The Best Rated Weight Loss Injections Available in the UK

Step 1, understand what separates Mounjaro and Wegovy

Mounjaro activates two receptors involved in appetite regulation: GIP and GLP-1. Wegovy works on one. That dual action is why, in a 72-week head-to-head trial (SURMOUNT-5, published in the New England Journal of Medicine in 2025), tirzepatide produced a larger average weight reduction than semaglutide 2.4mg. In the earlier SURMOUNT-1 trial, participants taking 15mg tirzepatide lost around 20–21% of body weight on average, figures that put it among the top rated weight loss injections in this licensed class.

Wegovy's trial data is also substantial. The STEP 1 study, run over 68 weeks, showed roughly 15% average weight reduction at the 2.4mg maintenance dose, and a higher 7.2mg dose approved by the MHRA in early 2026 brings semaglutide's results closer to tirzepatide's. You can read more about how the two medicines differ on our comparison of weight loss injection options page.

A question our prescribers hear most weeks: "Is one injection definitely better than the other?" The honest answer is that the trial numbers favour tirzepatide on average weight loss, but individual response varies, tolerability matters, and a prescriber weighs your full history before recommending either. The comparison table is a starting point, not a verdict.

Step 2, check whether you meet the eligibility criteria

Both injections are licensed for adults with a BMI of 30 or above, or a BMI of 27 or above alongside at least one weight-related health condition such as high blood pressure, type 2 diabetes, high cholesterol or obstructive sleep apnoea. Lower BMI thresholds can apply for people from some ethnic backgrounds under UK clinical guidance. The weight loss injection overview covers the licensing criteria in more detail.

NICE's appraisal of tirzepatide (TA1026) recommends it for adults with a BMI of 35 or above plus at least one weight-related comorbidity on the NHS, with phased rollout criteria being expanded through 2025–2027. Private eligibility follows the licensed indications directly, so the BMI 30 threshold applies, but eligibility is never just a number. The prescriber's assessment of your overall health is what determines suitability.

Mounjaro treatment starts at the 2.5mg dose, which exists to let your body adjust rather than to produce weight loss immediately; doses are then increased by the prescriber, typically in four-week steps. Wegovy follows a similar graduated schedule, starting at 0.25mg.

Step 3, confirm the injection is being supplied safely

The MHRA has been clear that fake weight loss pens are circulating in the UK, some containing substances as dangerous as insulin. In 2025 alone, around 20 million doses of illegally traded weight-loss medicines (roughly £45 million street value) were seized, and the first illicit manufacturing site producing counterfeit tirzepatide pens was raided. The safest check is straightforward: look up any online pharmacy on the GPhC register before ordering. Sellers offering these medicines without a prescription, or advertising discount codes and unusually low prices, are significant red flags.

Storage matters too. Both injections are refrigerated medicines with specific room-temperature limits; the Patient Information Leaflet is the authoritative source for exact windows. Our guide on refrigerating weight loss injections explains what to know before you travel or step away from home. For safe disposal of used pens, a sharps container is worth having before you start.

Step 4, what a regulated private consultation looks like

For most people weighing up their options, the practical question is how to get a genuine, clinically supervised prescription without a long wait. The weight loss injections page explains the landscape of routes, from NHS specialist services (which carry waiting lists) to regulated private pharmacies. On the private route, a GPhC-registered prescriber reviews your consultation, a real clinician reading your answers, not automated software making the call.

If you are thinking about cost alongside clinical factors, the full cost breakdown for weight loss injections covers what a legitimate price typically includes: consultation, prescription, clinical review and delivery. For a prescription medicine, the cheapest listing answers the wrong question. The right question is whether the supply chain, the prescriber and the aftercare are genuine.

You can also explore broader weight loss treatment options if you are still deciding between approaches, or visit our about us page to see how our pharmacy is registered and regulated. When you are ready to discuss your situation with a prescriber, speaking to our clinical team is the next step.