Weight Loss Jabs Guide UK (October 2026)

01 · Choosing

Which weight loss jab should I take?

The right jab is the one a prescriber judges suitable for your BMI, medical history and current medicines, so no single jab suits everyone. Three names come up most often in the UK: Mounjaro, Wegovy and Saxenda.

Mounjaro is the only one of these that targets two receptors at once, which distinguishes it from single-action medicines such as semaglutide.¹ That is a difference in mechanism, not a promise that it will work better for you. A weekly jab is also easier to fit around life than a daily one for many people. If you are weighing Wegovy against Mounjaro, a prescriber can talk through tolerability and your medical history. You can also read our wider overview of weight loss injections or see all weight loss treatments.

Not every treatment is an injection either. Orlistat, for example, is a capsule with its own dosing rules, covered in our orlistat dose guide.

02 · Cost

What does a weight loss jab cost?

The standard price of one Mounjaro pen (four weekly doses, 4 weeks) is £169.99 at 2.5mg, £189.99 at 5mg, £244.99 at 7.5mg, £274.99 at 10mg, £289.99 at 12.5mg and £299.99 at 15mg. You can see live prices and consultation details on the Mounjaro pen page, and all six doses are in stock.

New customers get £40 off their first order at any dose with code FIRST40. That makes your first 2.5mg pen £129.99 (standard price £169.99). Switching to us at 15mg? Your first order is £259.99. After that, an automatic £25 reorder discount applies to every future order (code DOSE25), so every later order is £25 off the standard price.

For planning, if you step up after 4 weeks on each dose, your first four pens (2.5mg to 10mg) cost £879.96 at standard prices. A first year of 13 pens costs £2,399.88 if you settle at 5mg, up to £3,279.88 at 15mg. These totals are before discounts, so a new customer's first order is £40 less and every later order £25 less. If you settle at another dose, use that dose's monthly price rather than a year figure.

Our consultation is free, and the price shown is the price paid, with no hidden fees. Payment is by Visa, Mastercard or Klarna, with pay-monthly options and no subscriptions.

03 · NHS or private

NHS or private: the honest picture

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 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. If you are unsure where you fit, ask your GP. NHS access to Wegovy runs through specialist weight-management services, so ask your GP about that too.

Choosing private care means a GPhC-registered prescriber reviews your consultation, and our pharmacy is registered with the GPhC (9012878). Our Mounjaro comes via official LillyDirect supply, direct from Eli Lilly's UK distribution. Delivery is free, next-day, tracked and temperature-controlled, with same-day dispatch when ordered by 3pm. Saturday delivery is £14.99.

04 · Ordering

How ordering works

• Free online consultation: a short health questionnaire, no charge and no obligation. Start your free consultation.
• Prescriber review: a GPhC-registered prescriber reviews it. 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 delivery: our registered pharmacy dispenses, and free next-day tracked delivery follows. Needles, a sharps bin and injection guidance come with every order.

You can also read how registering for weight loss injections online works step by step.

05 · How the jabs work

How weight loss jabs work

Mounjaro contains tirzepatide, which activates two natural gut-hormone receptors at once: GIP and GLP-1. Together these help regulate appetite, slow how quickly the stomach empties and improve how the body responds to insulin.¹ In practice, most people feel fuller sooner and less hungry between meals, which supports a reduced-calorie diet.

That last part matters. The jab is not a substitute for eating less and moving more. It is licensed for use alongside a reduced-calorie diet and increased physical activity.¹ Mounjaro is made by Eli Lilly, comes as a pre-filled multi-dose KwikPen and is licensed in the UK for weight management in adults and for type 2 diabetes.

Tirzepatide has a half-life of about five days, so after a final dose it takes roughly 4–5 weeks to clear the system. There is no way to speed this up, and nothing needs doing while it clears.¹

06 · Who can have one

Who can have a weight loss jab?

Mounjaro is licensed for adults with a BMI of 30 or above, or a BMI between 27 and 30 with at least one weight-related condition. Examples include high blood pressure, high cholesterol, obstructive sleep apnoea, cardiovascular disease, prediabetes or type 2 diabetes.¹¹¹ It must be used with a reduced-calorie diet and more physical activity.

A prescriber assesses your BMI, medical history and current medicines before deciding whether it is suitable. Our guide to BMI and eligibility for weight loss injections goes into more detail. If you have a thyroid condition, see our guide to weight loss injections and thyroid problems, and always tell the prescriber about it.

07 · Dosing and first weeks

Dosing and what to expect in the first weeks

Everyone starts Mounjaro on 2.5mg once a week, and this starting dose is about letting your body adjust, not about weight loss itself. After at least 4 weeks the dose increases to 5mg. It can then step up by 2.5mg at a minimum of 4-week intervals (7.5mg, 10mg, 12.5mg) to a maximum of 15mg weekly, depending on how you respond and tolerate it.¹ Many people settle at 5mg, 10mg or 15mg. Higher is not automatically better, and your prescriber guides the pace.

What to expect in week 3? You are still on the 2.5mg starting dose, because the first increase comes after at least 4 weeks. Experiences differ widely. Some people notice appetite change and early loss in week one, while others feel little until a higher dose, and both are normal. Early loss includes water weight, so the trend over weeks matters more than any single weigh-in. Mild nausea, altered appetite and tiredness in the first days after each injection are the commonest early effects and usually settle.¹³ Our Mounjaro side effects guide covers these in detail.

08 · How to inject

How to inject, and the best time of day

Mounjaro is injected under the skin once a week, on the same day each week, at any time of day, with or without food. Licensed 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.¹ Each KwikPen contains four weekly doses.

There is no "best" time of day, because Mounjaro works the same morning or evening. What matters is the same day each week. Many people choose a weekend morning so early side effects fall on days off.¹³

If you miss a dose, take it as soon as you can within 4 days (96 hours) of the scheduled time. If more than 4 days have passed, skip it and take the next one on your normal day. Never take two doses within 3 days of each other. You can change your injection day as long as at least 3 days (72 hours) have passed since your last dose.¹

09 · Realistic results

What results look like

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.² These are trial averages and individual results vary. For someone starting at 100 kg, 20.9% is about 21 kg.

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%.² Trial averages do not predict your own result.

Weight loss on Mounjaro is gradual by design. The first weeks on 2.5mg are an adjustment phase, and most measurable progress builds from 5mg onward, month by month. Think in months, not days, and judge progress by trend rather than single weigh-ins. Your prescriber reviews your response: if you have lost less than 5% of your starting weight after 6 months on the highest dose you can tolerate, they will discuss whether continuing or stopping is right for you.¹

10 · Food, alcohol, medicines

What to avoid: food, alcohol and other medicines

No food is banned on Mounjaro, including bananas. Prioritise protein at each meal, vegetables and fibre, and regular fluids. Many people feel worse after very fatty, fried or very sugary food, and smaller, slower meals work better. There is no direct interaction between Mounjaro and alcohol, but drinking on a reduced appetite and emptier stomach can hit harder than usual. If you also take insulin or a sulfonylurea, alcohol increases the risk of low blood sugar.

On other medicines, Mounjaro slows stomach emptying, which can reduce how well oral contraceptive pills are absorbed.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 If you take insulin or sulfonylureas, doses may need adjusting because of the risk of low blood sugar. These are not "never combine" rules. Tell your prescriber about every medicine you take, including over-the-counter products and supplements.

On long-term effects, ongoing monthly reviews let the prescribing team monitor how you are doing. If you notice a new symptom, discuss it with your prescriber and report suspected side effects through the Yellow Card scheme.¹⁹

11 · Storage and travel

Storage, holidays and travelling

Keep 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 cap on to protect it from light, and never use a pen that has been frozen.¹

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. Most holidays need no special arrangements, but for hot climates use an insulated pouch, and check destination rules for prescription injectables before you fly.¹³ Unopened pens stay in the fridge and keep until the expiry date on the box. If an unopened pen has been out of the fridge, check with the pharmacy before using it.

12 · Spotting a genuine pen

How to check a pen is genuine

A genuine UK Mounjaro pen comes from a registered pharmacy with a batch number and expiry date, arrives cold-chain packaged, and the solution inside is clear and colourless.¹³ Do not use a pen that has been frozen, looks cloudy or discoloured, has particles, is past its expiry, or has been out of the fridge for more than 30 days, or above 30°C in use.

Be wary of anyone offering to supply without a consultation or prescription. If supply or packaging ever seems wrong, check the pharmacy on the GPhC register and contact it before injecting.¹² You can report counterfeit concerns through the MHRA.⁷ Mounjaro is a prescription-only medicine, supplied only after an online consultation reviewed by a GPhC-registered prescriber, and this page is information rather than a substitute for medical advice.

13 · 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