Compounded, branded or "research" tirzepatide: identity, purity and law side by side

The three supply chains side by side (as of October 2, 2026)

The rest of this page sets out where each row comes from.

Branded: Mounjaro and Zepbound

Tirzepatide High is approved in the US as Mounjaro for type 2 diabetes, since May 2022, and as Zepbound for weight management, since November 2023 ¹. Approval means the FDA reviewed the manufacturer's evidence and its manufacturing, and the product carries a label with its doses, warnings and interactions; the current Zepbound label, effective August 28, 2026, for example, tells users of oral contraceptives to switch to a non-oral method or add a barrier method for four weeks after starting and after each dose increase ².

Compounded tirzepatide

Pharmacies were allowed to make copies of tirzepatide while it was on the FDA's drug shortage list, from December 2022. On December 19, 2024, the FDA issued a declaratory order finding the shortage resolved and set end dates for its enforcement discretion: February 18, 2025 for state-licensed pharmacies compounding under section 503A, and March 19, 2025 for outsourcing facilities under section 503B ³. Since then, a 503A pharmacy may not compound what is essentially a copy of the commercially available drug; it can still compound tirzepatide in narrow cases, such as a documented clinical difference for an identified patient ⁴. A 503B facility needs the drug to be on the shortage list or on the 503B bulks list ⁴, and on May 1, 2026 the FDA proposed not to add tirzepatide, semaglutide or liraglutide to that list (91 FR 23431); at our last check on September 25, 2026, it had not published a final decision ⁵.

The FDA has also rejected the most common workaround. In a warning letter dated September 18, 2026, it told a large Houston compounding pharmacy that its tirzepatide with niacinamide appears to be essentially a copy of the approved drug, and that the volumes it made suggest the added vitamin was a pretext ⁶.

On safety, the evidence is a signal rather than a measurement. A study of the FDA's adverse event reporting system from 2018 to 2024 found 707 reports involving compounded GLP-1 drugs out of 81,078. Compared with branded products, compounded ones had higher reporting odds of preparation errors, contamination, manufacturing issues and hospitalization (odds ratio 2.35) ⁷. Reporting odds show which problems are reported more often, not how often they happen.

"Research" tirzepatide

The third channel sells tirzepatide powder in vials labelled "for research purposes only" or "not for human consumption", without a prescription. A 2024 commentary by pharmacy researchers notes that buyers often receive the vial without the supplies or knowledge needed to dissolve, draw up and inject it, and that skipping the prescriber removes the checks for interactions and monitoring ⁸.

The FDA does not accept the label at face value. Its warning letters dated August 24, 2026 to five online sellers named tirzepatide among the products, called them unapproved new drugs, and said the "research use only" and "not for human consumption" disclaimers did not outweigh what the sellers' own websites showed ⁹.

What is in such vials has rarely been tested independently. The one published test purchase of online GLP-1 vials we found concerns semaglutide, not tirzepatide: the three vials delivered held 28.6% to 38.7% more semaglutide than labelled, yet measured purity of only 7.7% to 14.4% against the 99% claimed, and endotoxin was found in every sample ¹⁰. A certificate of analysis supplied by a seller is not the same as a regulator's check; our COA Decoder explains what one can and cannot show.

What this means in practice

Branded tirzepatide is the only version whose contents the FDA has checked against an approved application. Compounded tirzepatide may still be prescribed in limited cases, but the legal room has narrowed every year since the shortage ended, and the FDA's proposal on the 503B list is still pending. "Research" tirzepatide has no route to legitimacy as a medicine; the FDA's actions so far have been aimed at the sellers and pharmacies, and the risk of what is in the vial falls on the person who injects it. For anyone losing access to a compounded GLP-1, our GLP-1 transition guide covers the options.

Frequently asked questions

Is compounded tirzepatide still legal?

Only in narrow cases. Since the FDA found the shortage resolved on December 19, 2024, pharmacies may not compound copies of the approved drug; the grace periods ended on February 18, 2025 (503A) and March 19, 2025 (503B). A 503A pharmacy can still compound it for an identified patient with a documented clinical difference.

Is compounded tirzepatide the same as Zepbound?

It contains the same active ingredient but is not FDA-approved, and its identity and purity are checked by the pharmacy rather than against an approved application. The FDA said in September 2026 that adding a vitamin does not make a compounded copy legal.

Is research tirzepatide safe?

Nothing independent verifies what is in it. The FDA called such products unapproved new drugs in August 2026, and the one published test purchase of online GLP-1 vials, of semaglutide, found purity of 7.7% to 14.4% and endotoxin in every sample.

What is the 503B proposal?

On May 1, 2026, the FDA proposed not to add tirzepatide, semaglutide or liraglutide to the list of substances outsourcing facilities can compound from. Comments closed July 30, 2026; at our last check, the final decision had not been published.

Related on Grey Peptides

• Tirzepatide
• Losing compounded GLP-1 access
• The 2026 enforcement timeline

Sources

1. Grey Peptides dataset, tirzepatide record (Drugs@FDA approvals of Mounjaro, May 2022, and Zepbound, November 2023); read October 2, 2026.
2. Eli Lilly. Zepbound (tirzepatide) US prescribing information (openFDA set 487cd7e7-434c-4925-99fa-aa80b1cc776b, effective August 28, 2026); read October 2, 2026.
3. US FDA. Declaratory Order: Resolution of Shortages of Tirzepatide Injection Products (Mounjaro and Zepbound), December 19, 2024; read October 2, 2026. FDA
4. Frier Levitt. FDA Determines (Again) the Tirzepatide Shortage Is Resolved: What This Means for 503A and 503B Compounding; read October 2, 2026.
5. US FDA. FDA proposes to exclude semaglutide, tirzepatide and liraglutide from the 503B bulks list, May 1, 2026 (91 FR 23431); status as of September 25, 2026. FDA
6. US FDA. Warning letter to Empower Clinic Services LLC dba Empower Pharmacy, September 18, 2026; read October 2, 2026. FDA
7. McCall, K. L., et al. (2026). Safety analysis of compounded GLP-1 receptor agonists: a pharmacovigilance study using the FDA adverse event reporting system. Expert Opin Drug Saf, 25(3), 581-588. PMID: 40285721 · doi:10.1080/14740338.2025.2499670
8. Belcourt, J., et al. (2025). Bypassing Prescribers and Pharmacists: Online Purchasing of Semaglutide and Tirzepatide "For Research Purposes". Ann Pharmacother, 59(5), 485-490. PMID: 39285774 · doi:10.1177/10600280241277551
9. US FDA. Warning letters dated August 24, 2026 to five online peptide sellers, posted September 1, 2026 (one linked); read October 2, 2026. FDA
10. Ashraf, A. R., et al. (2024). Multifactor Quality and Safety Analysis of Semaglutide Products Sold by Online Sellers Without a Prescription: Market Surveillance, Content Analysis, and Product Purchase Evaluation Study. J Med Internet Res, 26, e65440. PMID: 39509151 · doi:10.2196/65440

Educational information, not medical advice. Each dose in this guide names its source, an approved label or a published study. None is a recommendation for you. An unapproved compound has no established safe or effective human dose, and products sold for “research use only” are not made or tested for people. Talk to a doctor before acting on anything on this site, including before you start, stop or change any medicine or dose.