For three years the obesity field argued about tirzepatide versus semaglutide using cross-trial comparison. Then SURMOUNT-5 ran the actual experiment: 751 adults, 72 weeks, both drugs at maximum tolerated doses. Tirzepatide won by 6.5 percentage points.
Tirzepatide is the best-evidenced compound in the weight loss and metabolic peptides category, and its label has moved twice since that trial in ways most content has not caught up with. For per-injection volume on a 2.5 mg titration ladder there is a tirzepatide calculator. What follows is the trial record, the approval record, and what 930 independent lab tests say about the vials.
How much better is tirzepatide than semaglutide?
Tirzepatide produced 20.2% weight loss against semaglutide's 13.7% in SURMOUNT-5, a difference of 6.5 percentage points (P<0.001). The trial randomised 751 adults 1:1 to maximum tolerated doses of each drug for 72 weeks and was published in the New England Journal of Medicine in July 2025. Waist circumference fell 18.4 cm versus 13.0 cm, and tirzepatide was superior at every threshold tested.
Outcome | Tirzepatide | Semaglutide | Difference |
|---|---|---|---|
Weight change | −20.2% (CI −21.4 to −19.1) | −13.7% (CI −14.9 to −12.6) | 6.5 points, P<0.001 |
Waist circumference | −18.4 cm | −13.0 cm | — |
≥10%, ≥15%, ≥20%, ≥25% | Superior at every threshold | — | — |
The trial is Aronne et al., NEJM, July 2025 (PMID 40353578), NCT05822830, comparing tirzepatide at maximum tolerated 10 or 15 mg against semaglutide at maximum tolerated 1.7 or 2.4 mg.
What it replaced was three years of arithmetic across studies that were never designed to be compared: SURMOUNT-1's 20.9% against STEP-1's 14.9%, in different populations, over different durations, with different placebo responses. That is not evidence, and everyone involved knew it. The cross-trial estimate turned out to be roughly right, which does not always happen — and the direct comparison is the one to cite. See our tirzepatide versus semaglutide comparison for the head-to-head in detail.
What is tirzepatide, and why does the fatty diacid matter?
Tirzepatide is a 39-residue synthetic peptide acting as a dual GIP and GLP-1 receptor agonist, CAS 2023788-19-2, molecular weight 4,813.0 g/mol, development code LY3298176. A C20 fatty diacid moiety binds albumin and slows clearance, which is what makes once-weekly dosing possible. That acylation also makes tirzepatide a peptide-lipid conjugate rather than a simple synthetic peptide, and the conjugation chemistry is a manufacturing step grey-market synthesis can get wrong.
Property | Value |
|---|---|
Mechanism | Dual GIP and GLP-1 receptor agonist |
CAS | 2023788-19-2 (PubChem CID 156588324) |
Formula / MW | C₂₂₅H₃₄₈N₄₈O₆₈ / 4,813.0 g/mol |
Structure | 39-residue synthetic peptide with a C20 fatty diacid moiety |
Development code | LY3298176 |
The dual mechanism is the substantive difference from semaglutide. Adding GIP receptor agonism to GLP-1 agonism appears to produce more weight loss than GLP-1 alone, and SURMOUNT-5 is the direct human evidence for that rather than a mechanistic inference.
The manufacturing point deserves emphasis because it changes what a certificate of analysis needs to show. Incomplete acylation produces material that can look clean on HPLC and still be the wrong molecule by mass.
What did SURMOUNT-1 show at each dose?
Tirzepatide produced −15.0% at 5 mg, −19.5% at 10 mg and −20.9% at 15 mg against −3.1% on placebo over 72 weeks in SURMOUNT-1, a 2,539-participant randomised trial published in the New England Journal of Medicine in July 2022. All comparisons reached P<0.001. At least 20% weight loss was achieved by 50% of the 10 mg arm and 57% of the 15 mg arm versus 3% on placebo — the result behind the "about 21%" figure in general circulation.
Dose | Weight change | 95% CI |
|---|---|---|
5 mg | −15.0% | −15.9 to −14.2 |
10 mg | −19.5% | −20.4 to −18.5 |
15 mg | −20.9% | −21.8 to −19.9 |
Placebo | −3.1% | −4.3 to −1.9 |
The trial is Jastreboff et al., NEJM, July 2022 (PMID 35658024), NCT04184622.
Discontinuation due to adverse events ran 4.3%, 7.1% and 6.2% across the three doses against 2.6% on placebo — notably low for this class, and the number worth carrying into any tolerability discussion. For the adverse-event detail, see tirzepatide side effects and the SURMOUNT data.
In type 2 diabetes, Frías et al. (NEJM, 2021, PMID 34170647) ran SURPASS-2 in 1,879 patients over 40 weeks against semaglutide 1 mg: HbA1c fell 2.01 to 2.30 percentage points versus 1.86, with weight differences of −1.9, −3.6 and −5.5 kg, all P<0.001.
What is tirzepatide approved for, and what is it not approved for?
Tirzepatide is approved as Mounjaro (NDA 215866, 13 May 2022) for glycaemic control in type 2 diabetes and as Zepbound (NDA 217806, 8 November 2023) for chronic weight management, both carrying a boxed warning for thyroid C-cell tumours. Zepbound added moderate to severe obstructive sleep apnoea in adults with obesity on 20 December 2024. There is no heart failure, HFpEF or cardiovascular outcome indication on either product.
Mounjaro | Zepbound | |
|---|---|---|
NDA | 215866 | 217806 |
Original approval | 13 May 2022 | 8 November 2023 |
Indication | Glycaemic control in type 2 diabetes | Chronic weight management |
Boxed warning | Thyroid C-cell tumours / MTC / MEN2 | Same |
Change one — obstructive sleep apnoea. The indication arrived via supplement SUPPL-13, approved 20 December 2024. The current label reads: "to treat moderate to severe obstructive sleep apnea (OSA) in adults with obesity." It came from SURMOUNT-OSA (Malhotra et al., NEJM, October 2024, PMID 38912654), two 52-week trials. Apnoea-hypopnoea index fell by 25.3 events per hour versus 5.3 on placebo in participants not using PAP (difference −20.0, P<0.001), and by 29.3 versus 5.5 in those on PAP (difference −23.8, P<0.001).
Change two — paediatric type 2 diabetes. Mounjaro's current label covers "adults and pediatric patients 10 years of age and older with type 2 diabetes mellitus," following supplement SUPPL-39 approved 19 December 2025. Anything describing Mounjaro as adults-only is out of date.
What is not approved, despite persistent claims: Zepbound's approval history contains exactly one efficacy-new-indication supplement since launch — the OSA one. SUMMIT data exist; an indication does not. The boxed warning rests on rodent thyroid C-cell tumour findings, and should be described as animal data rather than a human observation.
Which tirzepatide claims survive the evidence?
Four of the ten claims most commonly made about tirzepatide are false or out of date: that it is approved for heart failure, that its label is adults-only, that it carries no serious warnings, and that it is banned in sport. Tirzepatide does not appear anywhere on the WADA 2026 Prohibited List, and it does carry a boxed warning. The FDA approvals, the head-to-head superiority over semaglutide, the sleep apnoea indication and the roughly 21% average loss all hold.
Claim | Evidence | Verdict |
|---|---|---|
FDA-approved | Mounjaro NDA 215866 (2022), Zepbound NDA 217806 (2023) | True |
Beats semaglutide for weight loss | SURMOUNT-5 head-to-head: 6.5 points, P<0.001 | Established |
Approved for sleep apnoea | Yes — Zepbound SUPPL-13, 20 Dec 2024 | True |
Approved for heart failure | No such indication exists | False |
Adults only | Mounjaro covers ages 10+ since Dec 2025 | Outdated |
~21% average weight loss | SURMOUNT-1 15 mg: −20.9% over 72 weeks | True |
Well tolerated | Discontinuation 4.3–7.1% vs 2.6% placebo | Comparatively, yes |
No serious warnings | Boxed warning: thyroid C-cell tumours | False |
On FDA's compounding risk list | Not on either FDA table | Not listed |
Banned in sport | Not on the WADA 2026 Prohibited List | False |
As an approved drug, tirzepatide is also not captured by WADA's S0 catch-all, which applies to substances with no regulatory approval for human therapeutic use.
Can compounding pharmacies still sell tirzepatide?
Not as a copy of the approved product. Compounding an essential copy was permitted only while tirzepatide was in shortage, and FDA's shortage database now lists Tirzepatide Injection as "Resolved" — semaglutide injection likewise. Tirzepatide appears on neither of FDA's bulk substances tables, but that absence is not permission; the operative mechanism was always the shortage list, and it has closed. The peer-reviewed summary is blunt about the consequence.
Sections 503A and 503B of the Food, Drug and Cosmetic Act allow compounding of a drug that is essentially a copy of an approved product only while that product is in shortage. We enumerated both tables on the page current 22 April 2026: no GLP-1, GIP, glucagon or amylin agonist appears on either.
Belcourt, Sapowadia & White, writing in Annals of Pharmacotherapy in September 2026, state it directly: "With the shortage of innovator semaglutide or tirzepatide products resolved, compounding pharmacies can only legally sell unique products."
We could not verify the specific resolution dates or the wind-down deadlines from a primary FDA page, so we are not printing them. The current status is verifiable and it is what matters.
FDA's other warnings on this class are specific and worth quoting. From its page on unapproved GLP-1 drugs used for weight loss:
On salt forms: "These salt forms... are different active ingredients than are used in the approved drugs. The agency does not have information on whether these salts have the same chemical and pharmacologic properties." This is the semaglutide sodium and semaglutide acetate issue, and the same logic applies to any tirzepatide salt.
On research-use labelling: "FDA has warned companies that have illegally sold unapproved drugs... falsely labeled 'for research purposes' or 'not for human consumption.' These products have been sold directly to consumers for human use."
On dosing errors: FDA received "multiple reports of adverse events... that may be related to dosing errors associated with compounded injectable semaglutide products," resulting from patients measuring and self-administering incorrect doses.
As of 30 November 2024, FDA had received more than 215 adverse event reports for compounded tirzepatide and more than 392 for compounded semaglutide. Those are spontaneous reports rather than trial data, and the figures have not been updated since. See our FDA peptide regulation timeline and compounding pharmacy versus research peptide.
What do 930 independent lab tests show about tirzepatide vials?
The Purity Index records tirzepatide at 99.75% average across 930 independent tests (verified August 2026) — one of the deepest datasets on this platform — from Freedom Diagnostics, Kovera, ILS, Accumark and MZ Biolabs, across 227 shops selling. Identity is not the failure mode here. Quantity is: variance runs +2.6% to +26.7%, with vials labelled 10 to 65 mg testing between 10.71 and 68.1 mg.
A 26.7% overage on a drug titrated in 2.5 mg steps is a clinically meaningful dosing error, and it runs in the direction that causes the gastrointestinal adverse effects people discontinue for. That is the practical risk for this compound: not that the material is something else, but that there is more of it in the vial than the label says. See why 10 mg isn't 10 mg and tirzepatide dosing and reconstitution.
Check | What it confirms | How | Red flag |
|---|---|---|---|
Mass spectrometry | 4,813.0 Da with the C20 diacid attached | Batch-matched CoA with MS | HPLC purity alone — incomplete acylation changes the mass |
Salt form | Free base versus a salt FDA says is a different active ingredient | Stated form on the CoA | Not stated |
Fill accuracy | Vial matches label | Quantitative content testing | +26.7% is on record — the main risk here |
Net peptide content | Peptide versus salts and water | Net content or amino acid analysis | Purity quoted as quantity |
Endotoxin (LAL) | No pyrogens | LAL result on the batch | Field blank |
Tirzepatide price data shows 14 shops in stock, median $5.67/mg, lowest $1.17/mg on a 60 mg vial (verified 9 August 2026), across 48 compared offers with vial prices from $19.99 to $465.00. By vial size: 5–10 mg runs a median $9.60/mg, 15–35 mg $5.69/mg, and 40–120 mg $3.85/mg. Those figures exclude shipping, taxes and customs, coupon codes, bulk tiers, multi-vial kits and account-gated pricing. To turn a per-milligram price into a per-dose cost, use the cost-per-dose calculator.
Peptigrity's platform currently tracks 530 shops and 11,852 independent lab tests across 118 peptides, with 1,283 community reviews (verified August 2026), and trust scores weight community reviews and independently verified HPLC purity equally at 50% each. Compare vendors on the tirzepatide compound page, search results in the lab test database, and see where to buy tirzepatide.
How does tirzepatide compare with the other incretin agonists?
Tirzepatide's −20.9% in SURMOUNT-1 (n=2,539, 72 weeks) sits above semaglutide's −14.9% in STEP-1, CagriSema's −20.4% in REDEFINE-1, mazdutide's −16.65% in GLORY-2 and survodutide's −13.0% in SYNCHRONIZE-1, and below retatrutide's −24.2% — which is a phase 2 figure from 338 participants over 48 weeks rather than a phase 3 result. Only the semaglutide comparison has been run head-to-head. Cross-trial comparison is not: populations, durations and placebo responses differ, and survodutide's placebo arm alone lost 5.4%.
Compound / dose | Trial | n | Duration | Weight change | Placebo |
|---|---|---|---|---|---|
Semaglutide 2.4 mg | STEP-1 | 1,961 | 68 wk | −14.9% | −2.4% |
Tirzepatide 15 mg | SURMOUNT-1 | 2,539 | 72 wk | −20.9% | −3.1% |
Retatrutide 12 mg | Phase 2 | 338 | 48 wk | −24.2% | −2.1% |
REDEFINE-1 | 3,417 | 68 wk | −20.4% | −3.0% | |
Mazdutide 9 mg | GLORY-2 | 461 | 60 wk | −16.65% | −1.50% |
Survodutide 6 mg | SYNCHRONIZE-1 | 725 | 76 wk | −13.0% | −5.4% |
Two things stand out. CagriSema — two drugs — landed at 20.4%, essentially where tirzepatide alone landed. And survodutide's placebo arm lost 5.4%, nearly double most trials, which compresses its placebo-adjusted effect and makes naive comparison misleading.
Also worth noting for anyone building a current picture: orforglipron (Foundayo), an oral GLP-1, was FDA-approved on 1 April 2026 for obesity. See oral GLP-1: orforglipron versus peptides.
The trial that would settle this
Tirzepatide is the rare compound on this site where the important trials have been run rather than merely proposed. SURMOUNT-5 answered the semaglutide comparison at 6.5 percentage points in 751 patients, SURMOUNT-1 answered obesity efficacy in 2,539, and SURMOUNT-OSA answered sleep apnoea and produced an approved indication. Three questions remain genuinely open: the head-to-head against retatrutide, a cardiovascular indication, and durability past 72 weeks.
Question | Status |
|---|---|
Does it beat semaglutide? | Answered — SURMOUNT-5, 6.5 points, P<0.001 |
Does it work for obesity? | Answered — SURMOUNT-1, n=2,539 |
Does it treat sleep apnoea? | Answered — SURMOUNT-OSA, approved indication |
Does it beat retatrutide? | Trial registered and ongoing (NCT06662383) |
Cardiovascular outcomes | Data exist; no approved indication |
Long-term durability beyond 72 weeks | Open |
Frequently Asked Questions
Does tirzepatide beat semaglutide?
Yes, in a direct head-to-head trial. SURMOUNT-5 randomised 751 adults to maximum tolerated doses of each for 72 weeks: tirzepatide −20.2% versus semaglutide −13.7%, a difference of 6.5 percentage points, P<0.001, with superiority at every weight-loss threshold tested.
Is tirzepatide approved for sleep apnoea?
Yes. Zepbound gained the indication on 20 December 2024 for moderate to severe obstructive sleep apnoea in adults with obesity, based on SURMOUNT-OSA, which showed apnoea-hypopnoea index reductions of 25.3 and 29.3 events per hour versus around 5 on placebo.
Is it approved for heart failure?
No. Neither Mounjaro nor Zepbound carries a heart failure, HFpEF or cardiovascular outcome indication. The only new efficacy indication added since launch is obstructive sleep apnoea.
Can compounding pharmacies still sell tirzepatide?
Not as a copy of the approved product. Compounding an essential copy was permitted only while tirzepatide was in shortage, and FDA's shortage database now lists Tirzepatide Injection as resolved. As the peer-reviewed summary puts it, compounders "can only legally sell unique products."
What about tirzepatide salt forms?
FDA has stated that salt forms of these peptides "are different active ingredients than are used in the approved drugs" and that the agency lacks information on whether they have the same chemical and pharmacologic properties. A certificate of analysis should state the form.
What is the main quality risk with research-market tirzepatide?
Fill quantity. Our platform's 930 tests show identity is broadly reliable, but quantity variance runs +2.6% to +26.7% against label. On a drug titrated in 2.5 mg increments, a 27% overage is a real dosing error in the direction that causes nausea and vomiting.
Where this sits
Tirzepatide is the best-evidenced compound covered on this platform, and everything difficult about it now sits on the supply side rather than the evidence side. SURMOUNT-5 settled the semaglutide argument in 751 randomised patients over 72 weeks. Discontinuation for adverse events ran 4.3% to 7.1% against 2.6% on placebo. Meanwhile FDA has logged more than 215 adverse event reports for compounded tirzepatide, and our own testing finds fill variance reaching +26.7%.
The shortage that legitimised compounding has resolved. FDA has said in writing that salt forms are different active ingredients, and that "research purposes" labelling does not exempt a seller. On this platform, one in a handful of tested vials contains a quarter more drug than the label claims.
The molecule works, and the trials that establish it are large, recent and directly comparative. The open question for anyone buying outside a pharmacy is narrower and more practical: whether the vial in front of them contains what those trials tested, at the dose they think it does.
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 tirzepatide calculator and the cost-per-dose 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.
