Cheapest Injectable for Weight Loss in the UK (October 2026)

01 · Cost

What the cheapest weight loss injection really costs

The lowest sticker price is not always the lowest cost. A weight loss injection is a monthly commitment that usually runs for many months, and the price changes as the dose rises. Looking only at the first pen can mislead you, because most people do not stay on the starting dose.

For Mounjaro, your first 2.5mg pen costs £129.99 with code FIRST40 (standard price £169.99). A new customer gets £40 off their first order at any dose, including people switching to us at a higher strength. Switching at 15mg? Your first order is £289.99. After that, every later order is £25 off the standard price (code DOSE25). You can read how the codes work in our Mounjaro discount code guide.

Across the UK pharmacies we track (checked 11 October 2026), the cheapest and dearest Mounjaro 2.5mg starting pens run from £143.96 to £179.99. Across all doses and providers the range is £143.96 to £339.00. For the same dose, the gap between providers is anywhere from £27 to £41. Boots' own Mounjaro dose prices run from £179.00 to £339.00. If you want a fuller breakdown of the tirzepatide market, see our tirzepatide price comparison.

02 · Comparison

Weight loss injectables compared on cost and frequency

There are three kinds of injectable weight loss treatment people ask about in the UK.

A cheaper first pen is not the same as a cheaper treatment. The right question is what you will pay each month at the dose you are likely to stay on, and for how long. Our injectable weight loss medication list goes deeper on each option.

03 · What you pay for

What the price includes, and how ordering works

The price shown is the price paid. The consultation is free, and delivery is free and next-day: tracked DPD in temperature-controlled, discreet packaging. Saturday delivery is £14.99. Needles, a sharps bin and injection guidance come with every order, and our Mounjaro is supplied through official LillyDirect supply, direct from Eli Lilly's UK distribution. All six doses are in stock, and there are no subscriptions, so you only pay when you reorder.

Ordering takes three steps:

• Free online consultation. Complete a short health questionnaire. There is no charge and no obligation. Start your free consultation.
• Prescriber review. A GPhC-registered prescriber reviews your answers. 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 your order, with same-day dispatch when ordered by 3pm, then free next-day tracked delivery.

You can pay by Visa, Mastercard or Klarna, and pay-monthly options are available. Repeat orders re-check suitability, and nothing is shipped automatically.

04 · What Mounjaro is

What Mounjaro is and why it dominates the price conversation

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.¹ It comes as a pre-filled multi-dose pen, the KwikPen, in six strengths: 2.5mg, 5mg, 7.5mg, 10mg, 12.5mg and 15mg. Each pen contains four weekly doses, so one pen covers four weeks.¹³

That four-week pen is why prices are quoted per month. When you compare injections, it helps to translate everything to the same unit: what you pay for four weeks of treatment at the dose you are actually taking. Our weekly equivalents run from £42.50 per week at 2.5mg to £82.50 per week at 15mg, at standard prices before any discount.

The brand decides how often you inject. The dose decides your monthly price. The provider decides whether you can trust what arrives. A low price on the wrong dose, or from a supplier you cannot check, is not a saving.

Because Mounjaro is a prescription-only medicine, no legitimate seller can offer it without a consultation. Anyone offering to supply without a consultation or prescription is not operating within UK rules, whatever the price. Our own supply is through Lilly's official distribution to licensed pharmacies, and each pen carries a batch number and expiry date that can be checked.¹

If you are weighing up several treatments rather than Mounjaro alone, our overview of weight loss injectable drugs sets out the main options side by side, and our all weight loss treatments page covers the wider range we offer. Mounjaro (tirzepatide) is a prescription-only medicine, supplied only after an online consultation reviewed by a GPhC-registered prescriber. It is used alongside a reduced-calorie diet and increased physical activity. Individual results vary, and this page is information, not a substitute for medical advice.

05 · How it works

How tirzepatide works, and why that matters for value

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.

This dual action is what distinguishes Mounjaro from single-action GLP-1 medicines such as semaglutide (Wegovy and Ozempic).¹ That is a difference in how the medicines work, not a verdict on which one is right for you. Both are licensed treatments, and a prescriber decides which suits your health and your circumstances.

Why does mechanism belong on a price page? Because value is not only about cost per month. When you compare, look at practical fit as well as price: weekly versus daily injecting, how you handle early side effects, and what dose you are likely to settle on.

One more mechanism detail affects planning. Tirzepatide has a half-life of about five days, so after a final dose it takes roughly 4 to 5 weeks to clear the system. There is no way to speed this up, and nothing needs doing while it clears.¹ Stopping does not take effect overnight, and stopping should always be planned with your prescriber, with diet and activity habits ready to carry the load.

Because the slowed stomach emptying can also reduce how well oral contraceptive pills are absorbed, tell your prescriber what you take. 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 This is covered in your consultation. The same applies to anyone on insulin or sulfonylureas, where doses may need adjusting because of the risk of low blood sugar.

06 · Cost over a year

What a year of Mounjaro costs at different doses

A realistic year-cost estimate matters more than the first-pen price. Mounjaro starts at 2.5mg for everyone, then steps up, so your monthly cost changes as you move through the doses.

A new customer's first order is £40 less than the standard price, and every later order is £25 less. These totals do not subtract those savings, so your own spend will be lower.

If you settle somewhere in between, work from the monthly price of that dose: £279.99 at 7.5mg, £290.99 at 10mg and £319.99 at 12.5mg, again at standard prices.

Three practical points follow. Higher is not automatically better, and your prescriber will guide the pace. Second, comparing providers at the same dose is the fairest test, because one provider's cheap 2.5mg pen may sit alongside a much dearer 15mg pen. Third, you can spread cost with Klarna or pay-monthly options, and there is no subscription to cancel.

When you compare quotes, add up the whole route: the starting pens, the doses you will probably move through, delivery and any consultation fee. Our consultation is free and delivery is free next-day tracked, so the pen price is the whole price. The price shown is the price paid.

07 · Dose ladder and cost

The dose ladder: why monthly cost rises over time

Everyone starts Mounjaro on 2.5mg once a week. This starting dose is about letting your body adjust, not about weight loss itself.¹ After at least 4 weeks the dose increases to 5mg, and it 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

Each KwikPen is designed and licensed to deliver exactly four weekly doses, so a pen is a four-week supply at whatever strength you are on.¹³ The pen is set by turning the dose knob until the dose indicator shows the right number in the window.

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 Our ongoing monthly clinical reviews, dose titration and follow-up assessments are part of the service. For more on the prescribing side, see our guide to weight loss injectable medication.

08 · NHS versus private

NHS versus private: the honest cost picture

Mounjaro is available on the NHS, but access is being phased in over several years.⁵ NICE recommends it for adults with a BMI of at least 35 plus at least one weight-related condition. 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.

On cost alone, an NHS prescription is the lowest-cost route if you qualify and can access it. In England the standard prescription charge is £9.90 per item, though exemptions apply. The practical question is whether you fall within the groups being treated yet, and how long you may wait. This is why many people who meet the licensed criteria choose regulated private treatment rather than waiting.

Private treatment is not the same as unregulated treatment. A regulated pharmacy still requires a prescription and a clinical consultation, reviewed by a GPhC-registered prescriber. That is the line between a legitimate private supply and the grey market, and it holds regardless of price.

Licensed eligibility for private prescribing is wider than the NHS rollout criteria. Mounjaro is licensed for weight management in 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.¹ It must be used alongside a reduced-calorie diet and increased physical activity. A prescriber will assess your BMI, medical history and current medicines before deciding whether it is suitable for you.

A sensible approach is to ask your GP about NHS access first, particularly if you are in a higher-need group, and to keep a regulated private route in mind if the wait is not suitable for you. Wegovy's NHS access runs through specialist weight-management services, so ask your GP about that too.

09 · Results to expect

What you get for the money: trial results and realistic pace

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. Treatment works alongside a reduced-calorie diet and increased physical activity, not instead of them.

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 As a worked example only, for someone starting at 100 kg, 20.9% is about 21 kg. Trial averages do not predict your own result.

These results help when you judge value. Your prescriber matches the dose to your response and tolerance, and that, rather than the price list, should drive the decision.

The pace is gradual by design. 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, so think in months, not days, and judge progress by trend, not individual weigh-ins.¹

Experiences in the first weeks 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. Mild nausea, altered appetite and tiredness in the first days after each injection are the commonest early effects and usually settle.¹

For cost planning, this means budgeting for several months of treatment rather than a single pen.

10 · Counterfeit risk

Why the very cheapest pen can be the most expensive mistake

The MHRA has seized thousands of fake weight-loss pens in the UK and has issued alerts after falsified Mounjaro pens were identified. Fake pens have caused hospitalisations, and some contained insulin rather than tirzepatide.⁷ Only buy from a pharmacy you can verify on the GPhC register, never from social media, beauty salons or unverified websites.¹² Genuine treatment always involves a prescription and a clinical consultation.

That is why a price that looks too good to be true should make you stop. A real saving comes from a verified pharmacy using a transparent discount. A suspicious one comes from a seller who will not ask about your health, and no price is worth that risk. You can check our registration (GPhC 9012878) on the public register.

Genuine stock is supplied through Lilly's official distribution to licensed pharmacies, and every pen carries a batch number and expiry date that can be checked.¹ A genuine UK Mounjaro pen comes from a registered pharmacy, arrives cold-chain packaged, and the solution inside is clear and colourless.

Do not use a pen if it:

• has been frozen;
• looks cloudy or discoloured;
• has particles in it;
• is past its expiry;
• has been out of the fridge for more than 30 days in use, or above 30°C.

If supply or packaging ever seems wrong, check the pharmacy on the GPhC register and contact the pharmacy before injecting.¹³

If you ever experience a side effect, or suspect a product is not genuine, you can report it through the MHRA Yellow Card scheme.¹⁹ Reporting helps regulators spot problems with falsified products quickly.

A few simple habits protect you: buy only from a pharmacy that insists on a consultation, keep the box and batch number, and register concerns early. Our own service reviews every order through a GPhC-registered prescriber before dispensing, and an unsuitable order is refunded automatically in full.

11 · Weekly vs daily injections

Weekly or daily: how Mounjaro, Wegovy and liraglutide differ

The three injectables people compare differ first in how often you inject. Mounjaro and Wegovy are both once-weekly injections. Liraglutide, supplied as Saxenda or products such as Erly, is a daily injection at a concentration of 6mg per millilitre. Daily dosing means more injections each month, and that may matter more to you than a small difference in price.

Wegovy (semaglutide) comes in pens of 0.25mg, 0.5mg, 1mg, 1.7mg and 2.4mg once weekly. It steps up after at least 4 weeks, reaching the 2.4mg maintenance dose from week 17, and 2.4mg is the licensed maintenance dose for weight management.¹⁸ Its first pen costs £99.99 as a first-order price.

Mounjaro (tirzepatide) has six strengths from 2.5mg to 15mg, with at least 4 weeks between steps, and activates both GIP and GLP-1 receptors, while semaglutide is a single-action GLP-1 medicine.¹

Choosing by price alone can leave you on a daily injection you dislike, or a dose ladder that suits you less. A prescriber can help you weigh price against tolerability and practicality.

12 · Using and storing pens

Using and storing your pen so none of it is wasted

A pen you store or use badly is money lost, so a few practical rules protect your spend. 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.¹³

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

Keep pens in a fridge at 2 to 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.¹³ Unopened pens stay in the fridge and keep until the printed expiry date. If an unopened pen has been out of the fridge, check with the pharmacy before using it.

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 if at least 3 days (72 hours) have passed since your last dose.¹³

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 check destination rules for prescription injectables before you fly.¹³

Existing customers can manage reorders and reviews through the injectable account login. Our support team is on 0333 207 0413 or support@everydaymeds.co.uk, Monday to Friday, 9am to 5pm. Our free GLPTrackr app helps you track your journey on iOS and Android.

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