Weekly Weight Loss Injection UK Guide (October 2026)

01 · The core answer

What is the weekly injection for weight loss, and is it right for you?

The weekly injection for weight loss is a once-a-week prescription medicine that helps you feel fuller sooner and less hungry between meals. In the UK the two names you will see most are Mounjaro and Wegovy. Mounjaro is the brand name for tirzepatide, a once-weekly injectable made by Eli Lilly, licensed for weight management in adults and for type 2 diabetes.¹ Wegovy contains semaglutide, a single-action GLP-1 medicine, and its licensed maintenance dose for weight management is 2.4mg once weekly.¹⁸

They are not a shortcut, a supplement or a quick fix. Treatment is used alongside a reduced-calorie diet and increased physical activity, and individual results vary.¹ If a website, social post or seller promises dramatic weight-loss claims within days, treat that as a warning sign. Genuine treatment is gradual, reviewed by a clinician and supplied by a registered pharmacy.

• Are you an adult looking for medically supported weight management, rather than a short-term diet?
• Are you ready to change how you eat and move, with the injection supporting that effort?
• Are you comfortable with a once-weekly injection under the skin, using a pre-filled pen?
• Can you commit to ongoing reviews, because the dose is adjusted according to how you respond and tolerate it?

If you answered yes, the second decision is which route to take: NHS or private. NHS access to Mounjaro is being phased in over several years. NICE recommends it for adults with a BMI of at least 35 plus at least one weight-related condition, and the NHS primary-care rollout began in June 2025 with the highest-need groups first (initially BMI 40+ with four or more qualifying conditions). Full rollout is expected to take years, which is why many people who meet the licensed criteria choose regulated private treatment rather than waiting.⁴⁶ Ask your GP about the NHS route, and if you would rather go private, our weight loss clinic explains the process.

02 · Choosing

Which weekly weight loss injection should you consider?

Your prescriber should help you choose, because the right option depends on your health history, how you tolerate treatment and what you can access. Both Mounjaro and Wegovy are licensed once-weekly medicines. The main difference is the mechanism: tirzepatide activates both GIP and GLP-1 receptors, which distinguishes it from single-action GLP-1 medicines such as semaglutide.¹

Daily injections such as liraglutide (Saxenda, and products such as Erly) are a different category: they are supplied at a concentration of 6mg per millilitre and are taken every day, unlike the once-weekly options above. If you want to see where Mounjaro sits in more detail, our Mounjaro weekly injection guide goes deeper, and our diabetes and weight loss injection guide explains how the same medicines are used for type 2 diabetes.

03 · What to do next

What should you do next?

If you are ready to explore treatment, the next step is a free online consultation, reviewed by a GPhC-registered prescriber. You can read current dose prices and start on the Mounjaro pen page. Your first 2.5mg pen costs £129.99 with code FIRST40 (standard price £169.99), and every later order is £25 off the standard price (code DOSE25).

If you are not ready, that is fine. Accuracy matters more than speed with a prescription treatment, and a prescriber can only approve it if it is suitable for you. Payment is taken when you place the order; if the prescriber decides the treatment is not suitable, the order is refunded automatically in full.

04 · What these injections are

What a weekly weight loss injection actually is

A weekly weight loss injection is a prescription medicine given as a small injection under the skin once a week. Mounjaro is the brand name for tirzepatide, a once-weekly injectable prescription medicine made by Eli Lilly. In the UK it is licensed for weight management in adults and for type 2 diabetes. It comes as a pre-filled multi-dose pen (KwikPen) in six strengths: 2.5mg, 5mg, 7.5mg, 10mg, 12.5mg and 15mg.¹

The pen does the measuring for you. You do not draw up liquid from a vial or work out volumes. You dial the dose, inject, and put the cap back on. That simplicity is a large part of why the once-weekly format is popular: it fits around work and family, and you only have to think about it on one day.

It also helps to separate these licensed medicines from everything else sold with similar language. Low-cost supplements and so-called natural alternatives are available cheaply without assessment and have no clinical oversight. They do not carry the licence, the trial programme or the prescriber review that a weekly injection does. If a product is sold with dramatic weight-loss claims and no consultation, treat it with caution.

Who makes the decision

In the UK, Mounjaro is supplied only after an online consultation reviewed by a GPhC-registered prescriber, and it is used alongside a reduced-calorie diet and increased physical activity. Individual results vary.¹ That review is the safeguard: your prescriber looks at your health history, your current medicines and whether treatment is appropriate.

You may also wonder about names you have seen online. Other brand-style names and informal labels circulate widely, and some are not products you can lawfully buy in the UK. Our pages on the Majorna injection and the retro weight loss injection explain how to tell a genuine licensed medicine from a misspelling or a marketing label. If you cannot find a product on the UK product information or the pharmacy register, do not buy it.

What the injection does not do

It does not replace food choices or movement, it does not act instantly, and it does not work in the same way for everyone. Some people notice appetite change early; others feel little until a higher dose. Both patterns are normal, and your prescriber will guide the pace.

05 · How it works

How weekly injections reduce appetite

Weekly weight loss injections work by copying natural gut hormones that are released after you eat, which makes you feel fuller sooner and less hungry between meals. Tirzepatide is the first treatment of its kind to activate two natural gut-hormone receptors at once: GIP and GLP-1. Together these help regulate appetite, slow how quickly the stomach empties, and improve the way the body responds to insulin.¹

In practice, most people feel fuller sooner and less hungry between meals, which supports a reduced-calorie diet.¹ The medicine changes the conditions under which you make food decisions; it does not make the decisions for you. Portions that once felt normal may feel too large, and cravings may be quieter, but you still need to eat enough protein, stay active and build habits that outlast treatment.

Single-action and dual-action

This dual action is what distinguishes Mounjaro from single-action GLP-1 medicines such as semaglutide (Wegovy/Ozempic).¹ Wegovy works through the GLP-1 pathway only. Neither is automatically better for every person. The sensible question is which one a prescriber considers suitable for you, and which one you tolerate and can obtain.

If you see a headline claiming one medicine "beats" another, check which trial the claim comes from and whether the two medicines were actually compared in the same study.

Why slower digestion matters

Slower stomach emptying is part of why you feel full for longer. It is also part of why early side effects such as mild nausea can occur in the days after an injection. Mild nausea, altered appetite and tiredness in the first days after each injection are the commonest early effects and usually settle.¹ If symptoms are severe, persistent or unusual, speak to your prescriber rather than waiting them out.

How long it stays in the body

Tirzepatide has a half-life of about five days, so after a final dose it takes roughly four to five weeks to clear the system. There is no way to speed this up, and nothing needs doing while it clears.¹ This is useful to know if you are planning to stop treatment or if you are worried about a side effect after your last dose.

06 · Dose ladder

The dose ladder: why you start low and step up

Everyone starts Mounjaro on 2.5mg once a week, and the dose is then raised gradually. This starting dose is about letting your body adjust, not about weight loss itself. After at least 4 weeks the dose increases to 5mg, and can then step up by 2.5mg at a minimum of 4-week intervals (7.5mg, 10mg, 12.5mg) up to a maximum of 15mg weekly, depending on how you respond and tolerate it.¹

Many people settle at a maintenance dose of 5mg, 10mg or 15mg. Higher is not automatically better, and your prescriber will guide the right pace.¹ A person who responds well and tolerates 5mg may have no reason to climb further, while another may need a higher strength.

Wegovy follows a similar principle

The Wegovy pens are 0.25mg, 0.5mg, 1mg, 1.7mg and 2.4mg once weekly. Like Mounjaro, it starts low to improve tolerability.

What the pen contains

Each KwikPen contains four weekly doses, so one pen covers a month at a single strength.¹ If you step up after 4 weeks on each dose, your first four pens (2.5mg to 10mg) cost £959.96 at standard prices. A new customer's first order is £40 less, and every later order is £25 less.

What not to do

Altering doses outside the licence means unknown dosing accuracy and no safety data.¹ If side effects are bothering you, tell your prescriber instead of changing anything yourself.

07 · Using the pen

How to use a weekly injection pen

Mounjaro is injected under the skin (subcutaneously) once a week, on the same day each week, at any time of day, with or without food.¹ Licensed injection sites are the stomach area (at least 5cm from the belly button), the front of the thigh, or the back of the upper arm if someone else gives the injection. Rotate the site with each dose. Each KwikPen contains four weekly doses.¹³ Needles, a sharps bin and injection guidance are included with every order from us, and you should follow the pen's instructions each time.

Choosing a day and time

There is no "best" time of day. Mounjaro works the same morning or evening, with or without food. What matters is the same day each week. Pick a day and time you will remember. Many people choose a weekend morning so early side effects fall on days off, and then stick to it.¹ Our free GLPTrackr companion app can help you keep track of doses.

If you miss a dose

If you miss a dose, take it as soon as you can within 4 days (96 hours) of the scheduled time, then carry on with your usual day. If more than 4 days have passed, skip the missed dose entirely and take the next one on your normal day. Never take two doses within 3 days of each other.¹

Changing your injection day

You can change your weekly injection day if needed, as long as at least 3 days (72 hours) have passed since your last dose.¹ This is useful for holidays, shift changes or when you realise a weekday suits you better than a weekend. If you are unsure about timing after a missed or moved dose, contact the prescribing team before injecting.

Aftercare matters here. Our prescribing team provides ongoing monthly reviews, dose-titration and follow-up assessments, plus side-effect support, so you are not left to work things out alone. Repeat orders re-check suitability, and nothing ships automatically.

08 · Realistic results

What results can you realistically expect?

Weight loss on a weekly injection is gradual by design, so think in months, not days. The first weeks on 2.5mg are an adjustment phase and losses are usually modest; most measurable progress builds from 5mg onward, month by month. Trials measured results at 72 weeks, and you should judge progress by trend, not individual weigh-ins.¹²

The headline trial figures

In the SURMOUNT-1 trial of 2,539 adults, people taking tirzepatide alongside diet and exercise lost on average 15% of their body weight on 5mg, 19.5% on 10mg and 20.9% on 15mg over 72 weeks, compared with 3.1% with lifestyle changes alone. These are trial averages. Individual results vary, and treatment works alongside a reduced-calorie diet and increased physical activity, not instead of them.²

Those averages hide a wide spread. At 72 weeks, 85% of participants on 5mg, 89% on 10mg and 91% on 15mg had lost at least 5% of their body weight. Half of participants on 10mg and 57% on 15mg lost at least 20% of their body weight.² The trial average does not predict your own result.

What the early months look like

Three months in, most people are still on the lower rungs of the dose ladder, so trial-average losses at this stage are modest compared with the headline figures. A sensible 3-month expectation on a standard titration is mid single digits as a percentage of body weight, with wide individual variation. Slower early progress does not predict failure, because the dose you respond to may still be ahead of you.²

Some people notice appetite change and early loss in week one, while others feel little until a higher dose. Both are normal. Early loss includes water weight, so the trend over weeks matters more than any single weigh-in.¹ Our guide to average weekly weight loss on Mounjaro covers this pace question in more depth.

How a prescriber reviews progress

Treatment response is reviewed by your prescriber: if you have lost less than 5% of your starting weight after 6 months on the highest dose you can tolerate, your prescriber will discuss whether continuing or stopping is right for you.¹

Plateaus

Weight loss is not linear. Plateaus of a few weeks are normal and expected as the body adapts to a lower weight. Within the licence, review food intake honestly because portions drift back up, protect protein and activity, check the basics such as sleep and alcohol, and discuss with your prescriber whether a dose step-up is appropriate if you are not yet at maximum. A plateau is not a reason to double doses or add unlicensed products.¹

09 · Beyond the scales

Health changes beyond weight

Weight is only one outcome that prescribers look at. In trials, weight loss on tirzepatide came with average improvements in waist size, blood pressure, cholesterol and blood-sugar measures, and most participants with prediabetes returned to normal blood-sugar levels. These are trial-average secondary outcomes, not promises, but they are why prescribers talk about weight management as health management rather than appearance.²

Why this matters when you are deciding

Looking at blood pressure, cholesterol and blood sugar alongside the scales gives you a fuller picture of whether treatment is helping. Ask your prescriber or GP which measurements are worth tracking in your case.

Common mistakes when trying to lose weight

Whether or not you use medication, a few habits undermine progress. Relying on one number on the scales every day leads to frustration, because water weight moves constantly. Cutting food so far that you lose protein and energy makes activity harder to sustain. Treating the injection as the whole plan, rather than a support for changing your diet and movement, tends to leave people with nothing to fall back on if treatment stops. And chasing very fast loss in a short window is both unrealistic and unhelpful.

A more sustainable approach is to protect protein, stay active in ways you enjoy, keep sleep regular, watch alcohol, and review portions honestly as appetite changes. These are the same basics your prescriber will raise if progress slows.¹

Signs the medicine is working

There is no single reliable sign. Some people notice that they feel full sooner, think about food less between meals, or find portions smaller than before. Others see changes in how clothes fit before the scales move. None of these is a diagnostic test, and absence of them in the first weeks is not a failure. Judge progress by the trend over months, with your prescriber.

If you want to understand how this fits with type 2 diabetes care, see our guide to weekly injections for diabetes and weight loss, and speak to your own clinician about your situation.

10 · NHS and private

NHS or private: how do you get a weekly injection in the UK?

You can get a weekly weight loss injection through the NHS or through a regulated private pharmacy, and the right route depends on your eligibility and how long you are willing to wait. Mounjaro is available on the NHS, but access is being phased in over several years. NICE recommends it for adults with a BMI of at least 35 plus at least one weight-related condition, and the NHS primary-care rollout began in June 2025 with the highest-need groups first (initially BMI 40+ with four or more qualifying conditions).⁴⁶

Full rollout is expected to take years, which is why many people who meet the licensed criteria choose regulated private treatment rather than waiting. For Wegovy, NHS access runs through specialist weight-management services; ask your GP.

Talk to your GP first if you can

Your GP knows your history and can tell you whether you are likely to qualify for NHS treatment now or later. If you are already on other medicines, especially for diabetes, your GP or prescriber should know about them, because doses of some treatments may need adjusting. Never stop or change other medicines yourself.

How private treatment works with us

EverydayMeds is a GPhC-registered UK online pharmacy (registration 9012878), and you can check us on the public register. Our process is simple:

• Free online consultation. A short health questionnaire, no charge and no obligation.
• Prescriber review. Your answers are reviewed by a GPhC-registered prescriber, not a scoring script. Payment is taken when you place the order; if the prescriber decides the treatment is not suitable, the order is refunded automatically in full.
• Dispensing and dispatch. Dispensed by our registered pharmacy, with same-day dispatch when ordered by 3pm.
• Delivery. Free next-day tracked delivery in discreet, temperature-controlled packaging. Saturday delivery is £14.99.

Mounjaro comes through official LillyDirect supply, direct from Eli Lilly's UK distribution, as genuine KwikPens, and all six doses are in stock. The consultation is free, and the price shown is the price paid, with no hidden fees. You can pay by Visa or Mastercard, Klarna or pay-monthly options, and there are no subscriptions.

Avoiding counterfeit and unregulated sellers

Only buy from a registered pharmacy. Be wary of anyone offering to supply without a consultation or prescription, of social-media sellers, and of prices that look too good to be true. You can check a pharmacy on the GPhC register, and you can report suspected counterfeit medicines or side effects through the MHRA Yellow Card scheme.⁷¹⁹

11 · Storage and travel

Storing and travelling with your weekly pen

Keep Mounjaro pens in a fridge at 2–8°C and never freeze them. Once in use, a pen can be kept out of the fridge not above 30°C for up to 30 days, which is useful for short trips, after which it should be discarded. Keep the pen cap on to protect it from light, and never use a pen that has been frozen.¹¹³

Unopened pens

Unopened pens should be kept in the fridge and keep until the expiry date printed on the box. If an unopened pen has been out of the fridge, check with the pharmacy before using it rather than relying on a remembered day limit. Figures circulating online often come from other countries' labels, and they may not apply to a UK pen.¹³

Flying and holidays

You can fly with Mounjaro. Carry pens in hand luggage, because hold luggage can fall below freezing, ideally in a cool bag with the prescription label or a copy of your prescription. In-use pens tolerate up to 30 days not above 30°C, so most holidays need no special arrangements; for hot climates use an insulated pouch. Check destination rules for travelling with prescription injectables before you fly.¹³

Delivery and cold chain

Your order arrives by free next-day tracked delivery in temperature-controlled, discreet packaging. When it arrives, put pens that are not yet in use into the fridge. Keep your sharps bin somewhere safe and out of reach of children.

If something looks wrong

Do not use a pen that has been frozen, looks damaged or does not turn to a full dose. Contact us on 0333 207 0413 or at support@everydaymeds.co.uk, Monday to Friday, 9am to 5pm. If a dispensed item is faulty, damaged or wrong, contact us within 3 days. Dispensed prescription medicines cannot otherwise be returned.

12 · Safety and side effects

Safety, side effects and what to avoid

The commonest early effects of a weekly injection are mild and usually settle. Mild nausea, altered appetite and tiredness in the first days after each injection are the commonest early effects and usually settle.¹ The starting weeks on 2.5mg are about adjustment, and experiences differ widely between people.

When to speak to a prescriber

Speak to your prescriber if symptoms are severe, do not settle or feel unusual for you, and before you change any dose. You can also report any suspected side effect through the MHRA Yellow Card scheme.¹⁹ Tell your prescriber about any new or lasting symptom.

Other medicines and contraception

Tell your prescriber about everything you take. If you take insulin or sulfonylureas, doses may need adjusting because of the risk of low blood sugar. The medicine can also reduce absorption of oral contraceptives because stomach emptying slows.⁷ The SmPC advises switching to a non-oral method, or adding a barrier method (such as condoms), for 4 weeks after starting Mounjaro and for 4 weeks after each dose increase.¹

Things not to do

• Do not alter doses outside the licence, including smaller, stretched or extra doses.
• Do not take two doses within 3 days of each other.
• Do not add unlicensed products to "boost" results.
• Do not buy from sellers who offer to supply without a consultation or prescription.

A plateau is not a reason to double doses or add unlicensed products.¹ Instead, review food intake, protect protein and activity, check sleep and alcohol, and ask your prescriber whether a step-up is appropriate.

A note on mental health

The EMA's safety committee reviewed the evidence and concluded in 2024 that it does not support a causal link between GLP-1 medicines and suicidal thoughts, and the MHRA keeps this under continuous review.¹⁷ Any big change in weight, appetite and routine can affect how you feel: tell your prescriber about any history of depression, and seek help promptly if your mood drops or you have distressing thoughts during treatment.

If you have thoughts of harming yourself or ending your life, get help straight away. Call 999 or go to A&E if you are in immediate danger. In England you can call NHS 111 and choose the mental health option, any time. You can also call Samaritans free on 116 123, day or night. Tell your prescriber about any change in your mood while taking Mounjaro.

Mounjaro is a prescription-only medicine. This page is information, not a substitute for medical advice.

13 · Costs over time

What does a weekly injection cost over time?

Standard prices per pen, which covers four weekly doses, are £169.99 at 2.5mg, £218.99 at 5mg, £279.99 at 7.5mg, £290.99 at 10mg, £319.99 at 12.5mg and £329.99 at 15mg. These were checked 10 October 2026, and you can see live prices on the Mounjaro product page.

All figures are at standard prices, before discounts. New customers save £40 on their first order with code FIRST40, and an automatic £25 reorder discount applies to every future order (code DOSE25). If you switch to us at a higher dose, the first-order discount still applies. For example, a first 15mg pen is £289.99 as a first-order price.

Comparing with other pharmacies

Across the UK pharmacies we track, Mounjaro pens ranged from £143.96 to £339.00 per month across all doses as of 10 October 2026. Starting pens ranged from £143.96 to £179.99. The gap between providers for the same dose was between £27 and £41. Boots' Mounjaro dose prices ranged from £179.00 to £339.00 per month. Compare like for like by dose, and remember that a low price means nothing if the supplier is not registered.

Payment is flexible: Visa, Mastercard, Klarna and pay-monthly options, with no subscription lock-in. You choose each order, and repeat orders re-check suitability. If you want a plain tour of the options, our weight loss clinic page is the place to start.

14 · Serious side effects

Serious side effects: when to get help straight away

Serious side effects are uncommon but need urgent attention. Seek immediate medical help for: severe, persistent stomach pain that may spread to your back, with or without vomiting (possible pancreatitis); pain in the upper right abdomen, fever or yellowing of skin/eyes (possible gallbladder problems); or signs of a severe allergic reaction such as swelling of the face or throat and difficulty breathing. If you take insulin or a sulfonylurea alongside Mounjaro, watch for low blood sugar (shakiness, sweating, confusion) — your prescriber may need to adjust those medicines.¹