Benefits of Tirzepatide vs Semaglutide (October 2026)

01 · The verdict

Which has the bigger benefits?

Tirzepatide has the larger average weight-loss benefit in the first large head-to-head trial, SURMOUNT-5. Semaglutide 2.4mg (Wegovy) remains an effective, licensed choice, and the better option depends on your health profile, tolerance and prescriber advice, not the headline number alone.¹⁵

Tirzepatide may suit people whose prescriber considers the greater average effect shown in SURMOUNT-5 appropriate for them. Semaglutide may suit people whose prescriber prefers its profile or who already tolerate it well. You can compare the Mounjaro pen and the Wegovy pen on their product pages, and our full tirzepatide vs semaglutide guide goes further.

02 · Side by side

Tirzepatide vs semaglutide: comparison

Only SURMOUNT-5 supports a direct comparison. SURMOUNT-1 and STEP 1 were separate trials and should not be set against each other. All figures are trial averages, and individual results vary.²⁹

03 · Deciding

Decision factors beyond weight loss

Tolerance, cost and licensing matter as much as the average. For a wider view, see our cost comparison and the weight loss superiority breakdown.

04 · How they work

How the two medicines 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 way the body responds to insulin. Most people feel fuller sooner and less hungry between meals, which supports a reduced-calorie diet.¹

This dual action distinguishes Mounjaro from single-action GLP-1 medicines such as semaglutide. Our mechanism of action comparison explains this in more detail.

05 · Side effects compared

Side effects and tolerability

Mounjaro's most common side effects, affecting more than 1 in 10 people, are nausea, diarrhoea, vomiting, constipation and abdominal discomfort. They are most likely when starting treatment or moving up a dose, and for most people ease within days to a few weeks.¹

In the weight-management trials, nausea was reported by 24.6% on 5mg, 29.0% on 10mg and 28.0% on 15mg, versus 8.5% on placebo. Diarrhoea affected 18.7%, 20.8% and 22.5% respectively, versus 7.8% on placebo.¹ In SURMOUNT-1, 4.3% on 5mg, 7.1% on 10mg and 6.2% on 15mg stopped because of side effects, versus 2.6% on placebo.²

In STEP 1, gastrointestinal side effects were reported by 74.2% of people on semaglutide 2.4mg, compared with 47.9% on placebo, and 7.0% stopped treatment because of side effects, compared with 3.1% on placebo. Separate trials should not be set against each other. Your prescriber can discuss what suits you, and our side effects comparison covers more. Get medical help straight away for severe, persistent stomach pain spreading to your back (possible pancreatitis), upper right abdominal pain with fever or yellowing of the skin or eyes (possible gallbladder problems), or signs of a severe allergic reaction.¹

06 · Muscle, face and hair

Muscle, face and hair changes

"Ozempic face" is not a drug effect. It is what losing a lot of weight quickly can do to facial volume, on any method including diet or surgery, and the same applies to loose skin. Adequate protein, resistance exercise and a loss pace guided by your prescriber help protect lean mass.

Hair loss was reported by 4.9% of people on tirzepatide in the weight-management trials, versus 1.0% on placebo, and is linked to rapid weight loss itself. See hair loss on both medicines.¹

07 · Mood and mental health

Mood, anxiety and depression

Neither medicine is licensed to treat anxiety or depression. Regulators have examined whether GLP-1 medicines are linked to low mood or suicidal thoughts: the EMA's safety committee concluded in 2024 that the evidence does not support a causal link, and the MHRA keeps this under continuous review.¹⁷

If you have thoughts of harming yourself or ending your life, get help straight away. Call 999 or go to A&E if you are in immediate danger. In England you can call NHS 111 and choose the mental health option, any time. You can also call Samaritans free on 116 123, day or night. Tell your prescriber about any change in your mood while taking Mounjaro.

Big changes in weight, appetite and routine can still affect how you feel. Tell your prescriber about any history of depression, and seek help promptly if your mood drops or you have distressing thoughts during treatment. Report suspected side effects through the Yellow Card scheme.¹⁹

08 · Switching and safety

Switching between them safely

There is no licensed direct conversion between semaglutide and tirzepatide. Switching happens under prescriber supervision: the previous medicine is stopped, a washout interval is observed, and Mounjaro is started at a dose your prescriber judges appropriate, often 2.5mg. Never run two GLP-1 medicines together, and avoid unlicensed "research" peptides or compounded copies, which have no safety data.¹

Ozempic is semaglutide licensed for type 2 diabetes, not weight loss, so for weight loss the real comparison is Mounjaro vs Wegovy. See Wegovy vs Mounjaro, or the diabetes comparison. Prefer tablets? Read Foundayo vs the semaglutide pill.

09 · Getting treatment

Getting Mounjaro from us

Mounjaro is available on the NHS, but access is being phased in over several years. The primary-care rollout began in June 2025 with the highest-need groups first, which is why many people choose regulated private treatment.⁴

Our process: a free online consultation, review by a GPhC-registered prescriber, dispensing with same-day dispatch when ordered by 3pm, then free next-day tracked delivery. Start your free consultation or see all weight loss treatments.

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