Gray-Market GLP-1s: Semaglutide, Tirzepatide, Retatrutide

By Editorial team. Updated Oct 15, 2026. Awaiting expert review

This page summarizes public information from regulators and published research. It isn’t medical or legal advice, and it doesn’t describe how to use any product. If you’re considering a GLP-1 medicine, talk to a licensed clinician.

Semaglutide, tirzepatide and the experimental retatrutide are all sold online as “research chemicals” [1]. This guide explains how those products differ from approved and compounded medicines. It also sets out what regulators and researchers have found about them.

Three very different supply chains

1. Approved medicines. Semaglutide is sold as Ozempic and Wegovy, and tirzepatide as Mounjaro and Zepbound [3] [8] [10]. These products go through regulatory review and are dispensed on prescription [2] [3]. Even this channel has had counterfeits. The FDA has reported seizing counterfeit Ozempic from the US supply chain in December 2023 (thousands of units), April 2025 (several hundred) and December 2025 (dozens) [3]. In the 2023 case, the needles were counterfeit too, so their sterility couldn’t be confirmed [3]. In 2023 the EMA reported falsified Ozempic pens at wholesalers in the EU and UK [4]. The UK authorizes semaglutide (Wegovy), tirzepatide (Mounjaro) and liraglutide (Saxenda) for weight loss, to be taken only as prescribed [10].

2. Compounded versions. In the US, licensed pharmacies made copies of semaglutide and tirzepatide during national shortages [2]. The FDA declared the tirzepatide injection shortage resolved on December 19, 2024 and the semaglutide injection shortage resolved on February 21, 2025 [2]. Once a shortage ends, the FDA generally considers the drug commercially available, which limits compounding of copies [2]. Compounded products are not FDA-approved [1] [2]. As of May 31, 2026, the FDA had received 990 adverse-event reports for compounded semaglutide and more than 730 for compounded tirzepatide, and it says these numbers are likely underreported [1]. It has also received reports of adverse events, some needing hospital care, that may be related to dosing errors with compounded semaglutide injections, including patients measuring and self-administering incorrect doses [1]. The FDA also says it knows of no lawful basis for compounding with semaglutide salt forms (sodium or acetate) [1].

3. “Research use only” products. These are sold by websites that aren’t pharmacies, with labels saying the products are not for human use [1] [6] [7]. The FDA has warned companies selling semaglutide, tirzepatide, retatrutide, survodutide and mazdutide this way [1]. It says the products “have been sold directly to consumers for human use with dosing instructions”, and it advises consumers not to buy them [1].

Retatrutide: no approved version exists

Retatrutide is an experimental drug from Eli Lilly [8] [9]. Lilly says it plans to apply for FDA approval in the first quarter of 2027 [8], and no regulatory agency anywhere has approved retatrutide [9]. Under US federal law, retatrutide and cagrilintide cannot be used in compounding [1]. The MHRA says retatrutide is not authorized in the UK, so “anyone selling this product is doing so illegally” [10]. It adds that there’s no guarantee such products even contain retatrutide [10]. Every retatrutide vial sold online is therefore outside the regulated supply chain.

Research sellers often rename these compounds. In FDA warning letters, products appear as “RETA”, “GLP-3 RT (Retatrutide)”, “GLP-2 Tirz” and “GLP-1 Sema” [6] [7].

What testing has found

One 2024 study tracked online sellers of semaglutide and made test purchases from the six illegal online pharmacies with the most links [5]. It found:

• Three vial orders arrived. None of the three pen orders did; the researchers attribute this to non-delivery scams [5].
• Semaglutide content was 28.56–38.69% above the label amount [5].
• Measured purity was 7.7–14.37%, against the 99% claimed on the labels [5].
• No live microorganisms were found, but endotoxin was detected in every sample, at 2.1645 to 8.9511 EU/mg [5].

The sample was small and covered online pharmacies rather than research-chemical vendors, so it doesn’t describe the whole market. It does show how a product can fail on several measures at once while carrying a “99%” label. Our guide to peptide testing explains each measurement.

Enforcement is accelerating

• FDA warning letters. FDA warning letters to sellers of research-labeled GLP-1s, including letters in December 2024 and August 2026, rejected the “research use only” label as a defense [6] [7]. The full list is on our alerts page.
• Manufacturer lawsuits. In August 2026, Eli Lilly sued six companies over retatrutide sales, alleging that several presented their products as “research use only” while selling to consumers [8].
• UK raids. In October 2025, the MHRA dismantled what it described as the UK’s first illicit weight-loss medicine production facility [11]. It seized more than 2,000 unlicensed retatrutide and tirzepatide pens awaiting dispatch [11].
• Australia. In August 2026, the TGA seized peptide products, including retatrutide, from two premises allegedly linked to a social media influencer [12].
• Canada. Health Canada advisories about seized products have listed retatrutide and tirzepatide [13].

We log each action on our alerts page.

Lowering the risk

If you are thinking about a GLP-1 medicine, regulators give the same advice:

• Get a prescription from a licensed clinician [1] [10].
• Use a licensed pharmacy. In the US, the FDA says an online pharmacy is likely safe if it always requires a prescription, is licensed with a state board of pharmacy and has a licensed pharmacist available [14]. Deep discounts are a warning sign [14]. In the UK, check that the pharmacy is registered with the General Pharmaceutical Council [10].
• Walk away from offers without a prescription. The MHRA puts it simply: “if you’re offered a GLP-1 medicines without the need for a prescription – walk away” [10].
• Inspect what arrives. Report suspected counterfeits and side effects to your national regulator (in the US, MedWatch) [3].

How we cover GLP-1 vendors

We track GLP-1 offers on our price index because buyers are already in this market and accurate information is better than marketing claims. We haven’t published lab tests of our own yet; when we do, they will appear on our lab testing page. Coverage isn’t endorsement, and we don’t publish dosing or usage guidance. For the legal position by country, see research peptide legal status.