Peptide Evidence Index

Semaglutide

Evidence last reviewed: September 2026

Quick answers

What is it?: Semaglutide is a synthetic version of the human hormone GLP-1, engineered to last about a week in the body, sold as Ozempic and Rybelsus for diabetes and Wegovy for weight management.
Why are people interested in it?: It is one of the most extensively studied drugs of the last decade, with trials showing weight loss, blood-sugar control, and reduced cardiovascular events.
What has actually been studied?: Large, multi-year, company-run randomized trials in adults with obesity, type 2 diabetes, and existing cardiovascular disease, some enrolling over 17,000 people.
How strong is the evidence?: Very strong for its approved uses, but nearly all of it comes from trials designed and funded by the manufacturer in specific, carefully defined populations.
What don't we know yet?: Multi-decade safety, and whether its cardiovascular benefit extends to people younger than 45 or without existing heart disease.
Where can I read the original research?: Sources at the bottom of this page: STEP 1 (Wilding et al., NEJM 2021) and SELECT (Lincoff et al., NEJM 2023).

Plain-English overview

Semaglutide is a synthetic version of the human hormone GLP-1 (glucagon-like peptide-1), altered with amino-acid substitutions and a fatty-acid side chain that lets it bind albumin in the blood, extending its half-life from the native hormone's few minutes to about one week. It is FDA-approved as Ozempic and the oral tablet Rybelsus for type 2 diabetes, as Wegovy for chronic weight management, and, since 2024, for reducing cardiovascular risk in people who already have cardiovascular disease and overweight or obesity. It is one of the most extensively studied drugs of the last decade: 746 studies listing it as an intervention are registered on ClinicalTrials.gov, and several of its pivotal trials — including one of more than 17,000 participants — rank among the largest ever run for a chronic, non-infectious condition. Across that program it has consistently lowered blood sugar, produced substantial weight loss, and reduced cardiovascular events. Nearly all of this evidence comes from company-run, multi-year trials in specific, carefully defined populations, and weight regain after stopping is well documented.

What researchers are studying it for

Type 2 diabetes (glycemic control)
Chronic weight management in overweight/obesity
Cardiovascular risk reduction in adults with overweight/obesity and known cardiovascular disease

Current evidence level

Randomized trials

Regulatory status: Approved medicine. Evidence strength and approval are scored separately; approval is a regulatory decision about a specific use, not a measure of how much research exists.

Human research

STEP 1 (Wilding et al., NEJM 2021) randomized 1,961 adults with obesity, or overweight plus a weight-related condition and no diabetes, to weekly semaglutide 2.4 mg or placebo for 68 weeks alongside lifestyle counseling; the semaglutide group lost a mean 14.9% of body weight versus 2.4% with placebo. This is the trial behind the Wegovy approval. SELECT (Lincoff et al., NEJM 2023) randomized 17,604 adults age 45 and older with pre-existing cardiovascular disease and a BMI of 27 or higher, but no diabetes, to weekly semaglutide 2.4 mg or placebo; over a mean 39.8 months, semaglutide cut the combined rate of cardiovascular death, non-fatal heart attack, or non-fatal stroke from 8.0% to 6.5% of participants, a 20% relative reduction. This is the trial behind the 2024 cardiovascular-risk indication. SUSTAIN-6 (Marso et al., NEJM 2016) tested semaglutide's cardiovascular safety in adults with type 2 diabetes at high cardiovascular risk, randomizing participants to weekly semaglutide or placebo added to standard care, and found a reduction in cardiovascular events — establishing semaglutide's cardiovascular signal in diabetes ahead of SELECT's later finding in people without diabetes. STEP 2 (Davies et al., Lancet 2021) tested semaglutide 2.4 mg specifically in adults with type 2 diabetes and overweight or obesity, a population that generally loses less weight on incretin drugs, over 68 weeks, and found significantly greater weight loss and HbA1c reduction than placebo. In the STEP 1 extension (Wilding et al., 2022), 327 participants who had lost a mean 17.3% of body weight on semaglutide regained about two-thirds of that loss — 11.6 of the 17.3 percentage points — within a year of stopping the drug and the lifestyle program together.

Animal and preclinical research

As with other drugs in this class, rodent studies found thyroid C-cell tumors with semaglutide, the basis for its boxed warning and its contraindication in people with a personal or family history of medullary thyroid carcinoma or multiple endocrine neoplasia type 2. Whether this rodent finding applies to humans has not been confirmed or ruled out. The source material reviewed here does not describe other animal studies in detail.

Major findings

STEP 1: mean 14.9% body-weight loss over 68 weeks versus 2.4% with placebo, in 1,961 adults with obesity/overweight without diabetes.
SELECT: 20% relative reduction in cardiovascular death, heart attack, or stroke over a mean 39.8 months in 17,604 adults with existing cardiovascular disease.
SUSTAIN-6: reduced cardiovascular events in adults with type 2 diabetes at high cardiovascular risk.
STEP 2: significant weight loss and glycemic improvement in adults with both type 2 diabetes and overweight/obesity.
STEP 1 extension: about two-thirds of lost weight was regained within a year of stopping semaglutide and lifestyle support.
746 studies registered on ClinicalTrials.gov, with hundreds posting results.

What has not been established

Multi-decade safety — the longest pivotal trial (SELECT) ran a mean of about 40 months.
Whether the rodent thyroid C-cell tumor signal applies to humans.
Cardiovascular benefit in people younger than 45 or without existing cardiovascular disease — SELECT enrolled an older population with disease already present.
Safety in pregnancy, which was excluded from both STEP 1 and SELECT.
Use alongside other weight-loss drugs, which the pivotal trials did not test.

Important limitations

Nearly all pivotal evidence is company-run, multi-year, and industry-funded.
STEP 1 and SELECT both excluded people with a personal or family history of medullary thyroid carcinoma/MEN2 and a history of pancreatitis; STEP 1 also excluded diabetic-range HbA1c.
SELECT's population — people 45 and older with existing cardiovascular disease — does not automatically represent younger or disease-free users.
Most of the 746 registered trials are pharmacokinetic, dose-finding, or comparator studies, not independent replications of the pivotal endpoints.
Weight regain after stopping is well documented, meaning trial results reflect an ongoing-treatment effect, not a one-time change.

Regulatory status

Approved by the FDA as Ozempic (subcutaneous injection) in December 2017 for type 2 diabetes; as Rybelsus (oral tablet) in September 2019, also for type 2 diabetes; as Wegovy (subcutaneous injection, 2.4 mg maintenance dose) in June 2021 for chronic weight management; and with an added indication in March 2024 for reducing cardiovascular death, heart attack, and stroke in adults with cardiovascular disease and obesity or overweight. Not on the World Anti-Doping Agency's Prohibited List.

Primary research sources

Wilding JPH et al., STEP 1: Once-Weekly Semaglutide in Adults with Overweight or Obesity: NEJM 2021; PMID 33567185; ClinicalTrials.gov NCT03548935
Lincoff AM et al., SELECT: Semaglutide and Cardiovascular Outcomes in Obesity without Diabetes: NEJM 2023; PMID 37952131; ClinicalTrials.gov NCT03574597
Wilding JPH et al., STEP 1 extension (post-treatment follow-up): 2022; PMID 35441470
Marso SP et al., SUSTAIN-6: Semaglutide and Cardiovascular Outcomes in Type 2 Diabetes: NEJM 2016; PMID 27633186; ClinicalTrials.gov NCT01720446
Davies M et al., STEP 2: Semaglutide in Type 2 Diabetes and Overweight/Obesity: Lancet 2021; PMID 33667417; ClinicalTrials.gov NCT03552757

Full evidence entry (complete data, registry records, dosing evidence)

Approved medicine

Approved by a major regulator for a specific use

At a glance

Also known as: Ozempic, Wegovy, Rybelsus
Class: GLP-1 receptor agonist
Derived from: A synthetic analog of human glucagon-like peptide-1 (GLP-1), altered with amino-acid substitutions and a fatty-acid side chain that binds albumin in the blood, extending its half-life from the native hormone's few minutes to about one week
Registered human trials: 746
…with published results: hundreds — including every pivotal trial cited below (counted on ClinicalTrials.gov this session; most of the registered total are dose-finding, pharmacokinetic, or comparator studies rather than independent replications of the pivotal endpoints)
Largest human trial: 17,604 adults with established cardiovascular disease and overweight or obesity but no diabetes (SELECT, 2023) — semaglutide reduced the composite of cardiovascular death, non-fatal heart attack, or non-fatal stroke by 20% versus placebo over a mean of 39.8 months
Studied for: type 2 diabetes (glycemic control), chronic weight management in overweight/obesity, cardiovascular risk reduction in adults with overweight/obesity and known cardiovascular disease
Dosing evidence: Prescribed by a clinicianEvery studied dose was reached through a supervised weekly step-up schedule set by the trial protocol and, in practice, by a prescriber following the FDA-approved label — not a fixed starting amount a person selects on their own.
Regulatory status: Approved by the FDA as Ozempic (subcutaneous injection) in December 2017 for type 2 diabetes; as Rybelsus (oral tablet) in September 2019, also for type 2 diabetes; as Wegovy (subcutaneous injection, 2.4 mg maintenance dose) in June 2021 for chronic weight management in adults, and later adolescents, with obesity or overweight plus a weight-related condition; and with an added indication in March 2024 for reducing the risk of cardiovascular death, heart attack, and stroke in adults with cardiovascular disease and obesity or overweight.
Anti-doping status: Not on the World Anti-Doping Agency's Prohibited List

What it is

Semaglutide is a synthetic version of human GLP-1 (glucagon-like peptide-1), a hormone the gut releases after eating that tells the pancreas to release insulin and tells the brain to reduce appetite. The native hormone is broken down by the body within minutes. Semaglutide's molecule is altered — a few amino acids are swapped and a fatty-acid chain is attached — so it resists that breakdown and binds to albumin in the blood, giving it a half-life of about one week. That is what allows once-weekly injections, or a daily oral tablet in a specially formulated version.

It is an FDA-approved medicine: as Ozempic and Rybelsus for type 2 diabetes, as Wegovy for chronic weight management, and, since 2024, for reducing cardiovascular risk in people who already have cardiovascular disease and overweight or obesity.

What the studies actually found

Semaglutide's approvals rest on a large program of company-run randomized trials, several of them among the largest drug trials ever conducted for a chronic, non-infectious condition.

STEP 1 (Wilding et al., NEJM 2021; PubMed PMID 33567185, DOI) randomly assigned 1,961 adults with obesity, or overweight plus a weight-related condition, none of whom had diabetes, to weekly subcutaneous semaglutide 2.4 mg or placebo for 68 weeks, alongside lifestyle counseling. The semaglutide group lost a mean 14.9% of body weight versus 2.4% with placebo — a gap of roughly 12 percentage points. This is the trial behind the Wegovy approval.

SELECT (Lincoff et al., NEJM 2023; PubMed PMID 37952131, DOI) is larger still: 17,604 adults age 45 and older with pre-existing cardiovascular disease and a BMI of 27 or higher, but no diabetes, randomized to weekly semaglutide 2.4 mg or placebo. Over a mean follow-up of 39.8 months, semaglutide cut the combined rate of cardiovascular death, non-fatal heart attack, or non-fatal stroke from 8.0% to 6.5% of participants — a 20% relative reduction (hazard ratio 0.80). This is the trial behind the 2024 cardiovascular-risk indication.

Earlier trials not detailed here established semaglutide's glucose-lowering effect in type 2 diabetes and its performance against other GLP-1 drugs, including a head-to-head loss to tirzepatide in SURPASS-2 (see the tirzepatide profile).

What exists in humans

As of this session, 746 studies listing semaglutide as an intervention are registered on ClinicalTrials.gov — everything from single-dose pharmacokinetic studies to the 17,604-person SELECT trial. That volume, and the fact that the pivotal trials were large, multi-year, multi-country, and independently published in peer-reviewed journals with posted results, is itself part of the evidence picture: this is not a compound with a thin or ambiguous human record.

It is also a studied population with real boundaries. STEP 1 and SELECT both excluded people with a personal or family history of medullary thyroid carcinoma or multiple endocrine neoplasia type 2, and a history of pancreatitis; STEP 1 additionally excluded anyone with an HbA1c in the diabetic range. SELECT enrolled people 45 and older with existing cardiovascular disease specifically — its cardiovascular-benefit finding does not automatically extend to younger, disease-free people taking the drug only for weight loss. Both trials excluded pregnant participants, and semaglutide's safety in pregnancy has not been established by this evidence.

What doses have been studied in humans

Every trial of semaglutide used a supervised, gradual dose-escalation schedule, not a single fixed amount from day one. In STEP 1, 1,961 adults without diabetes received once-weekly subcutaneous injections, titrated over about 16 weeks up to a 2.4 mg maintenance dose, continued to week 68; the primary endpoint was percent change in body weight. In SELECT, 17,604 adults with cardiovascular disease received the same titrated regimen up to 2.4 mg weekly for a mean exposure of 34.2 months; the primary endpoint was time to a cardiovascular event. Earlier diabetes trials used lower maintenance doses with the same titration logic.

This is a prescription medicine sold under an FDA-approved label, and the label — not a trial protocol summarized on a website — is what specifies how a given patient should start and adjust their dose, based on their indication, response, and side effects, under a prescriber's supervision. Nothing here is a substitute for that label or that supervision, and none of it describes what any individual reader should take.

What remains unknown

What happens after stopping. In the STEP 1 extension (Wilding et al., 2022; PMID 35441470, DOI), 327 participants who had lost a mean 17.3% of body weight on semaglutide regained about two-thirds of that loss — 11.6 of the 17.3 percentage points — within a year of stopping the drug and the lifestyle program together. Cardiometabolic improvements reversed in parallel. The trial authors concluded ongoing treatment is required to maintain the benefit: this is treatment for a chronic condition, not a course with a defined endpoint.
Long-term safety beyond the trial windows. STEP 1 ran 68 weeks; SELECT ran a mean of about 40 months. Multi-decade safety is not established one way or the other.
Thyroid C-cell tumors. Semaglutide carries a boxed warning based on rodent studies showing thyroid C-cell tumors; whether this risk translates to humans has not been confirmed or ruled out, which is why the drug is contraindicated in people with a personal or family history of medullary thyroid carcinoma or MEN2.
Use outside the studied populations. SELECT's cardiovascular finding applies to people 45 and older with existing cardiovascular disease, not necessarily to younger or disease-free people using the drug for weight loss alone. Use in pregnancy and alongside other weight-loss drugs is not established by these trials.

Registry and study records

STEP 1: Once-Weekly Semaglutide in Adults with Overweight or Obesity: ClinicalTrials.gov NCT03548935 · n=1,961, completed 2021, results posted; Wilding et al., NEJM 2021
SELECT: Semaglutide and Cardiovascular Outcomes in Obesity without Diabetes: ClinicalTrials.gov NCT03574597 · n=17,604, completed 2023, results posted; Lincoff et al., NEJM 2023

See the full Evidence Index →

Evidence last reviewed: September 2026. Peptide Proof reports what studies found. We do not give medical advice, dosing guidance, or treatment recommendations.