tirzepatide and Ozempic vs Wegovy vs Mounjaro vs Zepbound.

Are compounded semaglutide and tirzepatide FDA-approved?

No. In its page on unapproved GLP-1 drugs, 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.¹ That does not mean every compounded product is bad. It means nobody outside the pharmacy has checked that a given vial contains what the label says, at the strength it says, without harmful impurities.

The shortages are over: key dates

During a national shortage, US law lets pharmacies make copies of the scarce drug. Once the FDA says a shortage is resolved, that permission goes away after a wind-down period. Licensed compounding pharmacies are called 503A pharmacies. Larger facilities that make batches are called 503B outsourcing facilities.²

In its April 1, 2026 update, the FDA said neither drug is on its shortage list or on the list of bulk substances that outsourcing facilities may use.² A 503A pharmacy can still compound a version when a prescriber documents that a change makes a significant difference for an identified patient. The FDA treats products with the same ingredient in a similar strength and route as "essentially a copy" of the approved drug.² That is why, as a 2026 review notes, many compounded products now come with added ingredients or a different form.⁶

What safety problems has the FDA reported?

The FDA says these counts are probably too low, because state-licensed pharmacies that are not outsourcing facilities do not have to report adverse events to the agency.¹ Reports like these show that problems happened. They cannot show how often problems happen, or prove the product caused them.

Dosing errors

Approved semaglutide comes in prefilled pens dosed in milligrams. Compounded versions come in different vials and concentrations. In July 2024 the FDA warned about overdoses with compounded semaglutide in multi-dose vials. Some people took 5 to 20 times the intended dose. Causes included confusion between milliliters, milligrams and syringe "units," syringes much larger than the dose, and prescribers miscalculating when converting milligrams to units. Reported effects included nausea, vomiting, stomach pain, fainting, headache, dehydration, acute pancreatitis and gallstones. Some people were hospitalized.³

A US poison control center described 3 similar cases in 2023. Two people injected 10 times their dose, and symptoms lasted for days.⁴ For what these stomach effects look like at normal doses, see GLP-1 nausea and stomach side effects.

Salt forms: semaglutide sodium and acetate

The FDA says some compounders have used semaglutide sodium or semaglutide acetate. It calls these different active ingredients from the one in the approved drugs. It says it does not know whether they act the same way, and it is not aware of any lawful basis for compounding with them.¹

What did independent testing find?

Few studies have tested compounded GLP-1 products directly, and the ones that exist are small. Keep in mind who sold each product.

• Illegal online sellers (JAMA Network Open, 2024). This is not the same as a licensed compounding pharmacy. Researchers ordered semaglutide from 6 websites selling it without a prescription. Only 3 products arrived; the other 3 sites were scams. All 3 vials contained semaglutide, but at 7% to 14% purity instead of the 99% claimed, and with 29% to 39% more semaglutide than labeled. One sample had high endotoxin levels, a sign of possible contamination.⁵
• Compounding pharmacy websites (Annals of Pharmacotherapy, 2026). Searching in early 2025, researchers found 33 compounded semaglutide or tirzepatide products that differed from approved ones. 48% added ingredients such as B12 (cyanocobalamin), glycine, niacinamide, docusate or ondansetron. Only 18% listed a beyond-use date and storage conditions. The authors found little justification for adding nutrients and called efficacy and safety largely unknown.⁶
• Tirzepatide with B12 (Expert Opinion on Drug Safety, 2026). Scientists at Eli Lilly, which makes Zepbound and Mounjaro, tested compounded tirzepatide-B12 products and reported a new impurity formed by a reaction between tirzepatide and some forms of B12. They say its clinical effects are unknown. Note that the authors work for the company that sells the approved drug.⁷

Compounded tirzepatide vs Zepbound: is there any comparison?

We found no randomized trial comparing a compounded semaglutide or tirzepatide product with Wegovy, Ozempic, Zepbound or Mounjaro. The weight-loss numbers you see quoted for these medicines come from trials of the approved products. See GLP-1 weight loss results for those figures. Whether a compounded product matches them depends on what is actually in the vial, which is the part the FDA does not check.

What to do if you use a compounded GLP-1

This article does not tell you to stop or switch. Those are decisions to make with a licensed prescriber, who can look at your situation, cost and options. Questions you may want to ask:

• Is my product made with semaglutide or tirzepatide base, or a salt form?
• Does it contain added ingredients, and why?
• Is my dose written in milligrams, and how many units or milliliters is that on my syringe?
• Is the pharmacy state-licensed, and is it a 503A pharmacy or a 503B facility?

If you get severe stomach pain, ongoing vomiting or signs of dehydration, get medical care promptly. The FDA asks patients and clinicians to report problems with compounded drugs to its MedWatch program.¹