The top 3 weight loss injections licensed in the UK right now

The biggest myth: that all weight loss injections work the same way

A question our prescribers hear most weeks is whether the injections on the market are essentially interchangeable — different brands for the same thing. They are not. The mechanism matters, and it shapes both the trial results and the side-effect profile you might experience.

Liraglutide (Saxenda, by Novo Nordisk) was the first injectable approved in the UK specifically for weight management. It activates GLP-1 receptors, slowing gastric emptying and reducing appetite, but it is injected daily rather than once weekly and its average weight loss in trials sat around 5–8% of body weight. That is still clinically meaningful, but it is a different league from the newer medicines.

Semaglutide (Wegovy, also Novo Nordisk) is a once-weekly GLP-1 agonist. In the STEP 1 trial published in the New England Journal of Medicine, adults taking the 2.4mg maintenance dose achieved around 15% average body-weight reduction over 68 weeks. A higher 7.2mg dose has since been approved by the MHRA, with trial data suggesting around 20.7% average loss over 72 weeks. Once-weekly dosing made it a step change in tolerability and convenience over its predecessor. You can read more about how these injections compare in our overview of weight loss injections.

Tirzepatide (Mounjaro, by Eli Lilly) is the newest and, on current evidence, the most effective of the three. It is the only dual-agonist in this group, activating both GIP and GLP-1 receptors. In SURMOUNT-1, the largest phase-3 trial, participants at the 15mg dose achieved around 20–21% average weight loss over 72 weeks. The SURMOUNT-5 head-to-head trial, published in 2025, found tirzepatide produced greater average weight reduction than semaglutide 2.4mg over the same period. Different mechanism, meaningfully different numbers. If you want a broader view of how the field sits right now, our guide to the top weight loss injections and their evidence base covers each option in detail.

Which of the three is right for you (and what eligibility looks like

UK licensing for all three follows a similar pattern: adults with a BMI of 30 or above, or 27 and above where at least one weight-related condition is present) such as high blood pressure, raised 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 an approval guarantee. A prescriber assesses the whole picture: your medical history, any medicines you already take, contraindications, and your goals.

Liraglutide requires a daily injection; some people find daily dosing harder to sustain over months. Semaglutide and tirzepatide are both weekly, but tirzepatide's dual mechanism makes it, on average, more potent. For people using oral contraceptives, tirzepatide carries a specific interaction note: an additional non-oral contraceptive method is recommended for the first four weeks of treatment and for four weeks after each dose increase, because GLP-1 medicines can slow absorption of oral medicines, including the pill. NHS England's guidance on weight management injections covers this interaction, and HRT considerations, in full.

Pregnancy, breastfeeding, and actively trying to conceive are situations where none of the three weight loss injections currently available in the UK is recommended. Under-18s are not a licensed population for weight-management use. These are hard clinical lines, not cautious suggestions. If you are unsure where you stand, our frequently asked questions cover common eligibility scenarios.

Cost, NHS access, and what a private route involves

NHS availability differs sharply across the three. Wegovy (semaglutide) is commissioned through specialist weight management services under NICE guidance, and waiting times can be substantial. Tirzepatide received a positive NICE recommendation in December 2024 (Technology Appraisal TA1026) and NHS rollout is phased, initially for people with BMI 40 and above alongside multiple qualifying conditions, broadening progressively through 2026 and 2027. Liraglutide has no equivalent NICE technology appraisal for weight management, making NHS access less straightforward still.

Private treatment is the route most people take when they do not meet the current NHS criteria or prefer not to join a waiting list. If you are weighing up your options, our rundown of the top 5 weight loss injections available privately is a useful starting point for comparing what is currently on the market. The cost of private weight loss injections varies by medicine and dose; if you want to understand what goes into an honest private price, our page on how much weight loss injections cost sets out what to look for and what legitimate pricing actually includes. It also flags why an unusually low price should raise questions rather than prompt a click.

For context, Eli Lilly adjusted Mounjaro's UK list price in September 2025, with reported private prices for the highest dose typically ranging from around £149 to £375 per month depending on provider and dose. Those figures are widely reported and hedged here because they reflect a market snapshot, not a guaranteed current rate. The right comparison across providers is not which is cheapest, but which includes clinical oversight, a registered prescriber, a pharmacy you can verify, and support if something concerns you. Our guide to the top 10 weight loss injections covers a wider range of options if you want to explore the full landscape before making a decision.

Saxenda (liraglutide) is not dispensed by nume. If tirzepatide or semaglutide may be clinically appropriate for you, check your eligibility with our prescribers, who review every consultation personally and the same day.