What types of weight loss injections are there in the UK?

Which medicines are actually licensed as weight loss injections in the UK?

Two injections hold a UK marketing authorisation specifically for weight management in adults: Mounjaro and Wegovy. That licensing detail matters because other injectable medicines sometimes discussed online, including Ozempic and Saxenda, are not licensed for weight loss in the UK in the same way. Other injectable medicines that come up in searches tend to be either diabetes treatments or older formulations with narrower indications.

Mounjaro contains tirzepatide, made by Eli Lilly. It works by activating two gut-hormone receptors simultaneously (GIP and GLP-1) which together reduce appetite, slow gastric emptying and influence blood-sugar regulation. It is the only dual-agonist weight-loss medicine with a UK licence. Treatment starts at 2.5mg weekly (a tolerability phase, not the therapeutic target) and can increase through six strengths up to 15mg, stepped by your prescriber roughly every four weeks. The SURMOUNT-1 trial, published in the New England Journal of Medicine, reported average body-weight reductions of around 20–21% at the 15mg dose over 72 weeks in adults with obesity.

Wegovy contains semaglutide and is made by Novo Nordisk. It targets the GLP-1 receptor alone. The standard maintenance dose has been 2.4mg weekly, though the MHRA approved a higher 7.2mg dose during 2026, which trials showed could deliver around 20.7% average weight loss. The STEP 1 trial reported roughly 15% average weight loss at 2.4mg over 68 weeks. If you are still weighing up your options, our guide covering what type of weight loss injections are available explains how each medicine works and where it fits. You can read a detailed breakdown of the types of weight loss injections and how their mechanisms compare.

Both carry a Black Triangle (▼) designation from the MHRA, meaning they are subject to additional monitoring while post-market safety data continues to accumulate.

How do the two injections differ in practice?

The clinical evidence is the clearest point of difference. In the SURMOUNT-5 trial (a head-to-head comparison published in the New England Journal of Medicine in 2025, involving 751 adults with obesity and no diabetes) tirzepatide produced a statistically greater average weight reduction than semaglutide 2.4mg over 72 weeks. That said, individual responses vary, and the higher 7.2mg semaglutide dose narrows the gap meaningfully. Which medicine is the better fit for a specific person is a clinical question, not one a comparison table can settle.

In terms of the injection itself, both arrive as pre-filled pens. The Mounjaro KwikPen holds four weekly doses in one device. Wegovy comes as individual weekly pens. Injection sites for both are the abdomen, thigh or upper arm, rotated each week. Both need refrigeration, though each has a limited window during which the pen can be kept at room temperature, the exact duration is set out in the Patient Information Leaflet inside each pack, and that is the figure to follow rather than any general rule.

When it comes to comparing costs, Eli Lilly raised Mounjaro's UK list price from September 2025, with the highest-dose pen now listed at around £330. Typical private market prices across both medicines range roughly £149–£375 per month depending on dose and provider. A legitimate price always includes the prescription and clinical assessment, checking what a quoted price covers is worth doing before committing.

Eligibility for both overlaps substantially: adults with a BMI of 30 or above, or 27 or above with at least one weight-related condition such as hypertension, high cholesterol, type 2 diabetes or obstructive sleep apnoea. Lower BMI thresholds apply for some ethnic backgrounds under UK guidance. Eligibility for NHS prescribing is considerably stricter, an overview of weight loss treatments sets out the private and NHS routes side by side.

What should you know about side effects before starting?

The side-effect profile for both injections is led by the gastrointestinal system. Nausea is the most commonly reported effect, followed by constipation, diarrhoea, indigestion, burping and reflux. Fatigue, headache and dizziness also appear in the trial data. Most people find these effects are at their worst in the first couple of weeks after starting or after a dose increase, then gradually settle. Starting at the lowest dose is partly about giving the digestive system time to adjust.

Injection-site reactions (mild redness or discomfort at the spot used) are worth rotating to minimise. Using a fresh needle each time and cleaning the site first are basic steps the Patient Information Leaflet covers. For safe disposal of used needles, a dedicated sharps container keeps things straightforward and meets local waste guidelines.

More serious but less frequent effects include acute pancreatitis. In January 2026 the MHRA issued a Drug Safety Update highlighting this risk across GLP-1 medicines: severe or persistent stomach pain that spreads to the back, with or without vomiting, warrants urgent medical attention. Gallbladder problems and signs of dehydration from severe nausea or vomiting should also prompt a call to your prescriber or GP. The MHRA's Yellow Card scheme is the right place to report any suspected side effect, from either medicine.

For women using oral contraceptives, tirzepatide in particular may reduce pill absorption during the first four weeks of treatment and for four weeks after each dose increase; adding a non-oral method during those windows is the recommendation from NHS guidance, as summarised on the NHS England weight-management injections page. Neither medicine is recommended during pregnancy, breastfeeding or when actively trying to conceive. Both are unlicensed for under-18s.

What actually happens when you get a prescription through a regulated service?

A legitimate prescription process for either injection starts with a clinical consultation, your medical history, current medicines, BMI and any relevant conditions are reviewed by a prescriber before anything is issued. At nume, that review is carried out personally by a GPhC-registered Independent Prescriber, not automated software, on the same day your consultation is submitted. You can check our pharmacy registration directly on the GPhC register (registration number 9012878).

Once approved, the pen is dispatched the same day if you order before 12pm Monday to Friday. It arrives via DPD the next working day in plain, unbranded packaging, the DPD tracking notification lands on your phone before the box does, which most people find reassuring when they're expecting temperature-sensitive medication. The pen goes straight into the fridge door when it arrives.

If you have questions before starting a consultation, our page on the 3 types of weight loss injections is a helpful starting point, and the frequently asked questions page covers the process in detail. And if anything comes up after you've started treatment, our clinical team is reachable seven days a week. Our clinical oversight means there's always a named prescriber behind any advice you receive.