Semaglutide: What the Trials Actually Found — and What Changed in 2026

Semaglutide's nausea rate is 44.2%, not the 73% that circulates online. Its muscle-loss claim is backwards. Its gap to tirzepatide is understated threefold. The trials are public; most of the numbers quoted from them are not.

This is the rare compound on this site with a large, genuine human evidence base — dozens of randomised trials, tens of thousands of participants, hard cardiovascular outcomes — which is exactly why secondhand numbers are least excusable here. Semaglutide sits in the weight loss and metabolic peptides category; for dose-conversion arithmetic there is a semaglutide calculator. What follows goes to the trial publications and the current label, claim by claim.

Why is semaglutide's nausea rate quoted at 73% when STEP 1 reports 44.2%?

Semaglutide 2.4 mg produced nausea in 44.2% of STEP 1 participants against 17.4% on placebo, and the 73% figure appears nowhere in that trial. Events were mostly mild to moderate and concentrated during dose escalation, and fewer than 5% of participants stopped treatment for gastrointestinal reasons — 4.5%. STEP 1 randomised 1,961 people and published its safety table, which makes the inflated figure a sourcing failure rather than a disagreement about interpretation.

The tolerability profile has a shape, and the shape matters more than the headline percentage. Nausea clusters in the escalation window and fades with continued dosing, which is why a 44.2% incidence coexists with a 4.5% discontinuation rate.

The boxed warning is rodent thyroid C-cell tumours — animal data, and it should be described as animal data. Semaglutide is contraindicated in personal or family history of medullary thyroid carcinoma or MEN 2. Gallbladder events are associated with rapid weight loss generally; severe persistent abdominal pain requires pancreatitis to be excluded. For cross-compound context, see our peptide side effects hub.

What is semaglutide, and is it built on an exendin-4 backbone?

Semaglutide is a 31-amino-acid analogue of human GLP-1(7-37) with a molecular weight of 4,113.6 g/mol, CAS 910463-68-2, developed by Novo Nordisk under the codes NN9535 and NNC 0113-0217. It is not built on an exendin-4 backbone: exendin-4 is the Gila monster-derived scaffold of exenatide, a different drug entirely. Two modifications do the work — an Aib substitution at position 8 and a C18 fatty-diacid chain on Lys26 — giving a half-life of roughly seven days.

The Aib8 substitution blocks DPP-4, the enzyme that clears native GLP-1 within minutes. The fatty-acid chain drives albumin binding, stretching the half-life to a week and making once-weekly dosing possible. Those two choices are the entire reason a hormone with a minutes-long natural lifespan became a weekly injection.

The exendin-4 error is worth correcting explicitly because it appears in a great deal of published material and it is not a rounding problem — it attributes semaglutide to the wrong molecular lineage. One further naming point for anyone reading vendor catalogues: "GLP-1SG" is a catalog code for semaglutide, not a separate compound, as covered in GLP-1SG explained.

How much weight does semaglutide take off, and does it hold at two years?

Semaglutide 2.4 mg weekly produced 14.9% mean weight loss against 2.4% on placebo over 68 weeks in STEP 1 (n=1,961), and STEP 5 held 15.2% at 104 weeks in 304 patients. Against liraglutide in STEP 8 (n=338) it reached 15.8% versus 6.4%. The 7.2 mg dose in STEP UP (n=1,407) produced 20.7% at 72 weeks. Every figure here is a human randomised controlled trial result.

The placebo figure is −2.4%, not −2.3%. The difference is trivial in itself and useful as a diagnostic: it is the tell for whether a source went to the paper or copied another summary.

Durability held. STEP 5 followed patients to two years and found the 15.2% loss sustained. That is the question most people actually care about, and it is the trial least often cited.

Which cardiovascular figure belongs to which population?

The 26% cardiovascular risk reduction attributed to semaglutide belongs to type 2 diabetes patients in SUSTAIN-6 (n=3,297), where MACE ran 6.6% versus 8.9% for a hazard ratio of 0.74. In obesity without diabetes, SELECT (n=17,604, roughly 40 months) found MACE of 6.5% versus 8.0% — hazard ratio 0.80, a 20% reduction. SELECT is the larger and more recent trial, it underpins the current FDA cardiovascular indication, and it is the one most articles omit.

Both trials are real and both hazard ratios are correct. The error is transplantation: quoting the diabetes number to a reader who does not have diabetes and is asking about obesity treatment. The populations differ, the baseline risk differs, and the effect size differs by six percentage points of relative reduction.

Does semaglutide cause muscle loss?

Semaglutide reduced absolute lean body mass by 9.7% in the STEP 1 DXA substudy of 140 participants — but fat mass fell 19.3% and regional visceral fat 27.4%, so lean tissue rose 3.0 percentage points as a proportion of total body mass. Body composition improved. Articles rating semaglutide's muscle preservation as poor are quoting the absolute figure and ignoring the ratio, which inverts the finding rather than merely blurring it.

Absolute lean mass falls in any substantial weight reduction by any method. What distinguishes one intervention from another is the ratio, and here fat falls roughly twice as fast as lean tissue.

Two related corrections travel with this claim. A widely circulated "fat mass −19.8 kg" figure is a unit error for the −19.3% result, and it is impossible on its face: it exceeds the trial's total mean weight loss of 15.3 kg. And visceral fat in this substudy was measured by DXA, not MRI-PDFF — MRI-PDFF measures liver fat fraction, which is a different tissue and a different question.

The practical implication is unchanged and worth stating plainly: resistance training and adequate protein intake are the sensible mitigations for lean-mass loss during any rapid weight reduction.

How does semaglutide suppress appetite, and does it permanently slow gastric emptying?

Semaglutide works through hypothalamic and brainstem appetite circuits rather than a permanently slower stomach. Friedrichsen et al. (Diabetes, Obesity and Metabolism, 2021) measured ad libitum energy intake 35% lower than placebo — 1,736 versus 2,676 kJ — with reduced hunger and increased satiety, and found no delayed gastric emptying at week 20. Slowed emptying is a real acute effect that attenuates with continued dosing, which is also why nausea concentrates early and fades.

That distinction matters for anyone reasoning about the drug rather than just taking it. If the durable mechanism were mechanical, tolerance to the nausea would imply tolerance to the appetite effect. It does not, because the two run on different systems.

For weight loss through the amylin pathway instead, see cagrilintide; for the dual and triple agonists, tirzepatide and retatrutide.

What changed on the semaglutide label, and which brand was discontinued?

Semaglutide's regulatory position moved six times between early 2024 and mid-2026. Wegovy added cardiovascular risk reduction in March 2024, noncirrhotic MASH with moderate-to-advanced fibrosis in August 2025, oral tablets in December 2025 and the 7.2 mg high dose in March 2026. Ozempic added chronic kidney disease in January 2025 and tablets in January 2026. Rybelsus has been discontinued as a brand, with rollout beginning May 2026.

The oral tablets now carry the Ozempic name. Any source still describing "Rybelsus, daily, fasted" as a current product is out of date.

Two trials drove the newest indications, both human randomised trials. ESSENCE (NEJM, 2025) reported steatohepatitis resolution in 62.9% versus 34.3% on placebo, with fibrosis improvement in 36.8% versus 22.4%. SOUL (NEJM, 2025), in 9,650 patients, found oral semaglutide reduced MACE with a hazard ratio of 0.86.

On sport: semaglutide is not on the WADA Prohibited List. It has been on the Monitoring Program since 2024, and from 1 January 2026 markers of semaglutide and tirzepatide are monitored both in and out of competition. Monitoring is not prohibition, but use is being tracked.

Can you still get compounded semaglutide?

Largely no. FDA declared the semaglutide injection shortage resolved on 21 February 2025, and enforcement discretion for compounders ended 22 April 2025 for 503A pharmacies and 22 May 2025 for 503B outsourcing facilities. FDA has since proposed permanently excluding semaglutide from the 503B bulks list, which if finalised would bar outsourcing facilities from compounding it from bulk substances regardless of any future shortage. What survives is narrow and patient-specific.

That surviving route is 503A compounding under documented clinical-difference exceptions — a verified excipient allergy, or a strength not commercially available. Compounded semaglutide marketed broadly to consumers is operating outside that framework, and this is the change most online guidance has not caught up with.

See can you get semaglutide without a prescription and our FDA peptide regulation timeline.

Which semaglutide claims survive the evidence?

Three of the nine claims most commonly made about semaglutide hold up against the trials, and six do not. The 14.9% weight loss, the two-year durability and the cardiovascular benefit are all supported by named studies with published numbers. The 73% nausea rate, the muscle-loss framing, the roughly two-point tirzepatide gap, the sport ban, the exendin-4 lineage and the legality of compounded supply are variously wrong, backwards, understated threefold or out of date.

What is the approved semaglutide dosing schedule?

Semaglutide's approved schedule starts at 0.25 mg weekly and escalates over months to a standard weight-management dose of 2.4 mg weekly; 7.2 mg was approved in March 2026 and produced −20.7% at 72 weeks in STEP UP. This is prescription medicine and dosing belongs to your prescriber. Semaglutide is approved for chronic use — weight regain after discontinuation is well documented, which makes this maintenance therapy rather than a course.

A "68-week protocol" is a trial duration, not a treatment plan. STEP 1 stopped at 68 weeks because that was its design, not because the drug had finished doing something.

For dose-conversion arithmetic, use the semaglutide calculator alongside the reconstitution calculator, and see the semaglutide dosing chart. For sub-therapeutic dosing practices and what the evidence supports, see GLP-1 microdosing.

How do you verify semaglutide you did not get from a pharmacy?

Semaglutide's characteristic failure mode outside a pharmacy is underdosing, not misidentification. A vial can be 99% pure and still contain substantially less peptide than the label claims, because purity and quantity are separate measurements answering separate questions. Mass spectrometry confirms identity at a mass near 4,113.6 Da; net peptide content or amino acid analysis confirms quantity. A purity figure presented as if it were a quantity is the single most common red flag on this compound.

Start from what grey-market material actually is: unapproved product of unverified identity, purity, quantity and sterility, outside any cold chain, for a drug whose approved version exists on prescription. The mechanism of harm here is rarely a wrong molecule. It is a right molecule in the wrong amount — see why 10 mg isn't 10 mg.

Peptigrity's platform currently tracks 530 shops and 11,852 independent lab tests across 118 peptides, with 1,283 community reviews (verified August 2026). Trust scores weight community reviews and independently verified HPLC purity equally, at 50% each, with no financial relationships influencing the ranking. Independent results are searchable in the lab test database and aggregated in the Purity Index. Live per-milligram pricing across vendors is compared on the semaglutide price page. Those figures exclude shipping, taxes and customs, coupon codes, bulk tiers, multi-vial kits and account-gated pricing.

Vendor-level detail sits on the semaglutide compound page, and the compound-specific walkthrough is in where to buy semaglutide.

How does semaglutide compare with tirzepatide, liraglutide and retatrutide?

Tirzepatide outperformed semaglutide by 6.5 percentage points in SURMOUNT-5 (NEJM, 2025, n=751) — 20.2% versus 13.7% at 72 weeks, the only direct comparison of the two leading agents. Cross-trial estimates had put the gap near two points, so the head-to-head roughly triples it. Against liraglutide, semaglutide won STEP 8 by 15.8% to 6.4%. Retatrutide is not comparable to either yet: its phase 2 work is published and phase 3 is ongoing.

The head-to-head number is the one to carry. Cross-trial comparison across different populations, durations and placebo responses is an estimate; a randomised 751-patient comparison is an answer. See comparing semaglutide and tirzepatide and oral GLP-1 orforglipron vs injectable peptides.

The trial that would settle this

Most of the questions people ask about semaglutide already have randomised answers, which is unusual for this site. STEP 1 (n=1,961) established 14.9% at 68 weeks, STEP 5 held 15.2% to 104 weeks, and SELECT (n=17,604) established cardiovascular benefit at hazard ratio 0.80. Two questions remain genuinely open: how the newly approved 7.2 mg dose performs against tirzepatide, and whether the body-composition result changes when resistance training is built into the protocol.

Frequently Asked Questions

How much weight can you lose on semaglutide?

STEP 1 found 14.9% mean loss at 68 weeks on 2.4 mg, sustained at 15.2% at two years in STEP 5. The 7.2 mg dose produced 20.7% at 72 weeks. Individual results vary widely around those means.

Does semaglutide cause muscle loss?

Absolute lean mass falls about 9.7%, but fat mass falls 19.3% — so lean tissue rises as a proportion of body weight by about 3 percentage points. Resistance training and adequate protein are the standard mitigations.

How bad is the nausea, really?

44.2% of STEP 1 participants reported nausea, mostly mild to moderate and concentrated during escalation. 4.5% discontinued for gastrointestinal reasons. The 73% figure circulating online is not from the trial.

Is semaglutide banned in sport?

No. It is on WADA's Monitoring Program, not the Prohibited List. From January 2026 it is monitored in and out of competition alongside tirzepatide.

Can you still get compounded semaglutide?

Largely no. The shortage was declared resolved in February 2025 and enforcement discretion ended that spring. Only narrow patient-specific exceptions remain, and FDA has proposed permanently excluding semaglutide from the 503B bulks list.

Is Wegovy different from Ozempic?

Same active ingredient, different brands and indications — Wegovy for weight management, cardiovascular risk and MASH; Ozempic for type 2 diabetes, cardiovascular risk and chronic kidney disease. Rybelsus was discontinued as a brand in 2026 and its oral tablets moved under Ozempic.

Where this sits

Semaglutide is the best-evidenced compound covered on this platform: 17,604 patients in a cardiovascular outcomes trial, 104 weeks of durability data in STEP 5, and a randomised head-to-head against liraglutide. That is precisely why the sloppy numbers matter. Quoting a 73% nausea rate that appears in no trial, or a muscle-loss claim the DXA substudy inverts, is choosing secondhand copy over a published paper anyone can read.

The genuinely current issues are different from the ones usually discussed. The head-to-head gap with tirzepatide is larger than most comparisons state, at 6.5 percentage points rather than two. The durability data at two years is stronger than most summaries convey. And the compounding pathway that shaped how a great many people accessed this drug has been closed for over a year.

Browse the weight loss and metabolic peptides category, or our complete peptide guide with 118 compounds (verified August 2026). For per-injection volume, use the semaglutide calculator alongside the reconstitution calculator. Compare shops through independent lab tests and community-verified shop reviews.

This article is for educational and informational purposes only and does not constitute medical advice. Peptides discussed may be investigational compounds not approved by the FDA (or equivalent regulators in your jurisdiction) for human use. Always consult a qualified healthcare provider before using any peptide or research compound. Peptigrity is an independent review platform and does not sell, endorse, or recommend specific products or vendors.