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Home / Health / Peptides & GLP-1

Peptides and GLP-1 drugs: what the evidence shows, and what to watch out for

The strongest trial results, the side effects, the FDA warnings and the regulatory fight over research peptides, with dates and sources. Updated October 22, 2026.

Short answer: The approved GLP-1 medicines (semaglutide and tirzepatide) have large randomized trials behind them: average weight loss of roughly 15% to 21% in the headline studies, and a 20% lower rate of major heart events in one outcomes trial. They also carry real, well-documented side effects and some newer safety signals. The wider "peptide" market is different: products such as compounded GLP-1s and BPC-157 are not FDA-approved, FDA staff have said the evidence for BPC-157 is lacking, and a recent advisory-committee vote is not a final decision. General information only, not medical advice.

How strong is the evidence? A quick map

Not everything sold under the word "peptide" has the same evidence behind it. This is how the main categories compare as of October 22, 2026.

CategoryApproval statusEvidence qualityWhat to knowFDA-approved GLP-1 medicines (semaglutide, tirzepatide)Approved by FDAStrong: large randomized trials (STEP 1, SURMOUNT-1, SELECT)Real benefits and real side effects; prescribed and monitored by a clinicianCompounded semaglutide and tirzepatideNot FDA-approvedQuality and dosing vary by pharmacyFDA has received 990+ adverse event reports for compounded semaglutide and 730+ for tirzepatide (as of May 31, 2026)Products labeled "research use only" or "not for human consumption"Not approved; sold outside the legal pharmacy channelUnknown qualityFDA urges consumers not to buy themBPC-157 and similar peptidesNot FDA-approvedFDA staff said evidence of effectiveness is lackingAn advisory vote in July 2026 was not a final FDA decision

What the big GLP-1 trials found

Three published trials anchor the evidence. All three tested the approved drug at its approved dose, under medical supervision, alongside lifestyle support.

TrialWho and how longResultSTEP 1 (semaglutide 2.4 mg weekly), NEJM 20211,961 adults with obesity or overweight, no diabetes; 68 weeksAverage weight change of 14.9% versus 2.4% on placebo; 50.5% lost 15% or more versus 4.9%SURMOUNT-1 (tirzepatide weekly), NEJM 20222,539 adults with obesity or overweight; 72 weeksAt the 15 mg dose, 22.5% weight loss for people who stayed on the drug and 20.9% across everyone randomized, versus 2.4% to 3.1% on placeboSELECT (semaglutide 2.4 mg weekly), NEJM 202317,604 adults aged 45+ with overweight or obesity and existing heart disease, no diabetes; up to five years20% reduction in major adverse cardiovascular events (cardiovascular death, heart attack or stroke) versus placebo

The SURMOUNT-1 figure has two versions because the first counts the effect while people took the drug, and the second counts everyone assigned to treatment even if they stopped.

Source: STEP 1 abstract (Wilding et al., NEJM 2021) → Source: Lilly summary of SURMOUNT-1 (NEJM, June 4, 2022) → Source: American College of Cardiology on SELECT (Aug 10, 2023) →

The downsides: side effects and newer safety signals

Stomach side effects are common. In SURMOUNT-1, nausea affected 24.6% to 33.3% of people on tirzepatide versus 9.5% on placebo, diarrhea 18.7% to 23.0% versus 7.3%, and vomiting 8.3% to 12.2% versus 1.7%. About 4.3% to 7.1% stopped because of side effects, versus 2.6% on placebo. In STEP 1, 4.5% of people on semaglutide stopped because of stomach side effects versus 0.8% on placebo.

A rare eye condition is under study. A study of US veterans with type 2 diabetes, published in JAMA Ophthalmology on February 12, 2026, compared 11,478 people starting semaglutide with 90,883 starting an SGLT2 inhibitor. Non-arteritic anterior ischemic optic neuropathy (NAION) occurred at 123 per 100,000 person-years on semaglutide versus 67 on the comparison drugs, a hazard ratio of 2.33 after weighting (95% confidence interval 1.53 to 3.54). It is an observational study of one drug in one population, and the authors call the condition rare but serious. They recommend counseling patients and prompt evaluation of any vision symptoms.

The figures above come from published abstracts and press coverage of them; the full papers cover more outcomes, including rarer risks.

Source: Ophthalmology Times on the JAMA Ophthalmology study (Feb 18, 2026) →

Compounded and "research" GLP-1 products: what FDA warns about

FDA's page on unapproved GLP-1 drugs (current as of October 1, 2026) lists these concerns:

Dosing errors with compounded injectable semaglutide, some leading to hospitalization, from patients measuring doses wrong and from clinician miscalculations.
Counterfeit Ozempic found in the US supply, and fraudulent products with false labels naming pharmacies that did not make them.
Products labeled "for research purposes" or "not for human consumption" (semaglutide, tirzepatide, retatrutide and others) sold with human dosing instructions. FDA urges people not to buy them.
Retatrutide and cagrilintide cannot be used in compounding under federal law.
As of May 31, 2026: more than 990 adverse event reports for compounded semaglutide and more than 730 for compounded tirzepatide. FDA says these are likely underreported and cause is not always clear.

FDA's practical advice: compounded drugs should be used only when an approved drug cannot meet a patient's medical needs; get a prescription and fill it at a state-licensed pharmacy; discard multi-dose vials after 28 days; and be wary of deep discounts, no prescriber screening or products that look different from before.

Source: FDA, FDA's Concerns with Unapproved GLP-1 Drugs Used for Weight Loss (current as of Oct 1, 2026) →

BPC-157 and other research peptides: where regulation stands

April 15, 2026: According to a summary by the law firm Frier Levitt of an FDA notice, FDA announced its intent to remove 12 peptides, including BPC-157, TB-500 and GHK-Cu (injectable), from its "Category 2" list of bulk substances that raise significant safety concerns. The law firm stresses that removal is not approval and does not make these substances eligible for compounding.

July 23, 2026: FDA's Pharmacy Compounding Advisory Committee voted 8 to 6 with one abstention to recommend adding BPC-157 (for ulcerative colitis) and KPV to the list of substances pharmacies may compound. The vote is advisory, and FDA had not made a final decision when the report was published.

The evidence concerns raised at the meeting: FDA staff recommended against adding these peptides, citing a "lack of evidence to support the effectiveness of BPC-157" for ulcerative colitis. FDA officials described BPC-157 as "not well-characterized" and said quality standards could not be established. FDA reported three adverse event reports for BPC-157 (including one emergency room visit for shortness of breath) and said it was unclear whether the product caused them. The report also notes that several members FDA added to the panel in June have reported ties to prescribing or promoting peptides, which some FDA staff raised as a conflict-of-interest concern.

The takeaway: "Not on the do-not-compound list" and "recommended by an advisory panel" both fall short of "FDA-approved" or "proven to work".

Source: Frier Levitt law firm summary of the FDA notice (Apr 16, 2026) → Source: RAPS on the July 2026 advisory committee vote →

The industry behind it: a very large market

Eli Lilly's first-quarter 2026 results (reported May 1, 2026) show how large the category has become: revenue of $19.8 billion, up 56% from a year earlier; Mounjaro (tirzepatide for type 2 diabetes) at $8.7 billion, up 125%; Zepbound (tirzepatide for obesity) at $4.2 billion, up 80%; and full-year 2026 revenue guidance raised to $82 billion to $85 billion. Lilly's oral GLP-1 for weight loss, Foundayo (orforglipron), became broadly available in US pharmacies on April 9, 2026; Lilly did not disclose its sales.

Financial signal: demand is large enough that regulators, compounders, telehealth firms and counterfeiters are all pursuing it, which is why the safety warnings above matter. Company results are reported figures, not forecasts, and this is not investment advice.

Source: Pharmaceutical Technology on Lilly Q1 2026 (May 1, 2026, single source) →

Questions worth asking a clinician or pharmacist

Is an FDA-approved medicine available and appropriate for me, and why or why not?
If a compounded product is suggested, why can an approved one not meet my needs, and which state-licensed pharmacy makes it?
What side effects should I watch for, including vision changes, and when should I call?
How will we monitor my progress, and what is the plan if I stop?
For any peptide: is there human trial evidence for the condition I want to treat, or only animal and anecdotal reports?

Sources and limits: figures come from the sources linked above, checked October 22, 2026. Several items rest on a single report and are labeled as such. This page is general information, not medical advice. It does not recommend any product, dose or source. Talk to a licensed clinician before starting, changing or stopping any medicine. Report side effects or product problems to FDA MedWatch.

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