The UK weight loss injections names list: what's licensed, what's not, and how they differ

Which names appear on the UK licensed list, and which don't belong there?

The shortest answer: Mounjaro and Wegovy. Those are the two brand names you'll find on the current UK licensed list for weight management in adults. Mounjaro contains tirzepatide, made by Eli Lilly. Wegovy contains semaglutide 2.4 mg (now up to 7.2 mg following MHRA approval of a dedicated single-dose pen in April 2026), made by Novo Nordisk. Both require a prescription following clinical assessment, and both carry the Black Triangle symbol, meaning the MHRA actively collects additional safety data on them.

Then there are names that cause genuine confusion. Ozempic is semaglutide, the same active ingredient as Wegovy, but its UK licence covers type 2 diabetes management, not weight loss. Prescribing it for weight management would be off-label, which is a clinical decision requiring specific justification. Saxenda (liraglutide) holds a UK weight-management licence but is not currently dispensed at nume, sorry, at nume. And Zepbound is the US brand name for tirzepatide; it does not exist as a UK product. If you've read about it online, the UK equivalent is Mounjaro. Our list of all weight loss injections available in the UK covers each option in more detail, including both licensed and unlicensed names you're likely to encounter.

Worth knowing: the NHS notes clearly that GLP-1 medicines are not assessed or approved for cosmetic weight loss, they're prescribed for health reasons in people who meet clinical criteria. That context matters when you're comparing names and claims online.

How do Mounjaro and Wegovy actually work differently?

Both slow gastric emptying and reduce appetite, but the receptor pathways diverge. Wegovy (semaglutide) is a GLP-1 receptor agonist, it mimics glucagon-like peptide-1, a gut hormone released after eating, to signal fullness and regulate blood sugar. Mounjaro (tirzepatide) adds a second pathway: it also activates GIP receptors (glucose-dependent insulinotropic polypeptide). That dual-agonist action is what makes tirzepatide the only medicine of its kind in the UK weight-management space right now.

In practice, what this receptor difference means for weight loss shows up in the trial data. SURMOUNT-1 recorded average body-weight reductions of around 20–21% at the highest tirzepatide dose over 72 weeks (in adults without diabetes, alongside a reduced-calorie diet). The STEP 1 trial for semaglutide 2.4 mg reported around 15% average weight reduction over 68 weeks. If you want to compare how each option stacks up, our full list of weight loss injections sets out the key details alongside the how weight-loss injections work page, which explains both mechanisms in plain terms if you want the deeper science.

One practical difference worth knowing: because tirzepatide can slow the absorption of oral medicines including the contraceptive pill, NHS guidance recommends using a non-oral contraceptive method for the first four weeks of Mounjaro treatment and for four weeks after each dose increase. No equivalent warning currently exists for semaglutide. Your prescriber will ask about this, raise it if they don't.

What does getting one of these injections actually involve?

Both Mounjaro and Wegovy are once-weekly subcutaneous injections, meaning a short, fine needle goes just under the skin (typically the abdomen, thigh or upper arm) on the same day each week. Treatment starts at a low dose (2.5 mg for tirzepatide; 0.25 mg for semaglutide) and the prescriber titrates upward roughly every four weeks, watching for tolerability. The pen itself is pre-filled: Mounjaro comes as a KwikPen containing four weekly doses; Wegovy as a single-use weekly pen.

If you're ordering through a regulated online pharmacy, what actually arrives is a plain, unbranded box via DPD tracked delivery, you'll get a notification on your phone before it reaches the door. The pen goes straight into the fridge (2–8°C). The Patient Information Leaflet inside covers every storage and administration detail; your prescriber's instructions take precedence over anything you've read online, including here.

Side effects are similar across both: nausea, vomiting, diarrhoea, constipation and reflux are most common, and tend to peak after starting or a dose increase before settling. The MHRA's NHS guidance on tirzepatide (Mounjaro) lists the full profile. In January 2026, the MHRA also issued a Drug Safety Update highlighting acute pancreatitis as a known, infrequent but serious risk, get urgent medical help for severe, persistent stomach pain that radiates to the back. You can report suspected side effects at the MHRA Yellow Card scheme.

For a broader look at injectable and oral options together, the weight-loss treatments page sets out what a clinical assessment with nume (with nume) covers and how to get started.

Does the name on the pen change who can get it?

Broadly, both medicines share a similar licensed eligibility framework: adults with a BMI of 30 or above, or 27 or above alongside at least one weight-related condition such as high blood pressure, high cholesterol, type 2 diabetes or obstructive sleep apnoea. Lower BMI thresholds apply for some ethnic backgrounds under UK guidance. But the licence is a floor, not a guarantee, a prescriber weighs your medical history, current medicines, contraindications and other factors that no BMI calculator captures.

NICE's appraisal of tirzepatide (TA1026, updated September 2025) sets the NHS criteria, which are stricter than the licensed ones: BMI 35 or above plus at least one weight-related comorbidity, in the current rollout cohort. Private prescribing follows the licensed criteria, assessed case by case. If you're unsure which name (or which route) fits your situation, the weight-loss injection overview covers eligibility in more detail, and a consultation with our prescribers costs nothing to start.

The cost picture varies by provider and dose, and it's worth reading about where you can buy weight-loss injections legally in the UK before making any decisions, particularly given the MHRA's warnings about counterfeit pens sold online without clinical oversight. If you want a quick reference while you research, our page listing the weight loss injections names available in the UK gives a concise overview of each option.