Semaglutide or Tirzepatide: Which Is Better? (October 2026)

01 · The verdict

Which is better, tirzepatide or semaglutide?

In SURMOUNT-5, the first large head-to-head trial, average weight loss was higher on tirzepatide. In SURMOUNT-5, 751 adults took tirzepatide or semaglutide 2.4mg for 72 weeks. Average loss was 22.8 kg on tirzepatide versus 15.0 kg on semaglutide.¹⁵

That does not make semaglutide a poor choice. Both are effective, licensed treatments, and which suits you depends on your health profile, tolerance and prescriber advice, not the headline number alone.¹⁵ If you want to compare the two by brand, our guide to what's better, Mounjaro or semaglutide goes through the same evidence.

Tirzepatide may suit you if your prescriber agrees it is appropriate for your health profile. Semaglutide may suit you if your prescriber judges it a better fit for your history, or if you have already done well on it and tolerate it.

02 · Side by side

Tirzepatide vs semaglutide compared

Standard Mounjaro prices run from £169.99 (2.5mg) to £329.99 (15mg) for one 4-week pen. A new customer's first order is £40 less with code FIRST40, and every later order is £25 off the standard price (code DOSE25). You can see the Mounjaro pen prices and consultation and the Wegovy pen on their product pages.

03 · How to choose

Decision factors beyond the headline number

Four practical factors matter more than which trial number is larger. The first is your medical history, which only a prescriber can weigh. The second is tolerance: GI side effects are common with this class, and how you cope with them affects whether you can stay on treatment. The third is cost over a year. The fourth is how you respond once treatment starts.

On cost, if you step up after 4 weeks on each dose, your first four pens of Mounjaro (2.5mg to 10mg) cost £959.96 at standard prices. A first year costs £2,711.88 if you stay on 5mg after your 2.5mg starting pen, up to £3,599.88 if you step up through every dose to 15mg. Your first order is £40 less and every later order £25 less.

To see how the brands compare when the question is framed differently, read whether semaglutide or Mounjaro is better for weight loss, or the page on what is more effective, semaglutide or tirzepatide.

04 · What the trials show

What the trials actually show

Only SURMOUNT-5 compares the two medicines directly. In it, the share of people losing at least 10% of body weight was 81.6% on tirzepatide versus 60.5% on semaglutide 2.4mg. At least 15%: 64.6% versus 40.1%. At least 25%: 31.6% versus 16.1%.¹⁵

Each medicine also has its own placebo-controlled trial. In SURMOUNT-1 (2,539 adults), people on tirzepatide with diet and exercise 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% over 68 weeks, compared with 2.4% on placebo.⁹

Those two trials were separate studies, so their numbers should not be set side by side as a comparison. Use SURMOUNT-5 for that. For a worked example, someone starting at 100 kg who matched the SURMOUNT-1 15mg average of 20.9% would lose about 21 kg. These are trial averages, individual results vary, and both treatments work alongside a reduced-calorie diet and more physical activity, not instead of them.²

05 · Safety and drawbacks

Which is safer, and what are the drawbacks?

Both are prescription-only medicines licensed in the UK, and both are used under prescriber supervision. Our page on whether semaglutide or tirzepatide is safer covers this question in more depth.

For semaglutide 2.4mg, STEP 1 reported gastrointestinal side effects in 74.2% of people, compared with 47.9% on placebo. In that trial, 7.0% stopped treatment because of side effects, compared with 3.1% on placebo.⁹ The full list of known side effects for each medicine is in its patient information leaflet.¹³¹⁸

Common drawbacks of tirzepatide are practical ones: it is a weekly injection, it is a private cost for many people while NHS access is phased, and it only works alongside diet and activity. If you notice any new symptom, tell your prescriber and report it through the Yellow Card scheme.¹⁹

06 · Muscle, heart and gaps

Muscle loss and heart health

Some of any rapid weight loss comes from lean tissue. Adequate protein at every meal and resistance exercise two or more times a week help protect muscle.

If heart disease is part of your history, discuss it with your prescriber, who can weigh it when choosing between treatments.

See our page on semaglutide or tirzepatide for inflammation.

07 · Ozempic and other brands

Ozempic, Wegovy, tablets and other options

Ozempic is semaglutide licensed for type 2 diabetes. It is not a UK weight-loss medicine, and prescribing it privately for weight loss is off-label. The licensed weight-management options are Mounjaro (tirzepatide) and Wegovy (semaglutide 2.4mg), so "Mounjaro vs Ozempic" for weight loss is really Mounjaro vs Wegovy. A regulated UK pharmacy will not supply Ozempic for weight loss.¹⁸ More on this in which is better, Mounjaro or Ozempic and which has better results.

There is no tablet form of Mounjaro. Two GLP-1 weight-loss tablets are now licensed in the UK: Wegovy tablets (oral semaglutide), approved by the MHRA in June 2026, and Foundayo (orforglipron), approved in August 2026. They are different medicines with their own dosing, eligibility checks and trial results, and both are prescription-only.²⁰²¹

As for the "poor man's Ozempic", the label is usually applied to supplements such as berberine. These are low-cost supplements with no clinical oversight. They are not medicines, are not regulated for this use and have no comparable trial evidence.²⁰ Orlistat is a licensed tablet that blocks some dietary fat absorption and produces smaller average losses.

08 · Switching and never stacking

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, often the 2.5mg starting dose and sometimes adjusted based on your history.¹

Never run two GLP-1 medicines together. Mounjaro must also not be combined with 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 the warning sign.

If you are switching to us from another provider, the new-customer discount of £40 applies to your first order at any dose with code FIRST40. Switching at 15mg? Your first order is £289.99.

09 · NHS or private

NHS access versus private treatment

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. The NHS primary-care rollout began in June 2025 with the highest-need groups first (initially BMI 40+ with four or more qualifying conditions).⁴⁶ 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.

10 · 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

11 · How ordering works

How ordering works with us

Starting is free and carries no obligation. Our service is built around three steps:

• Free online consultation. A short health questionnaire, with no charge.
• 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.

Our Mounjaro comes from official LillyDirect supply, and all six doses are in stock. Start your free consultation or browse all weight loss treatments. Mounjaro (tirzepatide) is prescription-only, used alongside a reduced-calorie diet and increased physical activity, and individual results vary.