Semaglutide vs Tirzepatide for Weight Loss: How They Differ
Semaglutide vs tirzepatide comes down to locks. Semaglutide turns on one receptor, GLP-1, while tirzepatide is a single molecule that turns on two, GIP and GLP-1.
Semaglutide is sold as Ozempic, Rybelsus, Ozempic tablets and Wegovy. Tirzepatide is sold as Mounjaro and Zepbound. In two head-to-head trials, people on tirzepatide lost more weight on average, 20.2% against 13.7% in the weight trial. Both trials were open label and paid for by Eli Lilly. Neither can say that the second lock is the reason.
Key facts
Semaglutide: A copy of the gut hormone GLP-1 from Novo Nordisk. It turns on the GLP-1 receptor only. Brands: Ozempic, Rybelsus, Ozempic tablets, Wegovy.
Tirzepatide: A molecule from Eli Lilly built on a second gut hormone, GIP. It turns on both the GIP and GLP-1 receptors. Brands: Mounjaro, Zepbound.
Head to head: Weight fell 20.2% on tirzepatide vs 13.7% on semaglutide over 72 weeks (SURMOUNT-5). Open label and funded by Lilly.
Status on 8 November 2026: All seven brands are US prescription medicines, and the FDA has declared both shortages over.
Sources: Ozempic label, FDA, May 2026; Mounjaro label, FDA, August 2026; SURMOUNT-5, New England Journal of Medicine 2025; Drugs@FDA records for all seven brands; FDA updates on the GLP-1 shortages
What is the difference between semaglutide and tirzepatide?
The main difference is how many locks each one opens. On this channel a hormone is a key and its receptor is a lock. Semaglutide fits one lock. Tirzepatide fits two.
Semaglutide is a lab-made form of GLP-1, a hormone the gut releases after eating. Its chain of amino acids matches 94% of human GLP-1, and yeast builds that chain. The Ozempic label says it binds to the GLP-1 receptor and turns it on, just as the natural hormone does. We covered the tablet form in our oral semaglutide explainer.
Tirzepatide starts from a different gut hormone, GIP (glucose-dependent insulinotropic polypeptide). Its label says it is based on the GIP sequence. A building block called Aib is swapped in at spots 2 and 13. Even so, this one molecule acts as a key for the GIP receptor as well as the GLP-1 receptor. Our animated look at how tirzepatide works follows it into both locks.
Both are peptides, so both come as shots, apart from the semaglutide pills. That is why vial math tools like the semaglutide reconstitution calculator and the tirzepatide reconstitution calculator exist on this site.
Sources: Ozempic label, FDA, May 2026; Mounjaro label, FDA, August 2026; Rybelsus and Ozempic tablets label, FDA, January 2026
Ozempic vs Mounjaro, Wegovy vs Zepbound: which brand is which?
Ozempic vs Mounjaro is semaglutide against tirzepatide for type 2 diabetes. Wegovy vs Zepbound is the same pair of drugs approved for weight. Each brand name stands for one drug with one set of FDA-approved jobs, so there are seven brand listings for two molecules.
| Brand | Drug | FDA-approved uses | First approved |
|---|---|---|---|
| Ozempic (shot) | Semaglutide | Blood sugar in adults with type 2 diabetes; fewer heart attacks, strokes and heart deaths in those with heart disease; slower kidney decline in those with chronic kidney disease. | December 2017 |
| Rybelsus and Ozempic tablets | Semaglutide | Blood sugar in adults with type 2 diabetes; fewer major heart events in those at high risk. One label covers both pills. | September 2019 (Rybelsus) |
| Wegovy (shot) | Semaglutide | Long-term weight reduction in adults and children 12 and older with obesity, and adults who are overweight with a weight-linked condition; fewer major heart events in adults with heart disease and excess weight; MASH liver disease with scarring, under accelerated approval. | June 2021 |
| Wegovy pill | Semaglutide | Long-term weight reduction in adults; fewer major heart events in adults with heart disease and excess weight. | December 2025 |
| Mounjaro | Tirzepatide | Blood sugar in adults and children 10 and older with type 2 diabetes; fewer major heart events in high-risk adults with type 2 diabetes (added August 2026). | May 2022 |
| Zepbound | Tirzepatide | Long-term weight reduction in adults with obesity, or overweight with a weight-linked condition; obstructive sleep apnea, moderate to severe, in adults who also have obesity (added December 2024). | November 2023 |
Semaglutide reached the US first. Ozempic was approved on 5 December 2017, about four and a half years before Mounjaro on 13 May 2022. The name Ozempic tablets was approved in January 2026 for a reworked semaglutide pill that shares one label with Rybelsus.
Neither diabetes brand is approved for weight loss. For weight, the matching pair is Wegovy and Zepbound. Zepbound picked up a second job in December 2024: treating moderate to severe obstructive sleep apnea when a person also has obesity.
Sources: Ozempic label, FDA, May 2026; Rybelsus and Ozempic tablets label, FDA, January 2026; Wegovy shot and pill label, FDA, June 2026; Mounjaro label, FDA, August 2026; Zepbound label, FDA, August 2026; Drugs@FDA records for all seven brands
How do semaglutide and tirzepatide differ in the body?
They differ in four main ways: the locks, the starting hormone, the fatty tail and the half-life. The table adds size and maker.
| Feature | Semaglutide | Tirzepatide |
|---|---|---|
| Locks it turns on | One: the GLP-1 receptor | Two: the GIP receptor and the GLP-1 receptor |
| Hormone it is built from | GLP-1, with a chain 94% the same as the human hormone | GIP, with a few building blocks swapped (Aib at spots 2 and 13) |
| Fatty tail that grips albumin | 18-carbon tail; more than 99% rides on albumin | 20-carbon tail; 99% rides on albumin |
| Half-life (time for half to be gone) | About 1 week | About 5 days |
| Size | 4,113.58 g/mol | 4,813.53 Da |
| Maker | Novo Nordisk | Eli Lilly |
Why both last for days. Both drugs carry a fatty acid tail that grips albumin, a carrier protein in the blood. The Ozempic label says this binding slows how fast the kidneys clear semaglutide. It also shields the drug from breakdown. The Mounjaro label says the tail stretches the half-life of tirzepatide. Semaglutide also has a change at spot 8 that blocks DPP-4, the enzyme that cuts natural GLP-1 apart.
Tirzepatide has the longer tail. Semaglutide uses an 18-carbon fatty acid, and tirzepatide uses a 20-carbon one. Yet tirzepatide has the shorter half-life: about five days against about a week. So a longer tail does not by itself mean a longer stay.
Sources: Ozempic label, FDA, May 2026; Mounjaro label, FDA, August 2026
What did the head-to-head trials find?
Two big trials gave people either tirzepatide or semaglutide, and tirzepatide came out ahead on average in both. Eli Lilly, which makes tirzepatide, funded both. Both were open label, which means everyone knew which drug they were on.
| Trial | Who took part | Length | Main result |
|---|---|---|---|
| SURPASS-2 | 1,879 adults with type 2 diabetes, already on metformin | 40 weeks | A1C fell 2.01 to 2.30 points on tirzepatide vs 1.86 on semaglutide; 1.9 to 5.5 kg more weight lost on tirzepatide |
| SURMOUNT-5 | 751 adults with obesity, or overweight plus a related condition, no diabetes | 72 weeks | Weight fell 20.2% on tirzepatide vs 13.7% on semaglutide; waist shrank 18.4 cm vs 13.0 cm |
SURPASS-2 was about blood sugar. A1C is a blood test that shows average sugar over about three months. It started near 8.3%. It fell further in all three tirzepatide groups than in the single semaglutide group. The authors called every tirzepatide group superior.
SURMOUNT-5 was about weight, in adults who had obesity or carried extra weight with a related health problem but no diabetes. Each person was stepped up to the highest level of their drug they could tolerate. The authors concluded that tirzepatide was superior for weight and waist size at week 72.
What these trials cannot tell you. They compared whole medicines. Tirzepatide differs from semaglutide in more than the GIP lock. So the trials cannot show that the second lock causes the gap. Open label designs and maker funding are common in drug trials, but they are worth knowing when you weigh the result.
Sources: SURPASS-2, New England Journal of Medicine 2021; SURMOUNT-5, New England Journal of Medicine 2025; SURMOUNT-5 results on ClinicalTrials.gov
Why can you not just compare the separate trials?
Separate trials used different people, so their numbers do not line up neatly. The main weight trial for each drug compared it with a dummy shot (placebo), not with the other drug.
In STEP 1, 1,961 adults without diabetes lost 14.9% of their weight on semaglutide over 68 weeks, against 2.4% on placebo. In SURMOUNT-1, 2,539 adults without diabetes lost 15.0% to 20.9% across three tirzepatide groups over 72 weeks, against 3.1% on placebo. Novo Nordisk funded the first and Eli Lilly the second.
The trials differ in length, starting weight and who signed up, and the placebo groups did not lose the same amount. That is why a head-to-head trial like SURMOUNT-5 matters. Both drugs were given side by side to one group of people over one stretch of time.
Sources: STEP 1, New England Journal of Medicine 2021; SURMOUNT-1, New England Journal of Medicine 2022; SURMOUNT-5, New England Journal of Medicine 2025
Do people who quit a trial still count?
In SURMOUNT-5, yes. The trial plan is posted on ClinicalTrials.gov. It says the main count includes people whether or not they stopped their drug, for any reason. This is called a modified treatment-regimen estimand. It answers a real-world question: what happens to a group told to start this drug, including those who drop off?
The registry shows how many dropped off. In each group, 319 people finished the trial: 319 of 375 on tirzepatide and 319 of 376 on semaglutide.
An average hides a spread. The registry also lists how many people reached each level of weight loss. These figures count only people who were measured at the end. So they run higher than figures that count everyone who started.
| Weight lost | Tirzepatide | Semaglutide |
|---|---|---|
| At least 10% of body weight | 87.7% | 66.7% |
| At least 15% | 71.7% | 45.0% |
| At least 20% | 55.0% | 31.1% |
| At least 25% | 36.5% | 18.6% |
| At least 30% | 23.0% | 8.2% |
So roughly a third on tirzepatide lost at least a quarter of their weight. On semaglutide it was about a fifth. Others lost far less. These are group results, not a promise for anyone.
Sources: SURMOUNT-5 statistical analysis plan; SURMOUNT-5 results on ClinicalTrials.gov
Is tirzepatide better than semaglutide?
On average weight loss and blood sugar in two trials, tirzepatide did better. That is not the same as better for a given person, and a few limits matter.
- SURPASS-2 tested three tirzepatide levels against one semaglutide level.
- Both trials were open label and funded by the maker of tirzepatide.
- Results spread widely around each average, as the table above shows.
- No trial has compared the two drugs on heart attacks, strokes or deaths.
The heart trials point different ways. SUSTAIN-6 tested semaglutide against placebo in 3,297 adults with type 2 diabetes. Major heart events were less common (hazard ratio 0.74). But eye problems from diabetic retinopathy were more common (hazard ratio 1.76). In the Wegovy heart trial of 17,604 adults with heart disease and excess weight, the hazard ratio was 0.80 against placebo. Tirzepatide was tested against dulaglutide, another GLP-1 drug, in SURPASS-CVOT with 13,299 adults. It was not worse (hazard ratio 0.92), but it was not shown to be better either.
Whether either drug suits someone depends on their health, other medicines and history, which is a prescriber's call. Our medical review policy explains how we check trial and label facts before they appear here.
Sources: SURPASS-2, New England Journal of Medicine 2021; SURMOUNT-5, New England Journal of Medicine 2025; SURMOUNT-5 results on ClinicalTrials.gov; SUSTAIN-6, New England Journal of Medicine 2016; Wegovy shot and pill label, FDA, June 2026; Mounjaro label, FDA, August 2026
What are the side effects, and do they share a warning?
The side effects look much alike, and so does the warning. Both drugs lead with the gut. The Ozempic label lists nausea, vomiting, diarrhea, belly pain and constipation as the most common. The Mounjaro label lists nausea, diarrhea, lower appetite, vomiting, constipation, indigestion and belly pain.
In SURPASS-2, nausea hit 17% to 22% on tirzepatide and 18% on semaglutide. Diarrhea ran 13% to 16% against 12%, and vomiting 6% to 10% against 8%. Serious side effects were reported in 5% to 7% on tirzepatide and 3% on semaglutide. In SURMOUNT-5, gut problems were the most common in both groups, mostly mild to moderate and mostly during the step-up phase. The registry counts serious side effects in 18 of 374 people on tirzepatide and 13 of 376 on semaglutide.
The shared boxed warning. In rodents, semaglutide caused thyroid C-cell tumors, and in rats so did tirzepatide. Nobody knows yet whether either does this in people. So neither label allows use in people whose own history, or whose family history, includes medullary thyroid cancer. People with MEN 2 (multiple endocrine neoplasia type 2) are ruled out too.
The other warnings match too. Both drug families warn about pancreatitis and gallbladder disease. They warn about low blood sugar if combined with insulin or certain other diabetes medicines, and kidney damage after dehydration. They also flag serious stomach and bowel reactions, allergy, and inhaling stomach contents during anesthesia. All four shot labels also warn that diabetic eye disease (retinopathy) can get worse. The two tirzepatide labels list that section among their August 2026 changes.
The weight labels also say not to combine either drug with another GLP-1 medicine. Moving from one drug to the other is a separate topic. It is covered in our guide to switching from semaglutide to tirzepatide, and this page does not cover it.
Sources: Ozempic label, FDA, May 2026; Mounjaro label, FDA, August 2026; Zepbound label, FDA, August 2026; Wegovy shot and pill label, FDA, June 2026; SURPASS-2, New England Journal of Medicine 2021; SURMOUNT-5, New England Journal of Medicine 2025; SURMOUNT-5 results on ClinicalTrials.gov
Are semaglutide and tirzepatide FDA approved?
Yes. We checked Drugs@FDA on 8 November 2026. It listed every brand on this page as a prescription medicine: Ozempic, Rybelsus, Ozempic tablets, the Wegovy shot and pill, Mounjaro and Zepbound. One older Ozempic product listing is marked discontinued.
The FDA has also declared both US shortages over. It ruled the tirzepatide shortage resolved on 19 December 2024, after taking a second look at an October 2024 decision. The semaglutide shortage followed on 21 February 2025.
Sources: Drugs@FDA records for all seven brands; FDA updates on the GLP-1 shortages
What else do people ask about semaglutide vs tirzepatide?
What is the difference between semaglutide and tirzepatide?+
Semaglutide switches on one receptor, the GLP-1 receptor, and is built from the GLP-1 hormone. Tirzepatide switches on two, the GIP and GLP-1 receptors, and is built from the GIP hormone. Both carry a fatty tail that rides on albumin in the blood, so both last for days. Semaglutide lasts about a week and tirzepatide about five days. Novo Nordisk makes semaglutide and Eli Lilly makes tirzepatide.
Is tirzepatide way better than semaglutide?+
In both head-to-head trials, the tirzepatide group did better on average. In SURMOUNT-5, weight fell 20.2% against 13.7% over 72 weeks. In SURPASS-2, A1C fell 2.01 to 2.30 points against 1.86. Both trials were open label and paid for by Eli Lilly, which makes tirzepatide, and SURPASS-2 tested only one semaglutide level. Averages also hide a wide spread, and no trial has compared the two on heart outcomes. So the trials show a group difference, not which drug suits one person.
Can someone lose more weight on semaglutide than on tirzepatide?+
Yes, some people do. The averages favored tirzepatide, but the two groups overlapped a lot. In the SURMOUNT-5 registry results, 18.6% of people on semaglutide lost at least a quarter of their weight. Meanwhile 12.3% of people on tirzepatide lost less than a tenth. A group average says nothing certain about one person.
Do you lose more muscle on semaglutide or tirzepatide?+
The head-to-head trials do not answer this. Neither SURMOUNT-5 nor SURPASS-2 lists muscle or lean mass among its registered outcomes. None of the four shot labels we read reports body composition results either. So these sources cannot say which drug costs more muscle.
Mounjaro vs Ozempic: which is which?+
Mounjaro is tirzepatide and Ozempic is semaglutide. Both are US shots for type 2 diabetes. Both now also carry a heart-risk use for some adults with type 2 diabetes. Ozempic adds a kidney use. Neither is approved for weight loss: the weight brands are Zepbound (tirzepatide) and Wegovy (semaglutide).
Ozempic vs Mounjaro: which lowered blood sugar more?+
SURPASS-2 put the two drugs side by side in type 2 diabetes. A1C fell 2.01 to 2.30 points across three tirzepatide groups against 1.86 points on semaglutide over 40 weeks. All 1,879 adults were already on metformin. The authors reported every tirzepatide group as better than semaglutide on this measure.
Zepbound vs Wegovy: what did the head-to-head trial find?+
SURMOUNT-5 compared the drugs inside Zepbound and Wegovy in 751 adults without diabetes. After 72 weeks, weight fell 20.2% on tirzepatide and 13.7% on semaglutide, and waist size fell 18.4 cm against 13.0 cm. Everyone also had diet and activity support, and each person was stepped up as far as they could tolerate.
Why did tirzepatide lead to more weight loss?+
Nobody can say for sure. Tirzepatide turns on a second lock, GIP. But it also has a different backbone and a different fatty tail. The head-to-head trials tested whole medicines, not the GIP lock on its own, so they cannot show that GIP explains the gap.
Do semaglutide and tirzepatide have the same side effects?+
Mostly, yes. Both labels list gut problems first: nausea, diarrhea, vomiting, constipation and belly pain. In SURPASS-2, nausea hit 17% to 22% on tirzepatide and 18% on semaglutide. Serious side effects were reported in 5% to 7% against 3%. Both carry the same boxed warning about thyroid C-cell tumors seen in rodents.
Can semaglutide and tirzepatide be used together?+
The weight labels say no. The Wegovy label advises against using it with other semaglutide products or any other GLP-1 drug. The Zepbound label says the same for tirzepatide products and GLP-1 drugs. No approved label describes using the two together.
Are semaglutide and tirzepatide FDA approved?+
Yes. On 8 November 2026, Drugs@FDA listed all seven brands as prescription medicines: Ozempic, Rybelsus, Ozempic tablets, the Wegovy shot and pill, Mounjaro and Zepbound. The FDA also declared both US shortages over, tirzepatide on 19 December 2024 and semaglutide on 21 February 2025.
How long do semaglutide and tirzepatide last in the body?+
Half-life is the time for half of the drug to be gone. The labels put it at about one week for semaglutide and about five days for tirzepatide. Both stay around because a fatty tail lets them ride on albumin, a carrier protein in the blood. That slows how fast the body clears them.
Can you lose weight with oral semaglutide?+
One semaglutide pill is approved for it. The FDA cleared the Wegovy pill in December 2025, and its label covers long-term weight reduction in adults, plus a lower chance of heart attack, stroke or heart-related death for adults who carry excess weight and already have heart disease. Rybelsus and Ozempic tablets sit on a separate label for type 2 diabetes and heart risk, so weight loss is not one of their approved uses. How much anyone loses varies, and only a prescriber can judge if a pill suits them.
Sources: Ozempic label, FDA, May 2026; Mounjaro label, FDA, August 2026; Wegovy shot and pill label, FDA, June 2026; Zepbound label, FDA, August 2026; SURPASS-2, New England Journal of Medicine 2021; SURMOUNT-5, New England Journal of Medicine 2025; Drugs@FDA records for all seven brands; FDA updates on the GLP-1 shortages; Rybelsus and Ozempic tablets label, FDA, January 2026
So what is the difference?
Semaglutide is one key shaped like GLP-1 for one lock. Tirzepatide is one key built on GIP that opens two locks. Both ride on albumin, both share a thyroid warning, and in two Lilly-funded, open label trials tirzepatide had the bigger averages. Why it did is still an open question.
Molecule Mechanics is a YouTube channel of animated explainers on how peptide medicines work and what their trials found. It does not tell anyone what to take. An ElevenLabs AI voice reads the script, the animation is drawn for the channel, and each video lists its sources. This is episode 5. Earlier episodes covered tirzepatide, cagrilintide and oral semaglutide.
Trulicity (dulaglutide), the drug tirzepatide was tested against in its heart trial, has its own Trulicity article. Retatrutide, still experimental, adds a third lock. The retatrutide calculator is the page on this site that Google searchers click most often. If you find a mistake here, our corrections policy says how to tell us.
See every Molecule Mechanics episode
Sources: Molecule Mechanics on YouTube; Mounjaro label, FDA, August 2026
This page is for learning and is not medical advice. It reports what FDA labels and published trials say about semaglutide and tirzepatide. Only a person's own doctor can say if either medicine is right for them.