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Tirzepatide Clinical Trials: What the Data Show

Creator: Elena Marsh, Health Writer
Published: 2026-08-09

Two phase 3 programmes, a cardiovascular outcome trial that reported in December 2025, and more than 18,000 participants — here is what the published evidence actually shows, dose by dose.

Elena Marsh, Health Writer August 9, 2026 15 min read

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The short version

In SURMOUNT-1 (2,539 adults with obesity or overweight, no type 2 diabetes), mean weight change at 72 weeks was −15.0%, −19.5% and −20.9% on 5/10/15 mg versus −3.1% on placebo.
In SURMOUNT-1, 91% of the 15 mg group reached at least 5% weight loss and 57% reached at least 20%; the placebo figures were 35% and 3%.
SURMOUNT-2 (938 adults with obesity and type 2 diabetes) showed −12.8% at 10 mg and −14.7% at 15 mg versus −3.2% placebo at 72 weeks — less than without diabetes.
In SURPASS-2 (1,879 adults with type 2 diabetes on metformin), HbA1c fell 2.01, 2.24 and 2.30 percentage points on 5/10/15 mg at 40 weeks versus 1.86 on semaglutide 1.0 mg.
SURPASS-CVOT (more than 13,000 adults with type 2 diabetes and cardiovascular disease, published December 2025) found major adverse cardiovascular events in 12.2% on tirzepatide versus 13.1% on dulaglutide — noninferior, not an advantage.
Gastrointestinal effects drove most withdrawals: 4.3–7.1% of tirzepatide participants stopped for adverse events versus 2.1–2.6% on placebo, with symptoms concentrated during dose escalation.

The tirzepatide clinical trials that built the evidence base — the SURPASS programme in type 2 diabetes and the SURMOUNT programme in obesity — are specific about who was enrolled, at what dose, and for how long. That matters, because the headline percentage moves a long way depending on which trial produced it and whether the participants had diabetes. This page covers what each trial measured, what the published figures were, how the molecule produces those effects, and where the evidence runs out.

What tirzepatide is

Tirzepatide is a single synthetic peptide, 39 amino acids long, that activates two different incretin receptors — the GIP receptor and the GLP-1 receptor — from one molecule, given as a once-weekly injection under the skin. It is engineered on the native GIP sequence rather than the GLP-1 sequence, which is why it is described as a dual GIP/GLP-1 receptor agonist rather than a GLP-1 drug.

Three chemical modifications explain the weekly schedule. A C20 fatty diacid is attached to a lysine residue, giving reversible, high-affinity binding to albumin in the blood — effectively a circulating reservoir that releases the peptide slowly. Two non-coded amino-isobutyric acid (Aib) substitutions block recognition by DPP-4, the enzyme that destroys native incretins within minutes. Further substitutions add resistance to other proteases and slow renal clearance. The result is a plasma half-life of roughly 5 days, against about 2 minutes for native GLP-1 and about 7 minutes for native GIP. Exposure rises in proportion to dose across the 2.5 mg to 15 mg range, and steady-state concentrations are reached after about 4 weeks of weekly dosing.

Tirzepatide is not an investigational molecule. It cleared phase 3 development and regulatory review, and reaches patients as two branded products — Mounjaro, for type 2 diabetes in adults, and Zepbound, for weight management. The compounded formulation described later on this page is not FDA-approved, and the distinction between the two is covered in full below.

How tirzepatide works on two receptors at once

Tirzepatide works by activating the GLP-1 receptor and the GIP receptor simultaneously, from one molecule, at a fixed ratio. The GLP-1 arm mainly suppresses appetite and slows the stomach; the GIP arm mainly changes how fat tissue handles nutrients and how the brain values food; together they raise insulin output more than either pathway does alone.

The GLP-1 arm. GLP-1 is released by L-cells in the intestine when food arrives. Its receptor sits on pancreatic beta cells, on hypothalamic neurons, and on gastrointestinal smooth muscle. The receptor is Gs-coupled: activation drives adenylyl cyclase, raises intracellular cAMP, and increases protein kinase A activity. In the islet, that potentiates glucose-stimulated insulin secretion while reducing glucagon output from alpha cells. In the brain, GLP-1 receptor engagement in the arcuate and paraventricular nuclei activates POMC neurons and inhibits NPY, cutting food intake in a dose-dependent way. In the gut, the same receptor delays gastric emptying through vagal afferent signalling, stretching out nutrient absorption and prolonging fullness after a meal.

The GIP arm. GIP comes from K-cells in the duodenum and jejunum, and its receptor is found on beta cells, on adipocytes, on bone, and in selected regions of the brain. GIP was written off as a diabetes target for years, because the insulin response to injected GIP is blunted in type 2 diabetes — attributed to receptor downregulation and desensitisation. What changed the picture is that GIP receptor activation enhances insulin secretion when the GLP-1 receptor is being stimulated at the same time. The mechanism behind that cross-talk is still open: proposed explanations include receptor heterodimerisation, shared downstream signalling scaffolds and better receptor trafficking to the cell surface, or epigenetic changes that raise GIP receptor expression. In fat tissue, GIP receptor signalling shifts lipid handling through the PPARγ and C/EBP transcriptional pathways, increases insulin-stimulated glucose uptake, and lowers inflammatory cytokine output; in obese mice, GIP receptor agonism produced insulin sensitisation independent of weight loss. In the brain, it modulates reward-driven eating through mesolimbic dopamine circuits — hedonic intake rather than hunger — and restores leptin sensitivity in hypothalamic neurons.

Why one molecule beats the sum of its parts. GIP receptor activation potentiates GLP-1-receptor-dependent cAMP generation inside islets, amplifying insulin release while preserving glucose-dependency — which is why hypoglycaemia risk stays low even at the top dose. Dual engagement raises cAMP above what either pathway reaches alone, increasing ATP production, calcium influx and insulin granule exocytosis. In primary human islets both receptors are needed for the full effect: blocking the GIP receptor substantially reduces the insulin response to tirzepatide.

Imbalanced and biased. The two activities are not matched. Tirzepatide is roughly equipotent with native GIP at the GIP receptor but binds the GLP-1 receptor about five-fold less tightly than native GLP-1 does. In cAMP assays it behaves as a full agonist at both, with EC50 values indicating preferential GIP receptor activation at lower concentrations and progressive GLP-1 receptor recruitment as the dose rises. At the GLP-1 receptor it also shows biased signalling: it favours the Gs/cAMP route over β-arrestin recruitment, so the receptor is internalised and desensitised less, stays on the cell surface longer, and keeps signalling. In primary human islets, β-arrestin1 limits the insulin response to native GLP-1 but not to GIP or to tirzepatide.

Because GIP receptor agonism has little effect on gastric emptying, the dual design was intended to add weight-loss effect without adding proportionally to the nausea that caps how far a GLP-1-selective drug can be pushed. Preclinical work supports that idea; no clinical trial testing it head-to-head at matched weight loss has been published.

What the tirzepatide clinical trials set out to measure

Two separate phase 3 programmes were run. SURPASS tested glycaemic control in adults with type 2 diabetes, against placebo and against active comparators. SURMOUNT tested weight reduction in adults with obesity, with and without diabetes. All were randomised, and the readouts below are means from the trial populations, not forecasts for any individual.

That distinction is the useful thing to hold on to: a number from SURMOUNT-1 describes adults without type 2 diabetes, and the same dose produced a smaller change in adults who had it. A third trial, SURMOUNT-4, was built specifically to test what happens when treatment is withdrawn, and it is covered below.

SURMOUNT-1 and SURMOUNT-2: the weight results

At 72 weeks, mean body-weight reduction in adults without type 2 diabetes reached 20.9% on the 15 mg dose against 3.1% on placebo. In adults who had type 2 diabetes as well as obesity, the same dose produced 14.7% against 3.2% on placebo.

SURMOUNT-1 enrolled 2,539 adults with a BMI of 30 or above, or 27 or above with a weight-related health condition, and excluded people with type 2 diabetes. SURMOUNT-2 enrolled 938 adults with obesity and type 2 diabetes — a group historically less responsive to weight-loss medication.

Trial	Population	Arm (weekly)	Mean weight change at 72 weeks	Reached ≥5% loss	Reached ≥20% loss
SURMOUNT-1	2,539 adults, obesity/overweight, no type 2 diabetes	5 mg	−15.0%	85%	not reported
SURMOUNT-1	same	10 mg	−19.5%	89%	50%
SURMOUNT-1	same	15 mg	−20.9%	91%	57%
SURMOUNT-1	same	placebo	−3.1%	35%	3%
SURMOUNT-2	938 adults, obesity with type 2 diabetes	10 mg	−12.8%	79%	not reported
SURMOUNT-2	same	15 mg	−14.7%	83%	not reported
SURMOUNT-2	same	placebo	−3.2%	32%	not reported

All comparisons against placebo in SURMOUNT-1 were reported at p<0.001, and the 5% threshold is the conventional marker of clinically meaningful weight change in obesity medicine. Note the responder figures carefully: 91% is the 15 mg result and 89% the 10 mg result — a pairing frequently garbled in secondary write-ups of this trial.

SURMOUNT-4: what happened when treatment was withdrawn

SURMOUNT-4 tested maintenance directly. All 670 participants took tirzepatide open-label for 36 weeks at their maximum tolerated dose — 10 or 15 mg weekly — and averaged 20.9% weight reduction across that lead-in. They were then randomised either to continue or to switch to placebo for a further 52 weeks.

Over that withdrawal period, mean weight change was −5.5% in the group that continued and +14.0% in the group switched to placebo, a difference of 19.4 percentage points (95% CI −21.2 to −17.7, p<0.001). Measured from the start of the lead-in to week 88, mean reduction was 25.3% with continued treatment and 9.9% after withdrawal.

That is the most direct evidence available on what this class is: the trials describe an ongoing treatment rather than a fixed course with a finish line. How long anyone stays on it, at what dose, and what follows is a clinical decision made with a prescriber.

SURPASS-2: tirzepatide compared with semaglutide

SURPASS-2 is the head-to-head trial of these two molecules in adults with type 2 diabetes; SURMOUNT-5, in the next section, is the head-to-head in adults with obesity and no diabetes. Over 40 weeks in 1,879 adults with type 2 diabetes inadequately controlled on metformin, all three tirzepatide doses produced a larger mean HbA1c reduction than semaglutide 1.0 mg weekly, which was the highest semaglutide dose approved for type 2 diabetes at the time the trial ran.

Arm (once weekly)	Mean HbA1c change at 40 weeks	Mean body-weight change at 40 weeks
Tirzepatide 5 mg	−2.01%	−7.6 kg
Tirzepatide 10 mg	−2.24%	−9.3 kg
Tirzepatide 15 mg	−2.30%	−11.2 kg
Semaglutide 1.0 mg	−1.86%	−5.7 kg

Each dose was tested first for noninferiority and then for a greater HbA1c reduction than the comparator. The greater-reduction test was met at p<0.001 for the 10 mg and 15 mg arms; for the 5 mg arm the estimated difference was −0.15 percentage points (95% CI −0.28 to −0.03) at p=0.02. That distinction is worth keeping, because a single "p<0.001 across all doses" summary — common in secondary coverage — overstates what the lowest dose showed.

Two caveats sit on top of the table. The comparator dose is dated — higher semaglutide doses were approved after this trial was designed. And SURPASS-2 reported HbA1c and body weight, not inflammatory markers or cardiovascular events, so claims that one molecule outperforms the other on hsCRP or IL-6 rest on no published head-to-head trial. The semaglutide page covers that molecule's own evidence.

SURMOUNT-5: the same comparison without diabetes

SURMOUNT-5 repeated the comparison in obesity rather than diabetes: 751 adults with obesity and without type 2 diabetes, over 72 weeks, at maximum tolerated doses — tirzepatide 10 or 15 mg against semaglutide 1.7 or 2.4 mg.

Mean weight change at week 72 was −20.2% on tirzepatide and −13.7% on semaglutide, or −22.8 kg against −15.0 kg. Waist circumference fell 18.4 cm versus 13.0 cm. At least 30% of body weight was lost by 19.7% of the tirzepatide group and 6.9% of the semaglutide group.

Two design features are worth knowing before weighing that result. The trial was open-label, so neither participants nor investigators were blinded to which medicine they were on. And it compared maximum tolerated doses rather than one fixed dose in each arm, which reflects how the medicines are actually titrated but makes the comparison a comparison of strategies rather than of milligrams.

Side effects, dose escalation, and why people stopped

The dominant adverse effects across the programme were gastrointestinal — nausea, diarrhoea and vomiting — mostly mild to moderate, and concentrated during dose escalation rather than maintenance. Discontinuation for adverse events ran at 4.3–7.1% across tirzepatide arms and 2.1–2.6% on placebo.

Precise incidence figures vary by trial, dose and population, and the ranges most often quoted in secondary sources — nausea in roughly 20–30% of participants, diarrhoea in 15–20%, vomiting in 5–10% — do not trace back to a single published trial, so treat them as approximate rather than as trial results.

The nausea has a known mechanism: delayed gastric emptying driven by GLP-1 receptor activation, plus direct activation of GLP-1-receptor-expressing neurons in the area postrema, the brainstem's emetic centre. Dosing protocols are built around it — the weekly ladder steps 2.5 → 5 → 7.5 → 10 → 12.5 → 15 mg with about 4 weeks at each step, so reaching the top dose takes roughly five months. Whether an individual escalates at all, and how fast, is a clinical decision.

What SURPASS-CVOT found about cardiovascular outcomes

SURPASS-CVOT reported in the New England Journal of Medicine in December 2025. In more than 13,000 adults with type 2 diabetes and established atherosclerotic cardiovascular disease, followed for a median of about four years, three-point major adverse cardiovascular events occurred in 12.2% of participants on tirzepatide and 13.1% of those on dulaglutide (hazard ratio 0.92). The trial met noninferiority at p=0.003 but missed superiority at p=0.09 — so it did not establish an advantage over dulaglutide on the primary endpoint. All-cause mortality was lower in the tirzepatide group, a difference driven by fewer non-cardiovascular deaths.

Older coverage still describes this trial as ongoing, with results expected in 2024–2025. It has reported, and noninferiority against an active comparator is a different statement from added cardiovascular benefit.

Separately, risk-factor changes have been reported across SURPASS-1 through -5: systolic blood-pressure reduction ranged from −2.8 to −12.6 mmHg, with a placebo- or comparator-adjusted difference of −1.3 to −11.5 mmHg. Figures circulating for triglyceride reduction (20–30%) and hsCRP reduction (30–40%) are not traceable to a published post-hoc analysis. Claims that reduced epicardial fat volume or arterial stiffness prove a vascular effect independent of weight loss are hypotheses, not findings.

Liver fat: what the imaging data show

Published hepatic data for tirzepatide come from magnetic-resonance imaging, not liver biopsy. In an MRI sub-study of SURPASS-3, in adults with type 2 diabetes, pooled 10 mg and 15 mg dosing reduced liver-fat content measured by MRI-PDFF by 8.09 percentage points from a baseline of 15.71% at week 52, compared with insulin degludec — roughly a halving in relative terms. Widely repeated figures of "30–40% liver fat reduction" match neither the absolute nor the relative published result.

Liver-fat content is the measurement that defines metabolic dysfunction-associated steatotic liver disease, or MASLD — the condition renamed in 2023 from non-alcoholic fatty liver disease (NAFLD). That is why these trials track it: excess hepatic fat is the entry point to the whole spectrum, and in people with type 2 diabetes it is common. Reducing measured liver fat and changing the course of the disease are different endpoints, though, and only the first has been reported for tirzepatide.

The mechanism is well characterised in preclinical models: reduced de novo lipogenesis through downregulation of SREBP-1c and fatty acid synthase, more fatty-acid oxidation through PPARα and carnitine palmitoyltransferase-1, and less free-fatty-acid flux to the liver as adipose insulin sensitivity improves. Systemic insulin sensitisation also lowers hepatic glucose production and compensatory hyperinsulinaemia. No trial with a liver-biopsy endpoint has been published for this molecule, so fibrosis outcomes remain unestablished.

Where tirzepatide sits among incretin medicines

Against single-receptor GLP-1 medicines, the dual agonist produced larger mean reductions in HbA1c and weight in both published head-to-head trials — SURPASS-2 in type 2 diabetes and SURMOUNT-5 in obesity. Indirect comparisons — often quoted as a 0.3–0.5 percentage-point HbA1c advantage and 3–5 kg of extra weight loss against liraglutide, semaglutide or dulaglutide — come from network meta-analyses that are rarely named and draw on different trial sets, so those bands are indicative at best. Two other repeated figures deserve flagging: that appetite suppression accounts for 60–70% of the weight change, and that GIP sensitivity recovers over 12–24 weeks of treatment. Neither has a published study behind it.

Beyond dual agonism, the next class adds glucagon-receptor activity. In a phase 2 trial of retatrutide, a triple GLP-1/GIP/glucagon agonist, 338 adults reached a mean 24.2% weight reduction at 48 weeks on the 12 mg dose. Glucagon adds hepatic fatty-acid oxidation and energy expenditure, but it narrows the therapeutic window — raised blood glucose and higher heart rate become titration constraints. Research also continues on monthly or quarterly dosing, oral delivery with permeation enhancers or carrier peptides, implantable depots, and tissue-selective targeting; combinations with SGLT2 inhibitors, leptin sensitisers and mitochondrial uncouplers are discussed without published outcome data.

The areas still being studied

Beta-cell preservation and cognition are the two open questions most often raised, and both rest on animal data. Long-term exposure preserved beta-cell mass and function in diabetic animal models through anti-apoptotic signalling and increased beta-cell replication; human confirmation remains limited. In fat tissue, animal and cell studies show upregulated lipolysis, fatty-acid oxidation and thermogenic programming in white and brown adipocytes, with enhanced insulin-stimulated Akt phosphorylation and altered expression of PPARα, PPARγ, PGC-1α, C/EBPα and SREBP1. In the brain, GLP-1 receptor activation is protective against amyloid-beta toxicity, oxidative stress and neuroinflammation in preclinical models of cognitive decline — but human cognitive data for tirzepatide are limited, and improving metabolic risk factors linked to dementia is not the same as showing a cognitive benefit.

How Promise handles tirzepatide

Promise dispenses tirzepatide as a compounded formulation, which is not the same as an FDA-approved product: the medication offered here is not FDA-approved. Compounded medications are prepared by a licensed pharmacy for an individual patient rather than manufactured as a branded product, and that difference is worth understanding before starting.

Every request runs through the same gate. A licensed provider in Promise's prescriber network reviews the intake questionnaire and medical history, prescribes only if the medication is clinically appropriate, and may decline — not everyone qualifies. Dosing, escalation pace and monitoring are decided in that review, not chosen from a menu. The intake form for compounded tirzepatide is specific to this medication, and the wider metabolic support and fat loss category page covers the other options a provider may consider.

This article is for informational purposes and is not medical advice. Trial figures are averages from the study populations described, and individual results differ.

References

Frías JP, Davies MJ, Rosenstock J, et al. Tirzepatide versus Semaglutide Once Weekly in Patients with Type 2 Diabetes. N Engl J Med. 2021;385(6):503-515. doi:10.1056/NEJMoa2107519. https://pubmed.ncbi.nlm.nih.gov/34170647/
Jastreboff AM, Aronne LJ, Ahmad NN, et al. Tirzepatide Once Weekly for the Treatment of Obesity. N Engl J Med. 2022;387(3):205-216. doi:10.1056/NEJMoa2206038. https://pubmed.ncbi.nlm.nih.gov/35658024/
Garvey WT, Frias JP, Jastreboff AM, et al. Tirzepatide once weekly for the treatment of obesity in people with type 2 diabetes (SURMOUNT-2): a double-blind, randomised, multicentre, placebo-controlled, phase 3 trial. Lancet. 2023;402(10402):613-626. doi:10.1016/S0140-6736(23)01200-X. https://pubmed.ncbi.nlm.nih.gov/37385275/
Willard FS, Douros JD, Gabe MB, et al. Tirzepatide is an imbalanced and biased dual GIP and GLP-1 receptor agonist. JCI Insight. 2020;5(17):e140532. doi:10.1172/jci.insight.140532. https://pubmed.ncbi.nlm.nih.gov/32730231/
Sun B, Willard FS, Feng D, et al. Structural determinants of dual incretin receptor agonism by tirzepatide. Proc Natl Acad Sci U S A. 2022;119(13):e2116506119. doi:10.1073/pnas.2116506119
El K, Douros JD, Willard FS, et al. The incretin co-agonist tirzepatide requires GIPR for hormone secretion from human islets. Nat Metab. 2023;5(6):945-954. doi:10.1038/s42255-023-00811-0. https://pubmed.ncbi.nlm.nih.gov/37277609/
Samms RJ, Christe ME, Collins KA, et al. GIPR agonism mediates weight-independent insulin sensitization by tirzepatide in obese mice. J Clin Invest. 2021;131(12):e146353. doi:10.1172/JCI146353. https://pubmed.ncbi.nlm.nih.gov/34003802/
Borner T, Geisler CE, Fortin SM, et al. GIP Receptor Agonism Attenuates GLP-1 Receptor Agonist-Induced Nausea and Emesis in Preclinical Models. Diabetes. 2021;70(11):2545-2553. doi:10.2337/db21-0459. https://pubmed.ncbi.nlm.nih.gov/34380697/
Nicholls SJ, Pavo I, Bhatt DL, et al. Cardiovascular Outcomes with Tirzepatide versus Dulaglutide in Type 2 Diabetes (SURPASS-CVOT). N Engl J Med. 2025;393(24):2409-2420. doi:10.1056/NEJMoa2505928. https://pubmed.ncbi.nlm.nih.gov/41406444/
Aronne LJ, Sattar N, Horn DB, et al. Continued Treatment With Tirzepatide for Maintenance of Weight Reduction in Adults With Obesity: The SURMOUNT-4 Randomized Clinical Trial. JAMA. 2024;331(1):38-48. doi:10.1001/jama.2023.24945. https://pubmed.ncbi.nlm.nih.gov/38078870/
Aronne LJ, Horn DB, le Roux CW, et al. Tirzepatide as Compared with Semaglutide for the Treatment of Obesity (SURMOUNT-5). N Engl J Med. 2025;393(1):26-36. doi:10.1056/NEJMoa2416394. https://pubmed.ncbi.nlm.nih.gov/40353578/

Common questions

What makes tirzepatide different from taking separate GLP-1 and GIP drugs?

A single molecule delivers a fixed ratio of GIP-receptor to GLP-1-receptor activation that co-administering two drugs cannot reproduce: tirzepatide is roughly equipotent with native GIP at the GIP receptor, about five-fold weaker than native GLP-1 at the GLP-1 receptor, and biased in how it signals there. Because one albumin-binding modification governs both activities, the two effects rise and fall together rather than clearing at different rates.

Why is tirzepatide injected only once a week?

Three design features extend its half-life to about 5 days. A C20 fatty diacid attached to a lysine residue binds reversibly to albumin, creating a slow-release reservoir in the circulation. Two Aib substitutions sterically block DPP-4, the enzyme that clears native incretins in minutes. Further substitutions resist other proteases and slow renal clearance. Native GLP-1 lasts about 2 minutes and native GIP about 7.

How does tirzepatide compare with semaglutide?

In SURPASS-2, over 40 weeks in 1,879 adults with type 2 diabetes on metformin, HbA1c fell 2.01, 2.24 and 2.30 percentage points on tirzepatide 5, 10 and 15 mg versus 1.86 points on semaglutide 1.0 mg weekly; mean weight change was −7.6, −9.3 and −11.2 kg versus −5.7 kg. The comparator dose reflects what was approved for type 2 diabetes when the trial ran. Mechanistically, tirzepatide also engages the GIP receptor.

Why does tirzepatide cause nausea?

Nausea comes from the GLP-1 arm: delayed gastric emptying via vagal afferent signalling, plus direct activation of GLP-1-receptor-expressing neurons in the area postrema, the brainstem's emetic centre. In the published trials it clusters during dose escalation rather than maintenance, which is why protocols hold each step for about 4 weeks.

Does having type 2 diabetes change the weight results?

Yes, substantially. At the same 15 mg dose and the same 72-week duration, mean weight reduction was 20.9% in SURMOUNT-1 participants without type 2 diabetes and 14.7% in SURMOUNT-2 participants who had it. Any single percentage quoted without its population attached is ambiguous.

How long does it take for a weekly dose to reach a steady level?

Plasma concentrations reach steady state after about 4 weeks on a given weekly dose, with minimal further accumulation. Reaching 15 mg through the standard ladder — 2.5, 5, 7.5, 10, 12.5, 15 mg at roughly 4-week intervals — takes about five months, and the readouts discussed here were measured at 40 and 72 weeks.

Can tirzepatide cause low blood sugar?

Insulin secretion driven by the GLP-1 and GIP receptors is glucose-dependent: it tapers as plasma glucose returns toward normal, so hypoglycaemia risk from tirzepatide by itself is low even at higher doses. That changes alongside insulin or a sulfonylurea, which is one reason the full medication list matters at intake.

What did the cardiovascular outcome trial find?

SURPASS-CVOT, published in the *New England Journal of Medicine* in December 2025, followed more than 13,000 adults with type 2 diabetes and established atherosclerotic cardiovascular disease for a median of about four years. Three-point major adverse cardiovascular events occurred in 12.2% on tirzepatide versus 13.1% on dulaglutide (hazard ratio 0.92), meeting noninferiority at p=0.003 but missing superiority at p=0.09 — so it did not establish an advantage on the primary endpoint. All-cause mortality was lower on tirzepatide, driven by fewer non-cardiovascular deaths.

Does tirzepatide reduce liver fat?

In an MRI sub-study of SURPASS-3, in adults with type 2 diabetes, pooled 10 mg and 15 mg dosing lowered liver-fat content measured by MRI-PDFF by 8.09 percentage points from a 15.71% baseline at week 52, compared with insulin degludec. Liver fat is the defining measurement in MASLD — metabolic dysfunction-associated steatotic liver disease, formerly called NAFLD. That evidence is imaging-based; no trial using liver biopsy as an endpoint has been published for this molecule, so effects on fibrosis are unestablished.

What happened when people stopped taking tirzepatide in the trials?

SURMOUNT-4 tested exactly that. After 36 open-label weeks in which 670 participants averaged 20.9% weight reduction, those randomised to continue had a further mean change of −5.5% over the next 52 weeks, while those switched to placebo averaged +14.0% — a 19.4 percentage-point difference. From the start of the lead-in to week 88, mean reduction was 25.3% with continued treatment and 9.9% after withdrawal. The trial data describe an ongoing treatment, not a fixed course.

Why was GIP once dismissed as a diabetes target?

Injected GIP produces a blunted insulin response in people with type 2 diabetes compared with healthy controls, attributed to receptor downregulation and desensitisation, so the pathway was written off for years. Concurrent GLP-1 receptor activation appears to restore that responsiveness; the mechanism is unclear, with heterodimerisation, shared signalling scaffolds and epigenetic upregulation all proposed.

How do triple agonists compare with tirzepatide?

Triple agonists add glucagon-receptor activity. In a phase 2 trial of retatrutide, 338 participants had a mean 24.2% weight reduction at 48 weeks on 12 mg — against the 20.9% seen at 72 weeks in SURMOUNT-1, though durations and populations differ and no head-to-head exists. Glucagon activity also narrows the therapeutic window, with raised blood glucose and heart rate as titration constraints.

Is the compounded tirzepatide Promise dispenses the same as the branded medication?

No. FDA-approved tirzepatide products exist, but the compounded formulation offered here is not FDA-approved. Compounded medications are prepared by a licensed pharmacy for an individual patient rather than manufactured under a branded approval, and a prescribing provider covers what that means at intake.