Peptides for weight loss: what’s approved and what isn’t

The peptides with strong evidence for weight loss are prescription GLP-1 medicines: Wegovy (semaglutide), Zepbound (tirzepatide) and Saxenda (liraglutide), each FDA-approved for long-term weight management alongside a reduced-calorie diet and more physical activity. Newer drugs such as retatrutide and CagriSema are still in trials, and peptides sold online for “fat loss” are unapproved, with evidence that is mostly from animals.

Which peptides are FDA-approved for weight loss?

Sources: Wegovy, Zepbound and Saxenda prescribing information.

Their labels also cover other uses. Wegovy is approved to lower the risk of heart attack, stroke and cardiovascular death in adults with heart disease and excess weight, and the injection treats a form of fatty liver disease (MASH). Zepbound is approved for moderate to severe obstructive sleep apnea in adults with obesity.

In the trials behind these approvals, adults on semaglutide lost an average of 14.9% of body weight over 68 weeks, against 2.4% on placebo (STEP 1). On tirzepatide, average weight change over 72 weeks was −15.0% to −20.9% across the doses tested, against −3.1% on placebo (SURMOUNT-1). These are averages: some people lose much more, some much less.

The 2026 approval of Foundayo (orforglipron), a daily tablet for weight management, added an option that is not a peptide: it is a small molecule that acts on the GLP-1 receptor (Foundayo label; Wharton et al., 2025).

How do GLP-1 peptides cause weight loss?

GLP-1 is a gut hormone. Medicines that act on its receptor slow how fast the stomach empties and reduce food intake, as well as increasing insulin and lowering glucagon after meals (Drucker, 2018). Tirzepatide also activates the receptor for a second gut hormone, GIP (Zepbound label). Natural GLP-1 is broken down within minutes, so these medicines are modified to last for a day or a week (Saxenda label).

What about retatrutide and CagriSema?

Both are investigational: promising in trials, but not FDA-approved for any use.

• Retatrutide (Eli Lilly) acts on GIP, GLP-1 and glucagon receptors. In the phase 3 TRIUMPH-1 trial of 2,339 adults with obesity but not diabetes, average weight change over 80 weeks was −17.6% to −25.0% across the doses tested, against −3.9% on placebo. The trial was funded by Eli Lilly (Jastreboff et al., 2026).
• CagriSema combines cagrilintide, a long-acting version of the hormone amylin, with semaglutide. In the 68-week REDEFINE 1 trial, average weight change was −20.4%, against −3.0% on placebo, and 79.6% of people on it had digestive side effects, against 39.9% on placebo (Garvey et al., 2025). Novo Nordisk asked the FDA to approve it in December 2025 (Novo Nordisk); it was not on the FDA’s list of 2026 novel drug approvals when we checked (FDA).

The FDA states that retatrutide and cagrilintide “cannot be used in compounding under federal law” and “have not been found safe and effective for any condition” (FDA). Vials sold online under these names are unapproved drugs.

US regulatory status

• RetatrutideUS status: Investigational

  Retatrutide is not approved by the FDA for any use and has no brand name. Eli Lilly published phase 3 trials in 2026, but no FDA filing or approval had been announced as of October 16, 2026. The FDA says retatrutide cannot be used in compounding, and it has warned telehealth companies, ingredient distributors and websites selling “research use only” retatrutide.

  As of October 16, 2026

  Sources9121321222324

• CagrilintideUS status: Investigational

  Neither cagrilintide nor CagriSema (cagrilintide with semaglutide) is FDA-approved. Novo Nordisk submitted CagriSema for weight management in December 2025 and expected a decision by late 2026; no approval had been announced as of October 16, 2026. The FDA says cagrilintide cannot be used in compounding, and it has warned a website selling it as a “research” peptide.

  As of October 16, 2026

  Sources111213252627

Is compounded semaglutide or tirzepatide the same thing?

No. Compounded drugs are not FDA-approved, so the FDA does not review them for safety, effectiveness or quality before they are sold (FDA).

While a drug is on the FDA’s shortage list, pharmacies have more room to compound copies of it. The FDA declared the tirzepatide shortage resolved in December 2024 and the semaglutide shortage resolved in February 2025, and the grace periods for compounders ended during 2025. Since then, compounders face legal limits on making copies of the approved products (FDA). In April 2026 the FDA also proposed keeping semaglutide, tirzepatide and liraglutide off the list of ingredients outsourcing facilities may compound from (FDA).

The FDA has flagged specific problems with compounded versions:

• Adverse event reports. As of May 31, 2026, it had received 990 reports for compounded semaglutide and more than 730 for compounded tirzepatide, and says these are likely underreported.
• Dosing errors. Some reports, including hospitalizations, may be linked to people measuring the wrong amount, or to doses above those on the FDA label.
• Salt forms. Some compounded “semaglutide” is semaglutide sodium or acetate, which are different active ingredients from the approved drug.

All three are from the FDA’s page on unapproved GLP-1 drugs (FDA). The FDA also recommends throwing away a multi-dose vial 28 days after first use. Our guide to how long mixed vials last covers storage.

US regulatory status

• SemaglutideUS status: FDA-approved

  Novo Nordisk makes every FDA-approved semaglutide product. Ozempic injection is approved for adults with type 2 diabetes to improve blood sugar, to lower the risk of major cardiovascular events in those with established cardiovascular disease, and to lower the risk of kidney function decline, kidney failure and cardiovascular death in those with chronic kidney disease. Rybelsus and Ozempic tablets share one label: once-daily tablets for adults with type 2 diabetes, to improve blood sugar and to lower the risk of major cardiovascular events in those at high risk, and they are not interchangeable mg for mg. Wegovy injection is approved for long-term weight reduction in adults and children 12 and older with obesity, and in adults with overweight and a weight-related condition; to lower the risk of cardiovascular death, heart attack and stroke in adults with cardiovascular disease and obesity or overweight (since March 2024); and, under accelerated approval since August 2025, for noncirrhotic MASH with moderate to advanced liver fibrosis in adults. Its 7.2 mg dose, Wegovy HD, was approved on March 19, 2026, for weight reduction in adults only. Wegovy tablets, approved on December 22, 2025, are for adults, for weight reduction and heart risk reduction, and are not approved for MASH or for children. Compounded semaglutide is not FDA-approved: the FDA declared the shortage resolved on February 21, 2025, its grace periods for compounders ended in 2025, and on April 30, 2026 it proposed excluding semaglutide from the list outsourcing facilities may compound from (no final decision as of this date). Salt forms such as semaglutide sodium and acetate are different active ingredients from the approved drugs, and the FDA has sent warning letters to sellers of semaglutide labeled “for research purposes” or “not for human consumption”.

  As of October 16, 2026

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• TirzepatideUS status: FDA-approved

  Eli Lilly makes both FDA-approved products: Mounjaro, for type 2 diabetes (adults and children 10 and older) and to lower heart risk in high-risk adults with type 2 diabetes, and Zepbound, for long-term weight management and for sleep apnea with obesity in adults. Compounded tirzepatide is not FDA-approved: the FDA declared the shortage resolved on December 19, 2024, and in April 2026 proposed excluding it from the list outsourcing facilities may compound from. The FDA has also warned sellers of “research use only” tirzepatide.

  As of October 16, 2026

  Sources21314152436

Peptides marketed for fat loss: what the evidence shows

Outside the GLP-1 medicines, the peptides promoted for fat loss rest on much thinner evidence. Grades below come from our compound pages.

• AOD-9604 is a fragment of human growth hormone. It reduced weight gain in obese rats (Ng et al., 2000) and was developed as an anti-obesity drug, but it was never approved; a 2026 review found that the short-term human trials gave limited interpretable signals (Dominikowski et al., 2026). The FDA notes serious adverse events that may be associated with it, though causality is not clear (FDA).
• MOTS-c prevented diet-induced obesity in mice (Lee et al., 2015). The FDA has not identified any human exposure data for it by any route.
• Tesamorelin is approved only for abdominal fat in adults with HIV and lipodystrophy. Its label says it “is not indicated for weight loss management as it has a weight neutral effect” (Egrifta WR label).

Sellers also use invented names for real drugs, such as “GLP-3” for retatrutide. The FDA has sent warning letters to websites selling GLP-1 look-alikes labeled “research use only”, and says such products are “of unknown quality and may be harmful” (FDA).

Side effects and safety

On the Zepbound label, the most common side effects are digestive: nausea, diarrhea, vomiting, constipation, abdominal pain and indigestion, along with injection-site reactions, tiredness and hair loss (Zepbound label). GLP-1 medicines carry a boxed warning about thyroid C-cell tumors seen in rodents, and their labels warn about pancreatitis and gallbladder disease, among other risks (Wegovy label). The semaglutide and tirzepatide pages list the label warnings in full.

For unapproved products, there is no label and often no reliable safety data at all. That uncertainty is itself the main risk.

Questions people ask