Which weight loss injection brands are licensed in the UK?

What separates the two brands, and why it matters for your decision

Most people searching for weight loss injection brands arrive at the same question: Mounjaro or Wegovy? The honest answer is that neither is universally "better", they work through related but distinct pathways, carry broadly similar side-effect profiles, and suit different people for different clinical reasons.

Mounjaro is a dual GIP and GLP-1 receptor agonist, the only medicine of its kind licensed for weight management in the UK. It activates two gut-hormone receptors at once, which researchers believe contributes to its results in trials. Wegovy is a GLP-1 receptor agonist (the same class as several older diabetes medicines) and was the first injection of this type to receive a dedicated UK weight-management licence. Both slow gastric emptying, reduce appetite, and work best alongside changes to diet and activity. The full picture of how weight loss injections work is worth reading if you want the mechanism explained in plain terms.

Clinically, the distinction isn't just academic. The SURMOUNT-5 trial, published in the New England Journal of Medicine in 2025, compared tirzepatide directly against semaglutide 2.4mg in adults with obesity and found tirzepatide produced greater average weight loss over 72 weeks. The gap is real, though narrowing: the MHRA approved a dedicated single-dose 7.2mg Wegovy pen in April 2026, and at that higher dose, semaglutide's results move closer to tirzepatide's top dose. That said, the prescriber's job is to match the medicine to the patient, not to chase the highest trial average.

Which brand might a prescriber lean towards, and on what grounds?

A prescriber considers several things before recommending one brand over the other. Eligibility is the first filter: both are licensed for adults with a BMI of 30 or above, or 27 or above alongside a weight-related condition such as high blood pressure, high cholesterol, obstructive sleep apnoea, or type 2 diabetes. Lower thresholds apply for some ethnic backgrounds under UK guidance.

Beyond the licence, they'll look at your full medical history. Anyone taking oral contraceptives starting Mounjaro is advised to use an additional non-oral method of contraception for the first four weeks of treatment and for four weeks after each dose increase, because tirzepatide can slow the absorption of the pill. Semaglutide doesn't carry the same evidence-based flag. This is exactly the kind of detail that shapes a real clinical decision, not just "which one works better on average".

If you've already been on one brand and it didn't suit you, that's also relevant information. Patients transferring from another provider should expect a prescriber to ask for evidence of their current treatment before continuing. You can read more about the name-brand medicines available and what transferring means in practice.

Some people ask specifically about off-brand or unlicensed alternatives, it's worth understanding why those carry different risks before going down that route.

What the NHS and NICE say about each brand

The two brands sit in slightly different positions in NHS guidance. NICE recommended tirzepatide (Mounjaro) in December 2024 under appraisal TA1026, for adults with a BMI of 35 or above plus at least one weight-related comorbidity; the NHS is rolling out access in phased cohorts through 2025 and 2026. NICE recommended semaglutide (Wegovy) earlier, under TA875, but with tighter conditions: it's approved for use within specialist weight management services only, for a maximum of two years.

In practice, NHS access for both brands involves waiting lists and strict criteria. Many people find that understanding where to obtain these injections legally and safely is the more pressing question, especially when NHS eligibility is months or years away. A private prescription through a registered online pharmacy is a legitimate route, provided the pharmacy is on the GPhC register and every prescription is issued by a qualified prescriber after a proper assessment.

If you're based in a specific region and wondering about local availability, the picture varies: you can find more detail about access to weight loss injections in the West Midlands as one example of how regional rollout works.

Payday timing, holidays, and the day of the week all affect when orders actually land. A Monday order placed before 12pm, once approved, ships the same day and arrives Tuesday. Worth factoring in around bank holidays if you're planning ahead.

Side effects, safety, and what to watch for

The side-effect profiles of Mounjaro and Wegovy overlap significantly. Both commonly cause nausea, vomiting, diarrhoea, constipation, reflux, and fatigue, particularly in the first few weeks of starting or after a dose increase. These effects settle for most people as the body adjusts. Neither brand is recommended during pregnancy, whilst breastfeeding, or when trying to conceive; use in under-18s is outside the licensed indication.

Pancreatitis is a known but infrequent risk with GLP-1 medicines generally. The MHRA highlighted this in a Drug Safety Update in January 2026: severe, persistent stomach pain that radiates to the back, with or without vomiting, is a reason to seek urgent medical attention. Any suspected side effect from either brand can be reported to the MHRA via the Yellow Card scheme.

For a fuller look at the broader weight loss treatment landscape, including what lifestyle changes work alongside either brand, that overview is a useful starting point. And if you're interested in the specifics of what a name-brand injection course actually involves day to day, the step-by-step guide to weight loss injections covers that in plain terms.

Choosing between these brands is a clinical conversation, not a consumer one. If you'd like to start that conversation with a real prescriber, you can begin your free consultation with our clinical team, no referral, no waiting list, reviewed the same day.