You started this search because the GLP-1 your friend lost 30 pounds on may not be the one your doctor mentioned first. The names blur together on a screen at 11 p.m.: Ozempic, Wegovy, Mounjaro, Zepbound, semaglutide vs Tirzepatide.
I read every major trial so you do not have to. This article puts semaglutide and Tirzepatide side by side. You will see the head-to-head data, the side effect math, and how to think about your choice in 2026 after the FDA shortage list closed.
Key takeaways
Tirzepatide produced about 6.5 percentage points more weight loss than semaglutide in the only head-to-head trial (SURMOUNT-5, 2025).
Semaglutide is the only GLP-1 with published cardiovascular outcome data showing fewer heart events (SELECT, 2023).
Both drugs are FDA approved for weight management (Wegovy and Zepbound) and type 2 diabetes (Ozempic and Mounjaro).
Side effect profiles overlap heavily. Nausea, fatigue, and constipation are the top three for both medications.
Compounded GLP-1s left the FDA shortage list in 2024, so 2026 access usually means a brand-name prescription through insurance or a telehealth provider.
Here is how I will break this down. First the mechanism difference, then the head-to-head trial that settled the weight loss question, then the side effects, the indication math, and access in 2026. By the end you will know what to ask your prescriber, and why.
Side-by-side at a glance
Important: The clinical trial results cited in this article (STEP, SURMOUNT) studied the FDA-approved branded medications (Wegovy®, Ozempic®, Mounjaro®, Zepbound®). These results do not apply to and cannot be attributed to compounded semaglutide or compounded tirzepatide. Compounded medications are not FDA-approved. Always talk to a licensed physician.
| Attribute | Semaglutide | Tirzepatide |
|---|---|---|
| Drug class | GLP-1 receptor agonist | Dual GIP and GLP-1 receptor agonist |
| Weight management brand | Wegovy | Zepbound |
| Type 2 diabetes brand | Ozempic, Rybelsus (oral) | Mounjaro |
| Average weight loss, head-to-head | 13.7% over 72 weeks | 20.2% over 72 weeks |
| Top weight loss trial | STEP 1 (Wilding 2021) | SURMOUNT-1 (Jastreboff 2022) |
| Heart outcome data | SELECT 2023, 20% fewer heart events | SURPASS-CVOT pending late 2026 |
| FDA approval for weight loss | 2021 | 2023 |
| Dosing | Weekly subcutaneous injection | Weekly subcutaneous injection |
| Top three side effects | Nausea, fatigue, constipation | Nausea, fatigue, constipation |
How they actually work
Semaglutide is a single-target medication. It mimics GLP-1, a hormone your gut releases after meals that tells your brain you are full and slows how fast food leaves your stomach. Wegovy and Ozempic are both semaglutide at different approved doses.
Tirzepatide hits two targets at once. It mimics GLP-1 and GIP, a second gut hormone that may improve how your body uses fat and sugar. Researchers call this drug class a twincretin. Mounjaro and Zepbound are both Tirzepatide.
The dual action is the reason most clinicians I follow expected Tirzepatide to win head-to-head trials. The 2025 SURMOUNT-5 readout confirmed it.
The head-to-head verdict: SURMOUNT-5
SURMOUNT-5 is the only randomized trial that put maximum-tolerated doses of Tirzepatide and semaglutide in the same room for weight loss. Aronne and colleagues published the results in the New England Journal of Medicine in May 2025.
The trial enrolled 751 adults with obesity but without diabetes. Over 72 weeks, the Tirzepatide arm lost an average of 20.2% of starting body weight. The semaglutide arm lost 13.7%.
That gap is about 6.5 percentage points. For a 250-pound adult, that is roughly 16 extra pounds on Tirzepatide. SURMOUNT-1 (Jastreboff 2022) and STEP 1 (Wilding 2021) reported similar numbers in separate trials. SURMOUNT-5 is the first apples-to-apples comparison the GLP-1 field has had.
For type 2 diabetes specifically, SURPASS-2 (Frias 2021) showed Tirzepatide 15mg dropped A1C by 2.30 percentage points versus 1.86 for semaglutide 1mg. Tirzepatide also dropped weight more in that trial.
Side effects: which one is harder on your gut?
Both medications cause nausea, vomiting, diarrhea, and constipation. SURMOUNT-5 reported similar dropout rates near 6% in both arms because of side effects, so neither drug is dramatically harsher on average.
Where Tirzepatide tends to feel rougher is the first 48 hours after a dose escalation. The dual GIP and GLP-1 action seems to amplify the early nausea curve. Many users describe their worst week as week 5, when the dose typically jumps from 5mg to 7.5mg.
Semaglutide’s nausea profile feels more linear. The first dose is the worst dose, and tolerance builds over 4 to 6 weeks for most participants in the STEP trials.
Both medications carry an FDA boxed warning for thyroid tumors based on rodent data. Pancreatitis and gallbladder events are also flagged on both labels. Talk to your doctor if you have a personal or family history of thyroid cancer or pancreatitis.
Diabetes vs weight loss: which one fits your goal?
If your primary goal is type 2 diabetes management, your prescriber will probably check insurance coverage first. Ozempic and Mounjaro are both first-line GLP-1 options for diabetes, and both are usually covered when an A1C target has not been met.
For weight management without diabetes, Zepbound (Tirzepatide) gives you more weight loss on average than Wegovy (semaglutide), based on SURMOUNT-5. But Wegovy has SELECT trial data (Lincoff 2023) showing a 20% reduction in major heart events in adults with established cardiovascular disease. Tirzepatide’s heart outcome trial, SURPASS-CVOT, is expected to read out in late 2026.
So the heuristic I use: if you have known heart disease, Wegovy still has the edge for now. If your goal is the largest possible weight loss, Zepbound is the data-backed pick. That recommendation may shift after SURPASS-CVOT publishes.
Access in 2026: who can get what
Both compounds left the FDA drug shortage list in late 2024. That ended the legal pathway for most 503A pharmacies to mass-compound semaglutide and Tirzepatide.
What is still legal in 2026:
What is no longer legal:
Telehealth still works for both medications when a prescriber can meet your state’s licensing rules. Refills.com leads our prescriber comparison because of insurance coverage, intake speed, and continuity of care across the four brand-name options.
Sarah’s verdict
If I were picking for someone with no cardiovascular history and weight loss as the goal, I would ask about Tirzepatide first. The SURMOUNT-5 numbers are too clean to ignore, and average tolerability tracks close enough.
If I were managing established heart disease while also wanting weight loss, I would ask about semaglutide first, because of the SELECT data. That call may move once SURPASS-CVOT publishes.
If your insurance covers one but not the other, that practical constraint usually wins. Both medications produce results no other prescription class can match in 2026. Switching between them later is a normal conversation to have with your prescriber.
Next Step
See who prescribes Wegovy and Zepbound online
Side-by-side review of the telehealth providers writing real brand-name prescriptions in 2026.
Compare GLP-1 prescribersFrequently asked questions
Is Tirzepatide really better than semaglutide for weight loss?
In the SURMOUNT-5 trial published in 2025, adults on Tirzepatide lost 20.2% of body weight over 72 weeks, while the semaglutide arm lost 13.7%. That is roughly 6.5 percentage points more weight on Tirzepatide, or about 16 pounds for a 250-pound starting weight. Personal response varies. Insurance coverage, side effect tolerance, and your heart history may still tilt the choice.
Can I switch from semaglutide to Tirzepatide?
Yes, switching is common. Most prescribers stop one medication and start the other at a low dose the following week to avoid stacked side effects. Expect to repeat the titration ramp from the starting dose, which usually takes 4 to 8 weeks to reach a maintenance level. Tell your prescriber every dose you took before the switch so the ramp is safe.
What does compounded GLP-1 mean in 2026?
Compounded means a licensed pharmacy custom-makes the medication for one patient with a valid prescription. The 2024 shortage exit closed bulk-compounded GLP-1 access for most patients. In 2026, a 503A pharmacy can still compound semaglutide or Tirzepatide when a clinical reason exists, such as an allergy to a brand-formulation excipient. Most patients now use brand-name Ozempic, Wegovy, Mounjaro, or Zepbound.
Which one is cheaper, Wegovy or Zepbound?
Out-of-pocket costs for Wegovy and Zepbound land in a similar range and rarely decide the choice on their own. Insurance coverage usually does. Many commercial plans cover one but not the other, and Medicare coverage depends on the indication you qualify for. Ask your prescriber to run a benefits check before you commit. Manufacturer savings programs shift the math, so check both brand portals.
Do semaglutide and Tirzepatide cause the same side effects?
The top three are the same: nausea, fatigue, and constipation. SURMOUNT-5 reported similar dropout rates near 6% in both arms because of side effects. Tirzepatide tends to feel rougher around dose escalations, especially the jump from 5mg to 7.5mg. Semaglutide builds tolerance more linearly. Both carry FDA boxed warnings for thyroid tumors, pancreatitis, and gallbladder events.
How long does it take to see weight loss on either drug?
Most adults notice appetite changes within the first week. Visible weight loss usually starts at week 4 to 8 as the dose climbs. The STEP 1 trial showed semaglutide users lost an average of 14.9% of body weight by week 68. SURMOUNT-1 showed Tirzepatide users at the highest dose lost 22.5% by week 72. Patience matters; the curves keep moving.
Can I drink alcohol on semaglutide or Tirzepatide?
Neither label bans alcohol, but most prescribers in the STEP and SURMOUNT trials advised cutting back. Both medications slow stomach emptying, which can intensify alcohol effects on an empty stomach. Many users also report alcohol tasting different or losing its appeal. One drink with a meal is the common middle ground for people staying social without spiking nausea.
Important disclosures
peptides.io is an editorial review site. We do not sell, prescribe, or fill any peptide. Articles on this site include affiliate links to telehealth partners such as Refills.com. We may earn a commission when you book a consultation, but it never changes how we write or how we score providers. The content here is editorial opinion built from public research, not medical advice. Semaglutide is FDA approved for type 2 diabetes (as Ozempic) and chronic weight management (as Wegovy). Tirzepatide is FDA approved for type 2 diabetes (as Mounjaro) and chronic weight management (as Zepbound). Trial results from STEP 1, SURMOUNT-1, SURMOUNT-5, SURPASS-2, and SELECT reflect supervised brand-name use and may not transfer to compounded or research-channel products. Talk to your doctor before starting, switching, or stopping any GLP-1 medication. Individual results may vary.
Sources
- Wilding JPH et al. Once-Weekly Semaglutide in Adults with Overweight or Obesity (STEP 1). NEJM 2021;384(11):989 to 1002 Source
- Jastreboff AM et al. Tirzepatide Once Weekly for the Treatment of Obesity (SURMOUNT-1). NEJM 2022;387:205 to 216 Source
- Aronne LJ et al. Tirzepatide Compared with Semaglutide for the Treatment of Obesity (SURMOUNT-5). NEJM 2025;392 Source
- Frias JP et al. Tirzepatide versus Semaglutide Once Weekly in Type 2 Diabetes (SURPASS-2). NEJM 2021;385:503 to 515 Source
- Lincoff AM et al. Semaglutide and Cardiovascular Outcomes in Obesity (SELECT). NEJM 2023;389:2221 to 2232 Source
- US Food and Drug Administration. Drug Shortages List, semaglutide and Tirzepatide status updates 2024 to 2026 Source
Important notices & disclaimers
Editorial & medical: This guide is general education, not medical advice. Talk to a licensed clinician before starting, stopping, or changing any medication.
Affiliate disclosure: Peptides.io may earn a commission from links to providers — it never changes what you pay or how we rank them, and never influences our recommendations.
Compounded GLP-1 (FDA): Compounded semaglutide and tirzepatide are not FDA-approved and have not been evaluated by the FDA for safety, effectiveness, or quality. They are not generic versions of, or equivalent to, branded medications such as Ozempic®, Wegovy®, Mounjaro®, or Zepbound®. Clinical-trial results cited here apply only to those branded formulations — not to compounded preparations.
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