Should I Get Semaglutide or Tirzepatide? (October 2026)

01 · The short verdict

Which one suits you?

Which medicine suits you depends on your health profile, tolerance and prescriber advice; the prescriber decides, and neither is right for everyone. In SURMOUNT-5, 751 adults took either medicine for 72 weeks, and average loss was 22.8 kg on tirzepatide versus 15.0 kg on semaglutide.¹⁵

Which suits you depends on your health profile, tolerance and prescriber advice, not the headline number alone.¹⁵ For a deeper side-by-side, see which is better semaglutide or tirzepatide and what's better Mounjaro or semaglutide.

You can view the Mounjaro pen and the Wegovy pen prices and options on their product pages.

02 · Cost

What does each cost?

Mounjaro pens are £169.99 at 2.5mg and £218.99 at 5mg per month, rising to £329.99 at 15mg. New customers save £40 on their first order with code FIRST40, and an automatic £25 reorder discount applies to every future order (code DOSE25). If you step up after 4 weeks on each dose, your first four pens (2.5mg to 10mg) cost £959.96 at standard prices.

Your first 2.5mg Mounjaro pen costs £129.99 with code FIRST40, and your first Wegovy pen is £99.99 — both are first-order prices.

03 · How ordering works

How to get either medicine

First, complete a free online consultation, a short health questionnaire with no obligation. Second, a GPhC-registered prescriber reviews your consultation. Payment is taken when you place the order; if the prescriber decides the treatment is not suitable, the order is refunded automatically in full. Third, our registered pharmacy dispenses and dispatches, with same-day dispatch when ordered by 3pm and free next-day tracked delivery. Mounjaro is supplied via official LillyDirect supply, and all six doses are in stock. You can also buy Mounjaro directly.

04 · How they differ

How tirzepatide and semaglutide differ

Tirzepatide activates two natural gut-hormone receptors, GIP and GLP-1, which together 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.¹

Mounjaro is a once-weekly pre-filled KwikPen in six strengths: 2.5mg, 5mg, 7.5mg, 10mg, 12.5mg and 15mg.¹ Wegovy comes in 0.25mg, 0.5mg, 1mg, 1.7mg and 2.4mg pens, stepping up after at least four weeks to the 2.4mg maintenance dose from week 17.¹⁸

05 · Trial results

What the trials show

In SURMOUNT-5, at least 10% of body weight was lost by 81.6% on tirzepatide versus 60.5% on semaglutide; at least 15% by 64.6% versus 40.1%; and at least 25% by 31.6% versus 16.1%.¹⁵

In SURMOUNT-1 (2,539 adults), tirzepatide averaged 15% weight loss on 5mg, 19.5% on 10mg and 20.9% on 15mg over 72 weeks, versus 3.1% with lifestyle changes alone.² In STEP 1, semaglutide 2.4mg averaged 14.9% over 68 weeks versus 2.4% on placebo.⁹ These are separate trials and should not be set side by side; trial averages do not predict your own result, and treatment works alongside a reduced-calorie diet and more activity.

06 · Side effect profiles

Side effect profiles

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%.⁹

Common side effects of Mounjaro, affecting more than 1 in 10 people, are nausea, diarrhoea, vomiting, constipation and abdominal discomfort. Side effects are most likely when starting treatment or moving up a dose, and for most people they ease within days to a few weeks. Your prescriber will discuss tolerance with you. Report any side effect through the Yellow Card scheme.¹⁹ For more, see is semaglutide or tirzepatide safer.

07 · Eligibility and NHS

Eligibility and NHS access

Mounjaro is licensed for weight management in adults with a BMI of 30 or above, or 27 to 30 with at least one weight-related condition such as high blood pressure, high cholesterol, obstructive sleep apnoea, cardiovascular disease, prediabetes or type 2 diabetes. It must be used with a reduced-calorie diet and more physical activity, and a prescriber assesses your BMI, history and current medicines.¹

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 a weight-related condition, and the primary-care rollout began in June 2025 with the highest-need groups first.⁴

08 · Ozempic, switching, safety

Ozempic, switching and stacking

Ozempic is semaglutide licensed for type 2 diabetes, not weight loss, so prescribing it for weight loss is off-label. The licensed weight options are Mounjaro and Wegovy.¹⁸ See is Ozempic a semaglutide or tirzepatide.

There is no licensed direct conversion between the two. Switching is supervised: the previous medicine is stopped, a washout interval observed, and Mounjaro 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 If you use the contraceptive pill, Mounjaro slows stomach emptying, which can reduce how well it is absorbed: switch to a non-oral method, or add a barrier method (such as condoms), for 4 weeks after starting Mounjaro and for 4 weeks after each dose increase.

Mounjaro is prescription-only, supplied after a consultation reviewed by a GPhC-registered prescriber. Information here is not a substitute for medical advice.

09 · 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