All the weight loss injections currently licensed in the UK

What the trial evidence actually shows for each injection

The strongest data for any weight-loss injection in the UK currently sits with tirzepatide. In the SURMOUNT-1 trial (2,539 adults with obesity and no diabetes, 72 weeks) participants on the 15 mg dose lost an average of around 20–21% of their body weight, with some analyses reaching approximately 22.5%. That is the figure NICE cited when recommending tirzepatide in TA1026, published December 2024 and updated September 2025. In the SURMOUNT-5 head-to-head trial, published in the New England Journal of Medicine in 2025, tirzepatide produced greater average weight reduction than semaglutide 2.4 mg across 72 weeks in adults with obesity.

Semaglutide (Wegovy) has a longer prescribing history. The STEP 1 trial reported approximately 15% average weight loss at 68 weeks on the 2.4 mg maintenance dose. The MHRA approved a higher 7.2 mg dose on 14 April 2026, trials at that dose reported around 20.7% average weight loss over 72 weeks, narrowing the gap with tirzepatide 15 mg considerably.

Liraglutide (Saxenda), the older GLP-1 injection, showed more modest results in its pivotal trials and requires a daily rather than weekly injection. It remains licensed, but most UK prescribers and guidelines now favour the weekly options, and if you want to understand all the weight loss injections currently available, including where liraglutide sits alongside the newer options, our full overview covers each one. Check out our overview of the newer weight loss injections for more on how the landscape shifted.

How tirzepatide and semaglutide work differently in the body

Semaglutide mimics one gut hormone, GLP-1. It slows gastric emptying, signals fullness to the brain, and reduces appetite. Those effects are real and meaningful, which is why the clinical results are substantial.

Tirzepatide adds a second pathway. It activates both GLP-1 and GIP receptors simultaneously, making it the only dual-agonist weight-management medicine licensed in the UK. The combined signalling appears to drive greater appetite suppression and metabolic changes than either pathway alone, which is consistent with the larger average weight-loss figures in the trials.

In practice, both medicines start at a low dose to give the body time to adjust, tirzepatide starts at 2.5 mg, semaglutide at 0.25 mg. The prescriber increases the dose over several weeks based on how well you tolerate each step. Neither starting dose is the working dose; the real clinical effect builds as the dose is titrated upward. The NHS tirzepatide page gives a plain-language summary of how the medicine works and what to expect.

Side effects on both are led by the gastrointestinal system: nausea, loose stools, constipation, indigestion, and sometimes fatigue or headaches, particularly after starting or after a dose increase. These typically settle within days to a couple of weeks. Severe or persistent stomach pain (especially pain that reaches the back) warrants prompt medical attention given the known association between GLP-1 medicines and acute pancreatitis, which the MHRA highlighted in a January 2026 Drug Safety Update.

Who these injections are licensed for (and the NHS access picture

The private licence criteria (per the SmPCs) cover adults with a BMI of 30 or above, or 27 and above if at least one weight-related condition is present) for example, high blood pressure, high cholesterol, obstructive sleep apnoea, prediabetes, or type 2 diabetes. Lower BMI thresholds apply for some ethnic backgrounds under UK guidance. BMI alone does not guarantee a prescription; the prescriber reviews the full clinical picture, and our guide to what are the 3 weight loss injections most commonly prescribed in the UK breaks down how eligibility criteria differ between tirzepatide, semaglutide, and liraglutide. See the guide to what weight loss injections are for a fuller breakdown of how eligibility works.

NHS access follows stricter phased criteria. Tirzepatide became available through GP practices from April 2026 under the new GP contract, initially for patients with a BMI of 40 or above and four or more qualifying conditions. The second cohort (BMI 35–39.9 with four or more conditions) opened in June 2026. Semaglutide (Wegovy) on the NHS is available through specialist weight management services under NICE TA875, though waiting lists are commonly long. The NHS route is real; it is also slow for most people right now.

Private prescription through a regulated online pharmacy offers a faster path for those who are clinically suitable but do not meet the current NHS thresholds or do not want to wait. If you want to explore how to get weight loss injections through a private route, the practical steps are simpler than many people expect, but the clinical assessment is exactly the same standard.

What actually happens when you order through a regulated pharmacy

A legitimate supply chain matters here. Counterfeit weight-loss pens have been seized in large quantities across the UK, fake pens have in some cases contained insulin rather than the medicine on the label, with serious consequences. The MHRA has issued repeated warnings; only buy from a pharmacy you can verify on the GPhC register. Sellers offering these medicines without a prescription, or at prices dramatically below the market rate, are a red flag worth taking seriously.

At nume, every consultation is read by a GPhC-registered Independent Prescriber, not software. Orders placed before 12pm on working days are dispatched the same day once approved, via DPD tracked delivery in plain, unbranded packaging, your pen arrives the next working day, and you can follow it on your phone like any other parcel. A one-off price covers the consultation, prescription, treatment, and delivery; there is no subscription and no auto-renewal.

The cost of treatment varies by dose and provider. Our treatment options page shows current pricing clearly, and if you have questions about anything before starting, our FAQs cover the queries our prescribers hear most often.