Best Weight Loss Injections in the UK: Which Is Right for You? (November 2026)

01 · The verdict

Which weight loss injection is best?

No licensed medicine is best for everyone, but the evidence gives a clear starting point. Mounjaro produced more weight loss on average than Wegovy in the only large head-to-head trial so far.⁵ Wegovy is still very effective, it is cheaper at the starting doses, and it now comes as a daily tablet for people who prefer not to inject.

• Most weight loss on average: Mounjaro.
• Lower starting cost: Wegovy.
• Prefer a tablet: Wegovy tablets or Foundayo.
• Tried one and stalled: switching to the other is common, and your prescriber can plan it.

In the free consultation you can say which treatment you are interested in, and a GPhC-registered prescriber reviews your answers and recommends what is suitable for you.

02 · Get started

How to get started

Choose Mounjaro or Wegovy, complete the free consultation, and if the prescriber approves it our pharmacy sends your pen with free next-day tracked delivery. New customers get £40 off the first order with code FIRST40, repeat orders are £25 off, and Subscribe & Save takes £40 off every order on injections.

Mounjaro and Wegovy are prescription-only medicines, supplied only after an online consultation reviewed by a GPhC-registered prescriber. They are used alongside a reduced-calorie diet and more physical activity. Individual results vary. This page is information, not a substitute for medical advice.

03 · The options in the UK

What weight loss injections are available in the UK?

Three injectable medicines are licensed for weight management in the UK:

• Mounjaro (tirzepatide), a once-weekly injection made by Eli Lilly. It acts on two gut-hormone receptors, GIP and GLP-1.¹
• Wegovy (semaglutide), a once-weekly injection made by Novo Nordisk. It acts on the GLP-1 receptor.²
• Liraglutide, sold as Saxenda and in other products, an older injection taken every day rather than every week.

All of them copy hormones that tell your brain you are full and slow the rate at which your stomach empties, so you feel satisfied with less food. They are used alongside a reduced-calorie diet and more physical activity, not instead of them.

You may also see Ozempic mentioned. It contains the same medicine as Wegovy but is licensed for type 2 diabetes, not weight management. Our page on Mounjaro vs Ozempic explains the difference.

04 · Results compared

How much weight do people lose on each injection?

Trial results give a fair comparison, because everyone in a trial follows the same diet and activity advice:

• In the SURMOUNT-1 trial of 2,539 adults, people 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, compared with 3.1% with lifestyle changes alone.³
• In STEP 1, adults on semaglutide 2.4mg lost on average 14.9% of body weight over 68 weeks, compared with 2.4% on placebo.⁴
• In SURMOUNT-5, which compared them directly, adults on tirzepatide lost on average 20.2% of body weight over 72 weeks versus 13.7% on semaglutide 2.4mg.⁵

These are averages. Some people lose much more and some much less on either medicine, and results depend on diet, activity, sleep and how long you stay on treatment. Both are effective, licensed treatments; which suits you depends on your health profile, tolerance and prescriber advice, not the headline number alone.

05 · Side effects compared

Weight loss injection side effects compared

The side effects of Mounjaro and Wegovy are very similar. The most common side effects are digestive: nausea, constipation, diarrhoea, vomiting, indigestion and stomach pain.¹² They are most likely in the first weeks and after each dose increase, and usually ease as your body adjusts. In STEP 1, gastrointestinal side effects were reported by 74.2% of people on semaglutide 2.4mg, compared with 47.9% on placebo.⁴

Serious side effects are uncommon but important. Seek immediate medical help for severe, persistent stomach pain that may spread to your back (possible pancreatitis), pain in the upper right abdomen with fever or yellowing of the skin or eyes (possible gallbladder problems), or signs of a severe allergic reaction.⁶ Our guide to Mounjaro side effects covers how to manage the common ones.

06 · Cost compared

How much do weight loss injections cost?

Each injection pen holds four weekly doses, so the pen price is your monthly cost. With us:

• Mounjaro: £169.99 for the 2.5mg pen up to £299.99 for 15mg, at standard prices. See all doses on our Mounjaro prices page.
• Wegovy: from £99.99 per pen. See our Wegovy prices page.

Across the UK pharmacies we track, Mounjaro pens range from £143.96 to £339.00, checked on 11 November 2026. The dose, and so the price, usually rises in the first few months, so compare what several months will cost rather than just the first pen. Our weight loss injections cost guide sets this out month by month.

07 · Which suits whom

Which injection suits which person?

Your prescriber weighs your health, other medicines and preferences. In broad terms:

Mounjaro may suit you if

• you want the largest average weight loss seen in trials;
• you have used semaglutide before and stopped losing weight;
• you are comfortable with a weekly injection.

Wegovy may suit you if

• lower cost matters most at the start;
• you have tolerated semaglutide well before;
• you would like the option of moving to a tablet later.

Either may not suit you if

you are pregnant or breastfeeding, or have a history of pancreatitis, gallbladder problems or severe digestive disease, in which case your prescriber will take extra care or may recommend against treatment.¹ Both are licensed for adults with a BMI of 30 or above, or 27 to under 30 with at least one weight-related condition.¹² Our full Mounjaro vs Wegovy comparison goes deeper.

08 · Injections or tablets

Weight loss injections or tablets?

Two GLP-1 weight-loss tablets are now licensed in the UK: 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 2026.⁷⁸

Tablets avoid injections but are taken every day and give smaller average weight loss than the strongest injections. In the OASIS 4 trial, adults taking semaglutide 25mg tablets for 64 weeks lost on average 13.6% of their body weight, compared with 2.2% on placebo.⁹ In the ATTAIN-1 trial, people taking the highest dose of orforglipron for 72 weeks lost on average 12.4% of their body weight, compared with 0.9% on placebo.¹⁰ Our guide to the best weight loss pills in the UK compares all the tablet options.

09 · How doses work

How the doses work

Both injections start low and increase gradually to reduce side effects. For Mounjaro, everyone starts on 2.5mg; after at least 4 weeks the dose rises to 5mg, then can step up by 2.5mg at intervals of at least 4 weeks, to a maximum of 15mg weekly.¹ For Wegovy, the dose steps up after 4 weeks on each of 0.25mg, 0.5mg, 1mg and 1.7mg, so the 2.4mg maintenance dose starts from week 17.²

You do not have to reach the highest dose. The right dose is the lowest one that keeps working for you with side effects you can live with, and your prescriber decides when to step up. Our Mounjaro dose schedule shows every step.

10 · NHS or private

Getting weight loss injections on the NHS or privately

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, and the NHS primary-care rollout began in June 2025 with the highest-need groups first.¹¹¹² Wegovy is also available on the NHS for people who meet the NICE criteria, mainly through specialist weight management services.

Privately, the licensed criteria are wider, and most people get their injections from a registered online pharmacy after a consultation. Whichever route you choose, only buy from a pharmacy you can find on the GPhC register.¹³ The MHRA has seized thousands of fake weight-loss pens in the UK.¹⁴

11 · Staying on treatment

Thinking long term

Weight tends to come back after stopping either injection. In SURMOUNT-4, people who stopped tirzepatide after 36 weeks regained on average 14% of body weight over the following year, while those who continued treatment lost a further 5.5% on average.¹⁵

So the best injection is also the one you can stay on: one you tolerate, can afford over a year or more and fits your routine. Many people start on one and switch later because of side effects, cost or a plateau. If that happens, the prescriber decides when to switch and which dose to start on.