Weight loss injections in the UK: the honest, complete picture

Step by step: the legal route to a weight loss injection

There's only one lawful way to get these medicines in Britain, and it's worth knowing the sequence before you start. First, a clinical consultation. In the UK, weight loss injections are Prescription-Only Medicines, so a prescriber has to assess you before anything is dispensed. That's the law under the Human Medicines Regulations, and any service skipping it should worry you.

At nume the order runs like this. You complete a free online consultation, answering questions about your health, weight history and medications. A GPhC-registered Independent Prescriber reads your answers the same day, not a piece of software making a snap decision. We verify your identity with photo ID and confirm your weight on a short video, in line with pharmacy guidance. If the prescriber judges treatment clinically suitable, we dispense from our own UK pharmacy.

Then it ships. Order and get approval before 12pm on a weekday and your treatment is dispatched the same day, arriving free the next working day by DPD. What lands on your doorstep is a plain, unbranded box you can track on your phone, with the pen inside kept cool for transit. No shop counter, no waiting room. If you'd rather understand the process in more detail first, our guide to how weight loss injections are given covers the practical side once you have your pen.

Repeat orders aren't automatic. Every one is clinically re-reviewed, so there's no subscription quietly renewing in the background. It's a small thing that matters for a prescription medicine.

What weight loss injections actually do inside the body

These medicines mimic hormones your gut releases after eating. Semaglutide, the drug in Wegovy, is a GLP-1 receptor agonist: it acts on a single hormone pathway that governs appetite and blood sugar, slowing how quickly your stomach empties and helping you feel full for longer. The NHS explains this mechanism plainly on its semaglutide medicines page.

Tirzepatide, the drug in Mounjaro, goes a step further. It's a dual agonist, activating both the GIP and GLP-1 receptors, and it's currently the only dual-action weight loss injection licensed in the UK. Two hormone pathways rather than one is thought to be why, in head-to-head research, it produced larger average reductions. You can read more about the broader class of GLP-1 weight loss injections and how they compare.

The practical effect is straightforward. Appetite falls, portions shrink without white-knuckle willpower, and cravings quieten. That's why the medicines are only ever licensed alongside dietary change and more movement, not instead of them. They give you a fairer fight, not a free pass.

Importantly, weight is a health condition shaped by biology, hormones and environment, not a simple matter of effort. Treating it with a medicine that targets those hormones is a legitimate clinical approach, which is why the MHRA and NICE assess and recommend these drugs for the right patients. If you want the wider context, our overview of medical weight loss options sets the scene.

Mounjaro and Wegovy: which weight loss injections are licensed here

People searching for the "best weight loss injections UK" usually want a name. Honestly, there are two that count for weight management, and "best" depends on your body and history, not a league table.

Mounjaro (tirzepatide) is made by Eli Lilly and comes as a pre-filled KwikPen, each holding four weekly doses. UK strengths run 2.5, 5, 7.5, 10, 12.5 and 15mg. Treatment starts at 2.5mg, a settling-in dose whose job is to let your system adjust before any therapeutic strength, and the prescriber steps you up gradually, usually every four weeks. It's licensed for weight management and for type 2 diabetes.

Wegovy (semaglutide) is Novo Nordisk's once-weekly pen, moving through 0.25, 0.5, 1.0, 1.7 and 2.4mg. In January 2026 the MHRA approved a higher 7.2mg maintenance dose, and in April 2026 a dedicated single-dose 7.2mg pen for adults with a BMI of 30 or more. Which specific dose or pen format is right, and what's available to you, is confirmed at consultation rather than promised up front.

A frequent mix-up worth clearing: Ozempic and Rybelsus contain semaglutide too, but they're licensed for type 2 diabetes, not weight loss, so they aren't the same thing as Wegovy. And the Mounjaro weight loss injection is what people sometimes mean by loose nicknames. Both licensed injections carry the Black Triangle symbol, meaning the MHRA is gathering extra safety data, as noted in the product information on the electronic medicines compendium.

Who these injections are licensed for, and who they're not

Eligibility isn't a single number. The licensed threshold for private treatment is a BMI of 30 or above, or 27 or above with at least one weight-related condition such as high blood pressure, high cholesterol, prediabetes, type 2 diabetes, obstructive sleep apnoea or osteoarthritis.

Those cut-offs shift for some groups. Under UK guidance, the BMI threshold is set around 2.5 kg/m² lower for people of South Asian, Chinese, other Asian, Middle Eastern, Black African or African-Caribbean backgrounds, because health risk arrives at a lower BMI. You can check where you stand with the NHS BMI calculator, though the number is only a starting point. Our page on what weight you need to qualify goes deeper into the thresholds.

BMI alone never guarantees a prescription. A prescriber weighs your full history, current medicines and any red flags before deciding, which is exactly why the clinical assessment exists rather than a box-ticking form.

Some people should not use these injections. They aren't licensed in pregnancy, aren't recommended while breastfeeding or when you're trying to conceive, and aren't for anyone under 18. A history of medullary thyroid cancer, MEN2 syndrome, or previous pancreatitis needs a frank conversation with the prescriber, and certain gut conditions may rule treatment out. If you take the combined pill, note that tirzepatide can temporarily reduce how well it's absorbed, so NHS guidance advises an added barrier method for the first four weeks and after each dose increase. None of this is a reason to be discouraged; it's a reason to be assessed properly.

What the trials actually found about weight loss

Numbers help set expectations, provided they're the real ones. In the SURMOUNT-1 trial, published in the New England Journal of Medicine and involving thousands of adults, tirzepatide produced average body-weight reductions of roughly 20 to 21% at the 15mg dose over 72 weeks, alongside diet and activity support.

Semaglutide's landmark STEP 1 trial reported around 15% average loss over 68 weeks at the 2.4mg dose. The newer 7.2mg dose narrows the gap, with trial data showing roughly 20.7% over 72 weeks. And in SURMOUNT-5, a head-to-head study published in the New England Journal of Medicine in 2025, tirzepatide produced greater average weight reduction than semaglutide 2.4mg across 72 weeks in adults with obesity and no diabetes.

Two honest caveats. These are averages, so individual results vary widely, and the figures come from trials where participants also changed diet and activity. The medicines aren't magic, whatever the tabloid "skinny jab" headlines suggest. NICE has assessed both, recommending tirzepatide in its technology appraisal TA1026 and semaglutide under TA875, each with specific criteria and review points.

NICE also builds in a checkpoint. If someone loses less than 5% of their body weight after six months at the highest tolerated dose, continuing treatment is reviewed. That's a sensible test of whether a medicine is earning its place for you, rather than a promise it always will.

Side effects: what's common, what's rare, when to get help

Most side effects are digestive and predictable. Nausea, an unsettled stomach, diarrhoea or constipation, reflux, burping, tiredness, headache and mild injection-site reactions are the usual list. They tend to show up when you start or step up a dose and often ease within a few days to a couple of weeks as your body adjusts. Eating smaller, less fatty meals and keeping hydrated generally helps.

There are rarer but serious signals worth knowing. On 29 January 2026 the MHRA issued a Drug Safety Update flagging acute pancreatitis as an uncommon but potentially serious effect of GLP-1 medicines: seek urgent medical help for severe, persistent stomach pain that may spread through to your back, with or without vomiting. Other reasons to get checked promptly include gallbladder symptoms, signs of dehydration or kidney trouble after heavy vomiting or diarrhoea, an allergic reaction, or any low mood or thoughts of self-harm.

You can report a suspected side effect through the MHRA Yellow Card scheme, which also lets you flag suspect sellers. Doing so genuinely helps the safety picture for everyone.

This is where seven-day aftercare earns its keep. Side effects rarely arrive at a convenient hour, so having prescribers you can reach when a symptom worries you turns a scary moment into a manageable one. It's a question our prescribers hear most weeks, and having someone to answer it matters more than any glossy promise.

NHS or private: how access really differs

Plenty of people ask why they can't just get these on the NHS. You can, but the criteria are strict and rolling out in phases. Under NICE TA1026, tirzepatide is being introduced through the NHS in stages: as of mid-2025 it reached adults with a BMI of 40 or more plus four or more of five weight-related conditions, with a second group (BMI 35 to 39.9 with four-plus conditions) activated from June 2026, and further phases to follow.

From April 2026 GP practices may prescribe under the new GP contract, but participation is optional, so what's available depends heavily on your practice and area. Wegovy on the NHS runs through specialist weight management services under TA875, capped at two years, and waiting lists are often long. NHS England sets out the pathway and the wrap-around support on its weight management injections page.

None of that is a criticism of the NHS; it's simply how a limited resource is being rationed to those at highest risk first. If you don't meet the phased criteria, or can't face the wait, a regulated private route is the alternative. Our explainer on NHS access to weight loss injections lays out the phases in full, and there's a separate guide for readers in Northern Ireland, where access differs. Criteria also differ across Scotland and Wales.

What weight loss injections cost, and why cheapest is the wrong test

Cost matters, and we'll be plain about it. Private weight loss treatment in the UK is priced per pen or per month and varies by dose and provider. After Eli Lilly raised Mounjaro's UK list price from 1 September 2025, reported private prices have typically ranged from around £149 to £375 a month depending on dose and clinic.

Here's the catch with headline figures: they often leave things out. A low sticker price can exclude the consultation fee, the prescription charge, delivery and any aftercare, so the real total is higher than it first looks. A legitimate price always includes a proper clinical assessment, because that's the law.

nume charges one transparent price that folds in the free consultation, the prescription, the medicine, free next-working-day tracked delivery and seven-day aftercare, with no subscription and no auto-renewal. We're openly not the cheapest listing you'll find, and that's a choice. For a prescription medicine, price is the wrong yardstick anyway; a genuine supply chain and real clinical oversight are what keep you safe. If budget is your main concern, our honest take on the cheapest weight loss injections is worth reading before you decide.

Which brings up counterfeits. The MHRA has repeatedly warned about fake pens sold online and through social media; a 2025 enforcement effort seized around 20 million doses of illegally traded weight-loss medicines, and fake pens have been found to contain insulin. The safe rule is simple: use a pharmacy you can check on the register, and treat any seller offering these medicines without a clinical assessment as a red flag.

How to check a service is legitimate before you order

One habit protects you more than any review score: verify the pharmacy. Every UK pharmacy has a registration you can look up on the General Pharmaceutical Council register. nume's GPhC premises registration is 9012878, and you can confirm it directly on the GPhC register. If a website selling injections can't show you a registration to check, walk away.

The warning signs are consistent. Sellers offering these medicines without any health questions, social-media accounts taking orders, prices far below the market, or "discount codes" from unknown sources all point the wrong way. Genuine services ask about your health because they legally must. If you'd like to understand who's behind our clinical decisions, you can read about our clinical team and how nume operates.

It's also worth knowing what these injections are not. B12, B6 and L-carnitine injections are sometimes marketed for weight loss, but they aren't the same as the licensed GLP-1 medicines and aren't licensed weight loss treatments in the UK; our note on B12 injections and weight loss explains the difference. If you're weighing up your options and want a prescriber's read on suitability rather than a sales pitch, that's exactly what a consultation is for. Speak to our prescribers through our free weight loss consultation and get an honest answer about whether treatment fits your situation.