Tirzepatide vs Semaglutide Head to Head: Weight Loss Trial Results (October 2026)

01 · The short verdict

Which did better in the head-to-head trial?

Tirzepatide produced greater average weight loss than semaglutide 2.4mg in SURMOUNT-5: 20.2% of body weight versus 13.7% over 72 weeks.¹⁵ That is the headline, and it is a real difference measured in a direct comparison. It is still an average. Some people on semaglutide lose more than some people on tirzepatide.

The same trial also says something the headline hides. Both medicines are effective, licensed treatments. Which one suits you depends on your health profile, tolerance and prescriber advice, not on the headline number alone.¹⁵ If you want the percentage figures broken down further, see our guide to the weight loss percentage comparison.

02 · Side by side

Tirzepatide vs semaglutide at a glance

Only the SURMOUNT-5 rows are a like-for-like comparison.

The threshold rows come from the SURMOUNT-5 results for 751 adults.¹⁵

03 · Choosing

How to decide between them

Start with what the trial can and cannot tell you. It shows that, across 751 adults, tirzepatide gave a larger average loss. It does not tell you how you will respond, how you will tolerate each dose, or what your other medicines and conditions mean for the choice. That is a prescriber conversation.

Practical factors that matter alongside the efficacy figures:

• Your health profile. Existing conditions and current medicines shape which treatment a prescriber will recommend.
• Tolerance. Side effects differ from person to person, and both medicines are stepped up gradually.
• Your goal. A larger average loss matters more if you have a lot of weight to lose; it matters less if a smaller loss would meet your health target.
• Cost. Compare the Mounjaro pen and the Wegovy pen at your likely maintenance dose, not just the starting pen. Prices checked 10 October 2026.
• Prior experience. If one medicine has not suited you, the other may be worth discussing.

You can start a free online consultation, which is reviewed by a GPhC-registered prescriber, who can help you choose between them.

Related guide: Tirzepatide vs semaglutide weight loss superiority.

Related guide: Tirzepatide vs semaglutide weight loss comparison kg.

04 · SURMOUNT-5 in detail

SURMOUNT-5: what the head-to-head trial found

SURMOUNT-5 randomised 751 adults to tirzepatide or semaglutide 2.4mg (the Wegovy dose) for 72 weeks.¹⁵ Average weight loss was 20.2% on tirzepatide and 13.7% on semaglutide. In kilograms, that was 22.8 kg versus 15.0 kg.¹⁵

As a worked example, for someone starting at 100 kg, 20.2% is about 20 kg and 13.7% is about 14 kg. Your starting weight changes the kilogram figure, but the percentage is the fairer comparison between people.

These are trial averages. Individual results vary, and in the trials treatment is used alongside a reduced-calorie diet and increased physical activity, not instead of them.

05 · Loss thresholds compared

Who reached each weight loss threshold?

More people on tirzepatide reached every weight loss threshold measured in SURMOUNT-5. At least 10% of body weight was lost by 81.6% of people on tirzepatide versus 60.5% on semaglutide.¹⁵

The gap widens at higher thresholds:

• At least 15%: 64.6% on tirzepatide versus 40.1% on semaglutide.
• At least 20%: 48.4% versus 27.3%.
• At least 25%: 31.6% versus 16.1%.

Read this carefully. A majority of people on semaglutide still lost at least 10% of their body weight. The threshold figures show how often large losses occurred. They are not a promise of what you will lose, and they do not describe the many people whose result sat between the averages.¹⁵

06 · Why mechanisms differ

Why the two medicines work differently

Tirzepatide activates two natural gut-hormone receptors at once, GIP and GLP-1, while semaglutide is a single-action GLP-1 medicine.¹ Together these actions help regulate appetite, slow how quickly the stomach empties and improve the way the body responds to insulin. In practice, most people feel fuller sooner and less hungry between meals, which supports a reduced-calorie diet.

The dual action is what distinguishes Mounjaro from single-action medicines such as semaglutide. The trial measured outcomes, not the reasons for them.

07 · Other trial evidence

What the single-medicine trials add

Each medicine also has its own earlier trial, and these are useful context but not a head-to-head. In SURMOUNT-1, 2,539 adults on tirzepatide lost on average 15% of body weight on 5mg, 19.5% on 10mg and 20.9% on 15mg over 72 weeks, compared with 3.1% with lifestyle changes alone.²

In STEP 1, adults on semaglutide 2.4mg lost on average 14.9% of body weight over 68 weeks, compared with 2.4% on placebo.⁹ Of those, 86.4% lost at least 5%, 69.1% lost at least 10% and 50.5% lost at least 15%, against 31.5%, 12.0% and 4.9% on placebo.⁹

Those two sets of numbers come from different studies with different people and different lengths, so do not line them up against each other. Only SURMOUNT-5 supports a direct comparison.¹⁵ For dose-by-dose detail, see our page on dosage for weight loss.

08 · Side effects and hair loss

Side effects: is one gentler?

SURMOUNT-5 reported weight outcomes, so there is no head-to-head side-effect comparison for these two medicines. In STEP 1, gastrointestinal side effects were reported by 74.2% of people on semaglutide 2.4mg versus 47.9% on placebo, and 7.0% stopped treatment because of side effects versus 3.1% on placebo.⁹

If you notice hair thinning or any new symptom, tell your prescriber, and report suspected side effects through the Yellow Card scheme.¹⁹

09 · Switching and safety

Switching between semaglutide and tirzepatide

There is no licensed direct conversion between semaglutide and tirzepatide. Switching is done under prescriber supervision: typically the previous medicine is stopped, a washout interval is observed, and Mounjaro is started at a dose your prescriber judges appropriate. That is often the 2.5mg starting dose, sometimes adjusted based on your history. Never run two GLP-1 medicines together.

The same caution applies to unlicensed products. Mounjaro must not be combined with other GLP-1 medicines, unlicensed research peptides such as retatrutide (which has no UK licence) or compounded copies. These combinations have no safety data and no regulated supply chain. Anything promising faster results outside a licensed pathway is a warning sign.

If you take semaglutide as Ozempic, note that Ozempic is licensed for type 2 diabetes, not weight loss, so prescribing it privately for weight loss is off-label. The licensed weight-management options are Mounjaro and Wegovy.

10 · Tablets and NHS access

Tablets, and what about the NHS?

There is no tablet form of Mounjaro, because tirzepatide is injection-only in the UK. Two GLP-1 weight-loss tablets are now licensed: Wegovy tablets (oral semaglutide), approved by the MHRA in June 2026, and Foundayo (orforglipron), approved in August 2026.²⁰²¹ They are different medicines with their own dosing, eligibility checks and trial results, so do not read SURMOUNT-5 as covering them.

Mounjaro is available on the NHS, but access is being phased in over several years. NICE recommends it for adults with a BMI of at least 35 plus at least one weight-related condition, and the NHS primary-care rollout began in June 2025 with the highest-need groups first, initially BMI 40+ with four or more qualifying conditions.⁴ Full rollout is expected to take years, which is why many people who meet the licensed criteria choose regulated private treatment. NHS access to Wegovy runs through specialist weight-management services; ask your GP.

11 · Serious side effects

Serious side effects: when to get help straight away

Serious side effects are uncommon but need urgent attention. Seek immediate medical help for: severe, persistent stomach pain that may spread to your back, with or without vomiting (possible pancreatitis); pain in the upper right abdomen, fever or yellowing of skin/eyes (possible gallbladder problems); or signs of a severe allergic reaction such as swelling of the face or throat and difficulty breathing. If you take insulin or a sulfonylurea alongside Mounjaro, watch for low blood sugar (shakiness, sweating, confusion) — your prescriber may need to adjust those medicines.¹

12 · Ordering with us

How ordering works with EverydayMeds

We are a GPhC-registered UK online pharmacy (registration 9012878), and our Mounjaro comes direct from Eli Lilly's UK distribution through official LillyDirect supply. All six doses, 2.5mg to 15mg, are in stock. Ordering takes three steps:

• Free online consultation. A short health questionnaire, with no charge and no obligation.
• Prescriber review. A GPhC-registered prescriber reviews it. Payment is taken when you place the order; if the prescriber decides the treatment is not suitable, the order is refunded automatically in full.
• Dispatch and delivery. Same-day dispatch when ordered by 3pm, then free next-day tracked delivery in temperature-controlled packaging. Saturday delivery is £14.99.

Your first 2.5mg pen costs £129.99 with code FIRST40 (standard price £169.99). Every later order is £25 off the standard price (code DOSE25). Mounjaro is a prescription-only medicine, supplied only after an online consultation reviewed by a GPhC-registered prescriber, and used alongside a reduced-calorie diet and increased physical activity. Individual results vary. You can compare more options on our weight loss treatments page.