GLP-1 Comparison UK: Mounjaro, Wegovy, Ozempic and Tablets (October 2026)

01 · The verdict

Which GLP-1 suits whom: the short verdict

For licensed weight management by injection, the real choice is Mounjaro or Wegovy. In SURMOUNT-5, 751 adults took tirzepatide or semaglutide 2.4mg for 72 weeks. Average loss was 22.8 kg on tirzepatide and 15.0 kg on semaglutide.¹⁵ Which suits you depends on your health profile, tolerance and prescriber advice, not the headline number alone.¹⁵

Mounjaro and Wegovy are both effective, licensed treatments, and your prescriber decides which suits you. Ozempic is the wrong comparison for weight loss: it is licensed for type 2 diabetes, and a regulated UK pharmacy will not supply it for weight loss.¹⁸

02 · Side by side

GLP-1 medicines compared

Read the trial column carefully. SURMOUNT-5 is the first large head-to-head trial, comparing tirzepatide directly with semaglutide 2.4mg in the same study. SURMOUNT-1 and STEP 1 were separate trials with different populations and durations, so their numbers should not be set against each other. Trial averages do not predict your own result, and treatment works alongside a reduced-calorie diet and increased physical activity.²

03 · Deciding

The decision factors that matter in practice

Start with licensing. A medicine used for weight loss should be licensed for it, supplied after a consultation reviewed by a GPhC-registered prescriber, and dispensed by a registered pharmacy. Mounjaro and Wegovy meet that bar; supplements and unlicensed peptides do not.

Next, consider dosing convenience. Mounjaro and Wegovy are once-weekly pens, while liraglutide is a daily injection. Then consider cost. Across the UK pharmacies we track, the cheapest and dearest Mounjaro pen at any dose ranges from £143.96 to £339.00 per month (checked 10 October 2026). You can see the current Mounjaro pen prices and consultation or the Wegovy pen prices.

Finally, think about your own health. Other medicines you take, previous reactions to semaglutide and your health conditions all shape which option a prescriber will recommend. The consultation is free, and you can start your free consultation to have that review.

04 · How GLP-1s work

How GLP-1 medicines work, and what makes tirzepatide different

GLP-1 medicines act on natural gut-hormone receptors that help regulate appetite and how the body handles food. Mounjaro (tirzepatide) is the first treatment of its kind to activate two of these receptors at once: GIP and GLP-1.¹ Semaglutide, in Wegovy and Ozempic, is a single-action GLP-1 medicine. That dual action is what distinguishes Mounjaro from single-action GLP-1 medicines.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.¹ The medicine does not replace the diet; it makes it easier to follow.

This is why the term 'GLP-1' is slightly loose. People use it for the whole family, including tirzepatide, even though tirzepatide also acts on GIP.

Mounjaro in brief

Mounjaro is the brand name for tirzepatide, a once-weekly injectable prescription medicine made by Eli Lilly. In the UK it is licensed for weight management in adults and for type 2 diabetes. It comes as a pre-filled multi-dose pen (KwikPen) in six strengths: 2.5mg, 5mg, 7.5mg, 10mg, 12.5mg and 15mg.¹

How long it stays in the body

Tirzepatide has a half-life of about five days. After a final dose it takes roughly 4 to 5 weeks to clear the system. There is no way to speed this up, and nothing needs doing while it clears.¹ That matters when you compare medicines or plan a switch, because effects and side effects do not stop the day you stop injecting.

Why slower stomach emptying matters

Slower stomach emptying is part of why you feel full sooner. It also means some oral medicines may be absorbed differently, particularly when you start treatment or increase the dose.¹³

For a deeper look at the class, see our guide to how individual GLP-1 agonists differ.

05 · What the trials show

What the main trials show for tirzepatide and semaglutide

Three trials carry most of the weight in this comparison: SURMOUNT-1 for tirzepatide, STEP 1 for semaglutide 2.4mg, and SURMOUNT-5 for the two head to head. Each should be read on its own terms.

SURMOUNT-1: tirzepatide against lifestyle alone

In SURMOUNT-1, 2,539 adults taking tirzepatide alongside diet and exercise lost on average 15% of their body weight on 5mg, 19.5% on 10mg and 20.9% on 15mg over 72 weeks. Lifestyle changes alone produced 3.1%.² At 72 weeks, 85% of participants on 5mg, 89% on 10mg and 91% on 15mg had lost at least 5% of their body weight. Half of those on 10mg and 57% on 15mg lost at least 20%.² These are trial averages, and individual results vary.

As a worked example, for someone starting at 100 kg, 20.9% is about 21 kg. That is straight arithmetic from the trial average, not a promise for any individual.

STEP 1: semaglutide 2.4mg against placebo

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

SURMOUNT-5: the head-to-head

SURMOUNT-5 is the first large head-to-head trial of tirzepatide and semaglutide for weight loss. Over 72 weeks, adults on tirzepatide lost on average 20.2% of body weight versus 13.7% on semaglutide 2.4mg.¹⁵ The threshold breakdown shows the same direction:

Average loss was 22.8 kg on tirzepatide against 15.0 kg on semaglutide.¹⁵

Reading the numbers sensibly

Averages hide a wide spread. Some people lose far more than the mean and some far less. Both medicines are effective, licensed treatments, and the better choice for you also depends on tolerance and prescriber advice. For more charts, see our weight-loss comparison chart.

06 · Licensed or not

Which GLP-1 options are licensed for weight loss in the UK

The licensed injectable options are Mounjaro (tirzepatide) and Wegovy (semaglutide 2.4mg). Saxenda (liraglutide) is another licensed injectable.¹¹⁸

Ozempic

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. So 'Mounjaro vs Ozempic' for weight loss is really Mounjaro vs Wegovy, and a regulated UK pharmacy will not supply Ozempic for weight loss.¹⁸ If you want the head-to-head evidence, it is the SURMOUNT-5 data.

Liraglutide (Saxenda)

Liraglutide is supplied at 6mg per millilitre and is a daily injection, unlike once-weekly Mounjaro and Wegovy.

The new tablets

There is no tablet form of Mounjaro. Tirzepatide is injection-only in the UK. Two GLP-1 weight-loss tablets are now licensed: Wegovy tablets (oral semaglutide, made by Novo Nordisk), approved by the MHRA in June 2026, and Foundayo (orforglipron, made by Eli Lilly), approved in August 2026.²⁰²¹ They are different medicines from Mounjaro, with their own dosing, eligibility checks and trial results, and both are prescription-only.

Orlistat and supplements

Orlistat is a tablet that blocks some dietary fat absorption and produces smaller average losses. 'Natural GLP-1' supplements, such as berberine, are not medicines, are not regulated for this use and have no comparable trial evidence.¹ Dosing is not standardised, and they are available cheaply without assessment. That cheapness is a reason for caution, not a recommendation. Phrases like 'poor man's Ozempic' or 'the closest natural thing' describe marketing, not an equivalent treatment.

Unlicensed 'research' peptides

Retatrutide has no UK licence. Products sold as research peptides or compounded copies carry no safety data and no regulated supply chain. If something promises faster results outside a licensed pathway, that is the warning sign.

07 · Dosing and storage

Dosing, titration and storage compared

Both Mounjaro and Wegovy are started low and increased in steps, but the ladders differ. Mounjaro pens come in six strengths: 2.5mg, 5mg, 7.5mg, 10mg, 12.5mg and 15mg.¹ Your prescriber decides the pace, based on how you tolerate each step and your response.

Wegovy's ladder runs 0.25mg, 0.5mg, 1mg, 1.7mg and 2.4mg once weekly. It steps up after at least four weeks and reaches the 2.4mg maintenance dose from week 17. The 2.4mg dose is the licensed maintenance dose for weight management.¹⁸

Storing a Mounjaro pen

Unopened pens are stored in the fridge until first use, and they keep until the printed expiry date. Once in use, a pen can be kept out of the fridge at a temperature not above 30°C for up to 30 days after first use, and must then be thrown away. If you are unsure about an unopened pen that has been out of the fridge, check the patient information leaflet and ask the pharmacy rather than guessing.¹³

Why you should not adjust doses yourself

Each pen is designed for a defined schedule, and a prescriber sets any change. If you miss a dose, take it as soon as you can within 4 days (96 hours) of the scheduled time. If more than 4 days have passed, skip the missed dose and take the next one on your normal day. Never take two doses within 3 days of each other.

Treatment length

Weight loss in the trials happened over 68 to 72 weeks, and treatment is used alongside a reduced-calorie diet and increased physical activity. Your prescriber reviews progress and tolerance at each stage, which is why ongoing monthly reviews form part of our service.

For a fuller side-by-side of the class, see our overview of GLP-1 drugs.

08 · Cost over a year

What GLP-1 treatment costs over a year

Cost depends on the medicine, the dose you settle at and how long you stay on treatment.

If you step up after 4 weeks on each dose, your first four pens (2.5mg to 10mg) cost £959.96 at standard prices. A first year (13 pens) 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. A new customer's first order is £40 less, and every later order is £25 less.

Your first 2.5mg pen costs £129.99 with code FIRST40. Switching to us at 15mg? Your first order is £289.99. After that, an automatic £25 reorder discount applies to every future order (code DOSE25), taken off the standard price of that dose.

How the wider market looks

Across the UK pharmacies we track, the cheapest starting 2.5mg pen is £143.96 and the dearest is £179.99 (checked 10 October 2026). For the same dose, the gap between providers ranges from £27 to £41. Boots' Mounjaro dose prices run from £179.00 to £339.00.

Wegovy cost

A first Wegovy pen starts at £99.99 on a first order. Compare more in our cost comparison of GLP-1 drugs.

Planning rather than chasing the lowest number

A low starting price matters less than the total across the dose you will really use. Ask what each provider charges at 5mg, 10mg and 15mg, whether consultations are free, and whether delivery is included. Our consultation is free, the price shown is the price paid, and delivery is free next-day tracked. You can pay with Visa or Mastercard, Klarna or pay-monthly options, and there is no subscription.

09 · NHS and safety

NHS access, side effects and the downsides to weigh up

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 rather than waiting. NHS access to Wegovy runs through specialist weight-management services; ask your GP.

Downsides to know before starting

Every GLP-1 medicine has downsides, and stomach-related effects are the best documented. In STEP 1, gastrointestinal side effects were reported by 74.2% of people on semaglutide 2.4mg, compared with 47.9% on placebo. 7.0% stopped treatment because of side effects, against 3.1% on placebo.⁹ The most common Mounjaro side effects, 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.¹³ If you notice a new symptom, tell your prescriber and report it through the Yellow Card scheme.¹⁹

Interactions and contraception

Because Mounjaro slows stomach emptying, it can affect how quickly some oral medicines are absorbed, particularly when you start treatment or increase the dose. Tell your prescriber about everything you take, especially warfarin or other narrow-margin medicines, insulin, or sulfonylureas, where doses may need reducing to avoid low blood sugar. No adjustment is needed for paracetamol.¹³ Mounjaro slows stomach emptying, which can reduce how well oral contraceptive pills are absorbed.⁷ The SmPC advises switching to a non-oral method, or adding a barrier method (such as condoms), for 4 weeks after starting Mounjaro and for 4 weeks after each dose increase.¹

10 · Switching and stacking

Switching between GLP-1 medicines, and why stacking is unsafe

There is no licensed direct conversion between semaglutide and tirzepatide, so any switch is a prescriber decision. 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.¹¹⁸

Why people consider switching

Typical reasons include a plateau, tolerability, or the head-to-head evidence in SURMOUNT-5. Others want to move from an off-label supply to a licensed weight-management medicine. Whatever the reason, discuss it with a prescriber rather than changing yourself.

Never run two GLP-1 medicines together

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.¹ If something promises faster results outside a licensed pathway, that is the warning sign.

Spotting counterfeit or unregulated supply

Check that a seller is a registered pharmacy. You can verify ours on the GPhC register, number 9012878.¹² Be wary of anyone offering to supply without a consultation or prescription, or advertising dramatic weight-loss claims. The MHRA publishes counterfeit medicine alerts and runs the Yellow Card scheme for reporting problems.⁷ Our Mounjaro comes from official LillyDirect supply, sourced directly from Eli Lilly's UK distribution, and every pen is a genuine KwikPen.

How ordering works

1. Complete a free online consultation: a short health questionnaire, no charge and no obligation. 2. Payment is taken when you place the order; if the prescriber decides the treatment is not suitable, the order is refunded automatically in full. 3. Our registered pharmacy dispenses your order, with same-day dispatch when ordered by 3pm, then free next-day tracked delivery in discreet, temperature-controlled packaging. Saturday delivery is £14.99. Needles, a sharps bin and injection guidance come with every order, and repeat orders re-check suitability with no auto-shipping.

Our full range is on the weight loss treatments hub, and our injection price comparison shows provider differences. in stock applies to all six doses at the time of order.

Mounjaro (tirzepatide) is a prescription-only medicine, supplied only after an online consultation reviewed by a GPhC-registered prescriber. It is used alongside a reduced-calorie diet and increased physical activity. Individual results vary. This page is information, not a substitute for medical advice.

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