Slim shot injections for weight loss: the decision in plain terms

Which injection are people actually talking about?

The term 'slim shot' isn't a medical one, but in practice it refers to the two GLP-1 class injections that hold a UK weight-management licence: Mounjaro (tirzepatide, made by Eli Lilly) and Wegovy (semaglutide, made by Novo Nordisk). Tirzepatide is a dual GIP and GLP-1 receptor agonist, meaning it targets two pathways involved in appetite regulation and blood-sugar control. Semaglutide targets the GLP-1 pathway only. Both slow gastric emptying and reduce hunger signals, but they do so through slightly different biology.

Neither is a single injection. Both are once-weekly regimens using a pre-filled pen: Mounjaro starts at 2.5mg and is titrated upward by the prescriber; Wegovy starts at 0.25mg and works toward a maintenance dose of 2.4mg (or, as of April 2026, up to 7.2mg with the newly approved higher-dose pen). If you're curious about the broader range of injection shots for weight loss that are available and how they differ from one another, that's a useful place to build your understanding before you ask a prescriber anything.

You can read more about how the two medicines compare on our slimming injections overview, which covers the mechanism differences in more detail. For now, the most important thing to know is that Ozempic, though it contains semaglutide, is licensed for type 2 diabetes (not weight loss) and is not the same as Wegovy.

What the evidence actually says about results, and what it doesn't

The clinical trial data here is worth taking seriously. In the SURMOUNT-1 trial, tirzepatide produced average weight reductions of around 20–21% at the highest dose over 72 weeks, in adults with obesity and no diabetes. The STEP 1 trial reported roughly 15% average reduction with semaglutide 2.4mg over 68 weeks. These are clinically meaningful differences from placebo, published in the New England Journal of Medicine.

What the trials don't tell you is how you specifically will respond. Results vary by individual. Both trials enrolled participants who also followed reduced-calorie diets and increased their activity, the injections worked alongside those changes, not instead of them. The medicines reduce appetite, which makes it easier to sustain a deficit, but protein intake, hydration and staying physically active all matter more, not less, once you're on treatment.

Stopping the injection tends to reverse some weight loss over time, so the question of how long you'd stay on treatment is part of the prescriber conversation from the beginning. Our guide to how many injections are involved covers what a typical treatment course looks like. No reputable service guarantees a specific outcome; the evidence gives a range of probabilities, not a promise.

Who can access these injections, and how

The licensed eligibility criteria for both medicines are set by the manufacturer and confirmed by the MHRA: adults with a BMI of 30 or above, or 27 or above if at least one weight-related condition is present, such as high blood pressure, high cholesterol, prediabetes or obstructive sleep apnoea. Lower BMI thresholds apply for some ethnic backgrounds under UK guidance. BMI alone doesn't determine suitability; a prescriber assesses your full health picture, including medications you already take and any contraindications.

On the NHS, access to tirzepatide is currently phased and criteria are strict, the NICE appraisal (TA1026) sets minimum thresholds that most people searching this topic won't meet yet. A private prescription through a regulated online pharmacy is the route available to most people right now, and if you want a clearer picture of the options, our page on weight loss injections explains the landscape in plain terms. Whatever route you take, the prescription must come from a registered prescriber who has reviewed your case, any seller offering these injections otherwise is operating outside UK law, and the MHRA has warned publicly about counterfeit pens that have caused serious harm.

Cost is a factor for most people, and our cost context page addresses what UK private treatment realistically involves and what to watch for in low-price listings.

What the process looks like at a regulated pharmacy like nume

If you decide to explore a private prescription, the process at a GPhC-registered pharmacy like ours starts with a free consultation, no upfront payment before a clinician has looked at your case. A GPhC-registered Independent Prescriber reads your answers the same day; if you're clinically suitable, your prescription is issued and your order dispatched. Orders placed before 12pm on weekdays go out the same day via DPD, tracked to your door in plain, unbranded packaging. That's what actually arrives: a small, discreet box, your pen, and the information you need to use it safely.

Every repeat order goes through the same clinical review, not an automated renewal. If you have questions about your treatment between orders, prescriber-led aftercare is available seven days a week. Our about us page covers the pharmacy's registration and how we're set up. Our FAQs address the questions people ask most often before they start, including a section on what weight loss shot injections actually involve in practice, which many people find useful before their first consultation.

If you'd like to talk through which option fits your situation, speak to our prescribers, it starts with a free consultation, and there's no obligation to proceed.