The latest weight loss injection available in the UK

The biggest misconception: 'newest' does not mean 'strongest for everyone'

A question our prescribers hear most weeks is some version of: "Which injection is the latest one? Should I be on that one?" The assumption underneath it is reasonable, if a medicine is newer, it must be better. The reality is more nuanced. Tirzepatide was the later of the two to receive a UK weight-management licence (2023, versus semaglutide's 2021 approval as Wegovy), and in the SURMOUNT-5 head-to-head trial, published in the New England Journal of Medicine in 2025, it did produce greater average body-weight reduction than semaglutide 2.4mg over 72 weeks. But Novo Nordisk's newer 7.2mg Wegovy dose (approved by the MHRA in April 2026) narrows that gap considerably, with trials reporting roughly 20.7% average weight loss. Both medicines are licensed, both are clinically serious options, and which suits a specific person depends on their health history, other medicines they take, and how they respond. Recency alone is not a prescription.

It is also worth correcting a related myth: these are not cosmetic treatments. The MHRA and DHSC have been explicit that GLP-1 medicines are not assessed or licensed for quick or cosmetic weight loss. They are medicines for a clinical condition, prescribed to people who meet defined criteria.

How the two licensed injections actually work

Semaglutide, the active ingredient in Wegovy, mimics a gut hormone called GLP-1. When it binds to GLP-1 receptors in the brain and digestive system, appetite falls and the stomach empties more slowly, most people find meals feel satisfying with noticeably less food. The NHS medicines information on semaglutide covers this mechanism in plain language for patients.

Tirzepatide does the same thing, and adds a second pathway. It is the only licensed weight-loss injection in the UK to activate GIP receptors alongside GLP-1 receptors, and if you want to understand how that dual mechanism plays out in practice, our page on the m injection for weight loss goes into the detail behind tirzepatide's second receptor pathway. This dual action is part of why its trial results have tended to run ahead of semaglutide's at comparable stages. In SURMOUNT-1, participants on 15mg tirzepatide lost an average of roughly 20–21% of body weight over 72 weeks. That figure comes from a clinical trial in controlled conditions; individual results vary, and a prescriber will not quote a number as a guarantee.

Both injections are titrated gradually. Treatment starts at a low dose (2.5mg for tirzepatide) and increases over several months. The slow climb exists primarily to give the body time to adjust and to keep gastrointestinal side effects manageable. The pace is set by the prescriber, not the patient.

Who these injections are licensed for, and the route to access them

Both tirzepatide and semaglutide carry a UK licence for adults with a BMI of 30 or above, or a BMI of 27 or above alongside at least one weight-related condition such as high blood pressure, type 2 diabetes, high cholesterol, or obstructive sleep apnoea. Lower BMI thresholds apply for some ethnic backgrounds under UK guidance. BMI is a starting point, not a guarantee: a prescriber reviews the full clinical picture before deciding whether treatment is appropriate.

On the NHS, access to both medicines is phased and criteria are strict. For tirzepatide, NICE recommends it for adults with a BMI of 35 or above plus at least one weight-related comorbidity, under specific commissioning arrangements; the rollout is expanding gradually through 2026 and 2027. Many people who are clinically eligible turn to regulated private services rather than wait, and some prefer to explore a weight loss injection without subscription, which suits those who would rather not commit to an ongoing plan before they have tried treatment. You can explore what a private consultation involves on our weight loss injection overview, or look at how the two medicines compare on the page that walks through which injection may suit you.

For anyone researching which injections have the strongest evidence base, the trial data is public and the licensed indications are clear. Speed of results, however, is a function of clinical suitability and adherence, not which medicine has the more recent approval date.

Side effects and what to watch for

The side-effect profile of both injections is dominated by gastrointestinal symptoms: nausea, loose stools, constipation, indigestion, and burping are the most common. These tend to be most noticeable in the first days after a dose or a dose increase, and for many people they settle within a couple of weeks. Taking the injection with a light meal and staying well hydrated helps most people get through the early weeks.

Pancreatitis is a less common but serious risk. Severe stomach pain that radiates through to the back, with or without vomiting, needs urgent medical attention. The MHRA highlighted this in a Drug Safety Update in January 2026. Patients and carers can report suspected side effects directly through the Yellow Card scheme at yellowcard.mhra.gov.uk.

Neither injection is recommended during pregnancy, while breastfeeding, or when trying to conceive. They are not licensed for under-18s. Women on oral contraceptives starting tirzepatide should use a non-oral method of contraception for the first four weeks of treatment and for four weeks after each dose increase, as gut slowing can reduce pill absorption. These are the sorts of detail that a prescriber works through with each patient, not generalisations from a web page.

If you are weighing up what private treatment costs and what that price covers, that information is available separately. For anyone ready to talk to a clinician, speak to our prescribers through a free consultation, reviewed the same day by a GPhC-registered Independent Prescriber, not a screening algorithm.