Is semaglutide an approved medicine?

The substance is the active ingredient of medicines authorised in the EU and elsewhere. Material supplied here is not one of those products: it has not been manufactured, tested, labelled or released under a marketing authorisation, and it is supplied as laboratory reagent for in-vitro research only.

What does the research on semaglutide report?

In STEP 1, mean body weight change of −14.9% over 68 weeks versus −2.4% on placebo. In SELECT, a primary cardiovascular endpoint event in 6.5% versus 8.0% on placebo across 17,604 patients. Both are results in named randomised trials of the authorised pharmaceutical product.

What happens when semaglutide is stopped?

The STEP 1 trial extension followed participants for a year after withdrawal and reported that roughly two-thirds of the lost weight returned, with cardiometabolic variables moving back in step. The trial authors concluded that continued treatment appears necessary to maintain the changes.

What are the reported adverse effects?

In SELECT, adverse events leading to permanent discontinuation occurred in 16.6% of the semaglutide group against 8.2% on placebo. Separately, observational work has reported a higher rate of non-arteritic anterior ischaemic optic neuropathy among patients prescribed the compound; that is observational and has not been tested in a trial designed for the question.

Is research-grade semaglutide the same as the prescription product?

No, and the difference is the point. The authorised product is made and released under a marketing authorisation against a pharmacopoeial specification. A research vial has a certificate of analysis and nothing else, and no published trial has studied material of that kind.

Research guides

Semaglutide: what the research says

A GLP-1 receptor agonist and the active ingredient of EU-authorised medicines. What the trials reported, the discontinuation rates, and the open questions.

Available in the catalogue

Supplied as research material. Sizes and pricing are on the product page. Availability is not a statement about what a compound does.

SEMAGLUTIDE
Metabolic & GLP-1

Semaglutide is the opposite of most compounds described in this section. Where the usual problem is too little human evidence, here there is a great deal of it — tens of thousands of participants across randomised trials published in the highest-profile medical journals. The difficulty is a different one, and it needs stating before any result.

The authorisation distinction, first

Semaglutide is the active ingredient of medicines authorised in the EU and elsewhere. Those products are manufactured under a marketing authorisation, tested and released against a pharmacopoeial specification, labelled with approved product information, and supplied through pharmacies on prescription.

A research vial is not that. It has not been manufactured, tested, labelled or released under any marketing authorisation, and it is supplied here as laboratory reagent for in-vitro research. Every trial described below studied the authorised pharmaceutical product. **No published trial has studied research-grade or compounded material**, and results from one do not transfer to the other — that is not a technicality about paperwork, it is the difference between a characterised medicinal product and a reagent with a certificate of analysis.

What the molecule is

A modified 31-amino-acid analogue of human GLP-1, engineered for a long plasma half-life. It activates the GLP-1 receptor, which drives glucose-dependent insulin secretion, slows gastric emptying, and acts on hypothalamic circuits involved in appetite regulation.

Three trials worth knowing apart

The literature is often summarised as one finding. It is at least three, asking different questions of different populations, and they are worth keeping separate.

STEP 1 asked what happens to body weight in adults with overweight or obesity and no diabetes, over 68 weeks, alongside lifestyle intervention.
SUSTAIN-6 asked whether cardiovascular events changed in patients with type 2 diabetes at high cardiovascular risk. It was designed as a safety trial rather than an efficacy one.
SELECT asked the cardiovascular question in a population with established cardiovascular disease and overweight or obesity but without diabetes — 17,604 patients, mean follow-up just under three and a half years.

The trial names matter because they are how the evidence is indexed. A claim sourced to "a study" without naming which one is usually reporting STEP 1's weight figure as though it answered the cardiovascular question, or the reverse.

What stopping did

The STEP 1 trial extension followed participants after treatment was withdrawn, and it is the most useful single result in this literature for understanding what the compound does and does not establish. One year after withdrawal, participants had regained roughly two-thirds of the weight they had lost, with cardiometabolic variables moving back in step. The authors' own conclusion was that continued treatment appears to be required to maintain the changes.

That finding is not a footnote to the efficacy result. It is the context that makes the efficacy result interpretable, and it is routinely left out of summaries.

What studies reported

Each entry states what a study examined and the model it used. Nothing below describes an outcome for a person.

Everything below is drawn from published research, and each entry names the model the study used. Approval status varies by compound and by country, and nothing described here is supplied as a medicine or for use in a person.

Wilding et al. (2021)New England Journal of Medicine · 384(11):989–1002
Reported mean body weight change of −14.9% over 68 weeks versus −2.4% on placebo, alongside lifestyle intervention, in adults with overweight or obesity and without diabetes.
human, randomised double-blind placebo-controlled (STEP 1) Source
Marso et al. (2016)New England Journal of Medicine · 375(19):1834–44
Assessed cardiovascular outcomes in patients with type 2 diabetes at high cardiovascular risk, reporting a lower rate of the composite cardiovascular endpoint than placebo over 104 weeks.
human, randomised double-blind placebo-controlled (SUSTAIN-6) Source
Lincoff et al. (2023)New England Journal of Medicine · 389(24):2221–32
In patients with pre-existing cardiovascular disease and overweight or obesity but without diabetes, reported a primary cardiovascular endpoint event in 6.5% versus 8.0% on placebo (hazard ratio 0.80) over a mean follow-up of 39.8 months.
human, randomised double-blind placebo-controlled, 17,604 patients (SELECT) Source

Adverse and null findings reported

Harms, tolerability observations, and trials that did not meet their endpoint. A negative result is a finding and is listed here rather than omitted.

Lincoff et al. (2023)New England Journal of Medicine · 389(24):2221–32
In the same trial, adverse events leading to permanent discontinuation of the trial product occurred in 16.6% of the semaglutide group versus 8.2% of the placebo group — twice the rate, in the largest and longest trial of the compound.
human, randomised double-blind placebo-controlled, 17,604 patients (SELECT) Source
Wilding et al. (2022)Diabetes, Obesity and Metabolism · 24(8):1553–64
Followed participants for one year after treatment withdrawal. Reported that roughly two-thirds of lost weight was regained, with cardiometabolic variables reverting in step, leaving a net change of −5.6% versus −0.1% on placebo.
human, STEP 1 trial extension, 327 participants Source
Hathaway et al. (2024)JAMA Ophthalmology · 142(8):732–9
Examined the rate of non-arteritic anterior ischaemic optic neuropathy among patients prescribed semaglutide compared with other agents, reporting a higher hazard. Observational and hypothesis-generating rather than causal.
human, retrospective observational cohort Source

What the research does not establish

An absence cannot be cited, so these are stated plainly. They are the part of the picture that silence would otherwise hide.

No published trial has studied research-grade or compounded semaglutide. Every result above was obtained with the authorised pharmaceutical product, and nothing in that literature characterises material supplied as a reagent.
The trials establish what happens during treatment. The STEP 1 extension is the only published answer to what happens after it, and that answer is substantial regain within a year.
Body composition is not fully characterised over long periods. What proportion of the weight lost is lean mass, and what that means over years rather than months, is not settled by the published trials.
Rodent carcinogenicity findings underlie warnings in the approved product information in several jurisdictions. Whether those findings translate to humans is not established, and no trial to date has been long enough to answer it.
The optic neuropathy signal comes from observational data. It has not been tested in a randomised trial designed to answer that question, so it is neither established nor dismissed.

Common questions

Is semaglutide an approved medicine?: The substance is the active ingredient of medicines authorised in the EU and elsewhere. Material supplied here is not one of those products: it has not been manufactured, tested, labelled or released under a marketing authorisation, and it is supplied as laboratory reagent for in-vitro research only.
What does the research on semaglutide report?: In STEP 1, mean body weight change of −14.9% over 68 weeks versus −2.4% on placebo. In SELECT, a primary cardiovascular endpoint event in 6.5% versus 8.0% on placebo across 17,604 patients. Both are results in named randomised trials of the authorised pharmaceutical product.
What happens when semaglutide is stopped?: The STEP 1 trial extension followed participants for a year after withdrawal and reported that roughly two-thirds of the lost weight returned, with cardiometabolic variables moving back in step. The trial authors concluded that continued treatment appears necessary to maintain the changes.
What are the reported adverse effects?: In SELECT, adverse events leading to permanent discontinuation occurred in 16.6% of the semaglutide group against 8.2% on placebo. Separately, observational work has reported a higher rate of non-arteritic anterior ischaemic optic neuropathy among patients prescribed the compound; that is observational and has not been tested in a trial designed for the question.
Is research-grade semaglutide the same as the prescription product?: No, and the difference is the point. The authorised product is made and released under a marketing authorisation against a pharmacopoeial specification. A research vial has a certificate of analysis and nothing else, and no published trial has studied material of that kind.

Compounds covered

The reference page for each compound this article discusses.

Semaglutide

Tirzepatide: what the research says
A dual GIP and GLP-1 receptor agonist, and the active ingredient of EU-authorised medicines. What the trials reported, and what no trial has studied.
Retatrutide (LY3437943): what the research says
A triple hormone receptor agonist still in development, with no marketing authorisation anywhere. What the published phase 2 work reported, and what it did not.
How to store research peptides
Lyophilised peptides at -20°C, reconstituted at 2–8°C, ambient in transit. Why the dry cake tolerates shipping, and what actually degrades a vial.

About this article

Everything reported here comes from published research, and each finding names the model the study used — cell culture, rat, or human. Findings in one model do not transfer to another, most of the work described is preclinical, and none of it is a claim that a compound is safe or effective for any purpose. Nothing on this page describes doses, routes of administration, or use in a person.

Approval status varies by compound and by country. A few of the substances described are the active ingredient of medicines authorised in the EU; most have no marketing authorisation anywhere and have never been assessed by a regulator. Neither is supplied as a medicine here. All material supplied by ASSAY is sold for in-vitro laboratory research only, and is not a drug, food, cosmetic or medical device, and not for human or veterinary use.

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