Difference Between Semaglutide vs Tirzepatide (October 2026)

01 · The verdict

Which suits whom: the short verdict

Tirzepatide produced larger average weight loss than semaglutide 2.4mg in the first large head-to-head trial, but both are effective, licensed treatments. Which suits you depends on your health profile, tolerance and prescriber advice, not the headline number alone.¹⁵

Tirzepatide and semaglutide are both licensed options, and your prescriber decides which suits you. Semaglutide (as Wegovy) may suit people whose prescriber prefers it for their history, or who have already done well on it. You can see the Mounjaro pen prices and consultation or the Wegovy pen.

02 · Side by side

Semaglutide vs tirzepatide comparison table

Only SURMOUNT-5 supports a direct comparison. Individual results vary.

03 · Deciding

Decision factors beyond weight loss

Your prescriber weighs medical history, previous response, tolerance and goals. Treatment works alongside a reduced-calorie diet and more physical activity, not instead of them.

If you want a deeper walk-through, see our guide to the difference between Wegovy and Mounjaro, or whether Wegovy is semaglutide vs Mounjaro. New customers save £40 on their first Mounjaro order with code FIRST40, and an automatic £25 reorder discount applies to every future order (code DOSE25).

Related guide: Whats the difference between semiglutide and tirzepatide.

Related guides: Difference between liraglutide semaglutide and tirzepatide and What is the main difference between semaglutide and tirzepatide.

04 · How each works

How they work differently

Tirzepatide is the first treatment of its kind to activate two natural gut-hormone receptors at once: GIP and GLP-1. Together these help regulate appetite, slow how quickly the stomach empties and improve the body's response to insulin.¹

Semaglutide is a single-action GLP-1 medicine. Most people on tirzepatide feel fuller sooner and less hungry between meals, which supports a reduced-calorie diet.¹

05 · Trial results in detail

Trial results in more detail

In SURMOUNT-5, 751 adults took tirzepatide or semaglutide 2.4mg for 72 weeks. At least 10% of body weight was lost by 81.6% on tirzepatide vs 60.5% on semaglutide; at least 15% by 64.6% vs 40.1%; at least 20% by 48.4% vs 27.3%; at least 25% by 31.6% vs 16.1%.¹⁵

In STEP 1, 86.4% on semaglutide 2.4mg lost at least 5% over 68 weeks (31.5% on placebo), 69.1% lost at least 10% and 50.5% lost at least 15%. Gastrointestinal side effects were reported by 74.2% on semaglutide versus 47.9% on placebo, and 7.0% stopped because of side effects (3.1% on placebo).⁹

For a worked example, someone starting at 100 kg who matched the 20.2% tirzepatide average would lose about 20 kg; trial averages do not predict your own result.

06 · Ozempic and licensing

Ozempic, Wegovy and Mounjaro licensing

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

07 · Switching and safety

Switching and what not to mix

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 observed, and Mounjaro started at a dose your prescriber judges appropriate, often the 2.5mg starting dose, sometimes adjusted based on your history. Never run two GLP-1 medicines together.¹

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 have no safety data and no regulated supply chain.⁷

08 · 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

09 · NHS and cheaper options

NHS access and alternatives

Mounjaro is available on the NHS, but access is 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 primary-care rollout began in June 2025 with the highest-need groups first (initially BMI 40+ with four or more qualifying conditions).⁴⁶

There is no tablet form of Mounjaro. Wegovy tablets and Foundayo are separate licensed tablets with their own dosing and trial results. "Natural GLP-1" supplements such as berberine are not medicines and have no comparable trial evidence. Browse all weight loss treatments.²⁰

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