Mounjaro Weight Loss Injection Info: How It Works, Results and Cost (October 2026)

01 · Cost and access

What Mounjaro costs and how to get it in the UK

Mounjaro is a prescription-only medicine, so you cannot simply buy it: a GPhC-registered prescriber has to review your suitability first. The Mounjaro pen comes in six strengths, and the starting 2.5mg pen costs £169.99 for four weekly doses. All six doses are in stock. A new customer saves £40 on their first order, at any dose, with code FIRST40. An automatic £25 reorder discount applies to every future order (code DOSE25).

Because the discount applies to a first order at any dose, people switching to us from another provider at a higher dose benefit too. Every later order is £25 off the standard price of the dose you are on. The consultation is free, and the price shown is the price paid, with no hidden fees. Needles, a sharps bin and injection guidance come with every order.

02 · Planning

What a first year of Mounjaro costs

The dose ladder means your cost changes as you move up. These figures use standard prices before any discount. A new customer's first order is £40 less, and every later order is £25 less.

Higher is not automatically better. Many people settle at 5mg, 10mg or 15mg, and your prescriber guides the pace, so your own total may sit anywhere in that range.¹

Across the UK pharmacies we track, a Mounjaro pen at any dose ranges from £143.96 to £319.99 (checked 24 October 2026). Starting 2.5mg pens range from £143.96 to £179.99. For the same dose, the gap between providers runs from £20 to £36.03. Compare like for like, dose by dose, and check that the seller supplies genuine pens.

03 · NHS vs 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. The NHS primary-care rollout began in June 2025 with the highest-need groups first, initially BMI 40 or above with four or more qualifying conditions.⁴⁶ Full rollout is expected to take years. That is why many people who meet the licensed criteria choose regulated private treatment rather than waiting.

If you go private, choose a pharmacy you can verify. Ours is registered with the GPhC (9012878), and Mounjaro comes through official LillyDirect supply, direct from Eli Lilly's UK distribution, as genuine KwikPens.¹² Be wary of anyone offering to supply without a consultation or prescription, and report suspect products or side effects through the Yellow Card scheme.⁷ Our guide to weight loss injection claims explains the common red flags.

04 · Ordering

How ordering works in three steps

First, complete the free online consultation, a short health questionnaire with no charge and no obligation. Second, 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. Third, our registered pharmacy dispenses and ships. Orders placed by 3pm are dispatched the same day, with free next-day tracked DPD delivery in discreet, temperature-controlled packaging. Saturday delivery is £14.99.

Payment is by Visa, Mastercard or Klarna, with pay-monthly options and no subscriptions. Repeat orders re-check suitability, and nothing ships automatically. Monthly reviews, dose-titration support and side-effect help from the prescribing team are included. Support runs Monday to Friday, 9am to 5pm, on 0333 207 0413. If you are weighing larger purchases, read whether you can bulk buy Mounjaro.

05 · What Mounjaro is

What Mounjaro is and what the active ingredient does

The active ingredient in Mounjaro is tirzepatide. Mounjaro is simply the brand name, and the medicine is made by Eli Lilly. It is a once-weekly injectable prescription medicine, and in the UK it is licensed for weight management in adults and for type 2 diabetes.¹ If you have seen "Mounjaro" and "tirzepatide" used as though they were different products, they are the same medicine under two names.

The medicine comes as a pre-filled, multi-dose pen called a KwikPen. There are six strengths: 2.5mg, 5mg, 7.5mg, 10mg, 12.5mg and 15mg. Each pen contains four weekly doses, so one pen covers four weeks. You dial the dose in the pen's window rather than drawing anything up yourself, which keeps the process simple for people who have never injected before.¹³

How it works

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. That supports a reduced-calorie diet, which is the part that produces weight loss. The medicine is a tool for eating less comfortably, not a replacement for changing how you eat and move.

This dual action is what distinguishes Mounjaro from single-action GLP-1 medicines such as semaglutide (Wegovy and Ozempic). That is a difference in mechanism, and it does not on its own tell you which medicine suits you. Both are licensed treatments, and a prescriber considers your history, preferences and tolerance when choosing.

How long it stays in the body

Tirzepatide has a half-life of about five days. 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. This is also why the weekly schedule works: a single injection keeps the medicine active across the whole week, and why the day of the week matters more than the hour of the day.

Who makes it and how it reaches you

Because Mounjaro is a prescription-only medicine, it can only be supplied after an online consultation reviewed by a GPhC-registered prescriber. Our supply comes through official LillyDirect channels, meaning direct from Eli Lilly's UK distribution. That matters because counterfeit and unregulated tirzepatide products circulate online. A genuine KwikPen arrives labelled with your prescription details, and we dispense it from our registered pharmacy. If you are ever unsure whether a pen is genuine, contact the pharmacy before using it.

Mounjaro (tirzepatide) is used alongside a reduced-calorie diet and increased physical activity. Individual results vary. This page is information, not a substitute for medical advice.

06 · Trial results

What the SURMOUNT-1 trial showed about weight loss

Yes, Mounjaro injections help people lose weight, and the clearest evidence comes from SURMOUNT-1. In that 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. People using lifestyle changes alone lost 3.1%.²

These are trial averages, and individual results vary. Treatment works alongside a reduced-calorie diet and increased physical activity, not instead of them. Trial averages do not predict your own result, so treat them as the likely range of outcomes rather than a target you must hit.

What the percentages mean in kilograms

Percentages are easier to picture as a worked example. For someone starting at 100 kg, 15% is about 15 kg, 19.5% is about 19.5 kg and 20.9% is about 21 kg. Someone starting at a different weight would see proportionally different numbers. These figures describe the average at 72 weeks, not a speed, and they do not tell you how much you will lose in any particular month.

How many people reached key thresholds

The trial also reported how many people reached specific milestones. 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 Reading those two sets of numbers together shows that most people on any of the tested doses lost a meaningful amount, while the larger losses were more common at higher doses.

Reading the results honestly

Three cautions apply. First, a trial average hides a spread: some people lose more and some less. Second, the figures belong to people who stayed in a structured programme with dietary advice, so your day-to-day habits still matter. Third, higher is not automatically better.

Do not set results from different trials side by side as though they were a head-to-head contest. They enrolled different people under different conditions. Where you want to compare Mounjaro with another medicine, ask your prescriber, who can place the evidence in the context of your health.

If you want to see how loss tends to unfold over time, our page on the Mounjaro weight loss curve explores the shape of progress. The key point from the trial is simple: the measured outcome was at 72 weeks, which is well over a year, so the sensible mindset is a long-term treatment plan rather than a quick fix.

07 · Pace of results

How quickly Mounjaro works and what to expect in three months

Mounjaro works gradually by design, so the honest answer to "how quickly" is months rather than 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.² 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.

The first weeks

Experiences in the starting weeks differ widely. Some people notice an 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 several weeks matters more than any single weigh-in. The commonest early effects are mild nausea, altered appetite and tiredness in the first days after each injection, and these usually settle.

Many people choose a weekend morning for their injection so that early side effects fall on days off. There is no medical need to do so, but it can make the first few weeks easier to manage.

Judge by trend, not single weigh-ins

Body weight moves up and down from day to day because of fluid, food in the gut and hormones. If you weigh yourself daily, the number will bounce, and that bounce can feel discouraging when the underlying direction is fine. A weekly weigh-in at the same time of day, or a rolling average, gives a clearer picture. The free GLPTrackr companion app (iOS and Android) lets you log your journey and see the trend rather than individual readings.

The 6-month review point

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.² That is not a pass-or-fail test of effort. It is a check that the medicine is doing enough to justify continuing.

What helps and what does not

The medicine reduces hunger and helps you feel full, but you still decide what and how much you eat. People who use the reduced appetite to build regular meals, enough protein and daily movement are working with the treatment as licensed. Sudden crash dieting is not part of the plan, and neither is chasing a faster pace by changing doses yourself. Our ongoing monthly reviews exist to keep progress steady and safe, and the prescribing team can answer questions between orders.

If progress feels slow, speak to the prescriber rather than adjusting anything alone. A held dose, a slower step up or a check on side effects is usually the sensible next move, and all of those sit within the licence.

08 · Who can use it

Who can use Mounjaro for weight loss

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.¹ Qualifying conditions include high blood pressure, high cholesterol, obstructive sleep apnoea, cardiovascular disease, prediabetes and type 2 diabetes. It must be used alongside a reduced-calorie diet and increased physical activity. That is the licence, and it is the basis a private prescriber works from.

What the prescriber assesses

Meeting a BMI threshold is necessary but not enough. A prescriber assesses your BMI, medical history and current medicines before deciding whether Mounjaro is suitable. That is why our consultation is reviewed by a GPhC-registered prescriber rather than 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. Being honest on the questionnaire is the single most useful thing you can do, because it lets the prescriber protect you.

Working out where you sit

BMI is your weight in kilograms divided by your height in metres squared. If the result is 30 or above, you fall in the first licensed group. If it is between 27 and 30, you need at least one weight-related condition from the list, such as prediabetes or high blood pressure. If your BMI is under 27, Mounjaro is not licensed for weight management for you. Our consultation is free and carries no obligation, so there is no cost to finding out where you stand.

Who the NHS prioritises

NHS criteria are tighter than the licence because supply is phased. NICE recommends tirzepatide for adults with a BMI of at least 35 plus at least one weight-related condition, and the first NHS groups are those with the highest need.⁴ You can meet the licensed criteria without yet qualifying for NHS prescribing, which is why the private route exists alongside it.

Questions to raise with a prescriber

• All the medicines and supplements you currently take, including any for diabetes.
• Any history of digestive problems or other long-term conditions.
• Whether you are pregnant, planning a pregnancy or breastfeeding. Mounjaro must not be used during pregnancy, and it should be stopped at least one month before trying to conceive. If you become pregnant during treatment, stop the medicine and tell your prescriber promptly.
• Your previous attempts at weight loss and what you want from treatment.

For people with type 2 diabetes who take insulin or sulfonylureas, doses may need adjusting because of the risk of low blood sugar. This is something the prescriber will discuss with you. It does not mean Mounjaro is ruled out. For a broader view of the options, our hub on weight loss injections compares the main routes.

09 · Dose ladder

The Mounjaro dose ladder and titration

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. 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.

Why the steps are gradual

The ladder exists for tolerability. A low start lets your digestive system get used to the medicine before the dose rises. The 4-week minimum is a floor, not a schedule, so your prescriber may hold you on a dose for longer if you are having side effects or if you are already getting the response you want. Slowing down is within the licence. Speeding up beyond it is not.

Six strengths, one pen each

Each KwikPen holds four weekly doses of a single strength. Moving up the ladder therefore means moving to a new pen, and our Mounjaro pen page shows all six strengths with live prices. Repeat orders re-check suitability, so each step is reviewed rather than shipped automatically.

Where people settle

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. The trial data showed benefit across 5mg, 10mg and 15mg, so a lower maintenance dose that you tolerate and respond to is a perfectly reasonable endpoint.²

What a typical early route looks like

• 2.5mg for at least 4 weeks, an adjustment phase.
• 5mg after at least 4 weeks, where measurable progress usually starts to build.
• Later steps: 7.5mg, 10mg and 12.5mg at no less than 4-week intervals, only if needed.
• Maximum: 15mg weekly.

That is only the path through the ladder, not a requirement to reach any particular dose. You stop climbing when you reach a dose that works for you.

What not to do

Altering doses outside the licence means unknown dosing accuracy and no safety data.

10 · How to inject

How to inject Mounjaro, and what to do if you miss a dose

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.¹³ Each KwikPen contains four weekly doses. Every order includes needles, a sharps bin and injection guidance, and the pen's own instructions walk you through each step.

Where to inject

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 rather than returning to the same spot, which helps the skin stay comfortable between injections.

Setting the dose

The KwikPen is set by turning the dose knob until the indicator shows the correct dose in the window. Follow the pen's instructions for how to deliver the injection.

Choosing a time of day

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, and stick to it. Many people choose a weekend morning so that early side effects fall on days off.

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 Skipping is safer than doubling up, so do not try to make up for it later.

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. This is helpful if your routine changes, for example a new shift pattern or a holiday. Move the day once, then keep to the new one.

A simple routine

• Take the pen out of the fridge following the leaflet's guidance, and check the label and dose window.
• Choose and clean the site, then rotate from the last one.
• Inject, following the pen's instructions, and dispose of the needle in the sharps bin.
• Log the dose, for instance in the GLPTrackr app, so you always know when the next one is due.

If anything about the pen looks wrong, such as a damaged pen or a window that will not turn, contact the pharmacy rather than improvising. Faulty, damaged or wrong items should be reported to us within 3 days of delivery.

11 · Storage and travel

Storing Mounjaro and travelling with it

Keep Mounjaro pens in a fridge at 2 to 8°C and never freeze them.¹ 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.

Unopened pens

Unopened pens should be kept in the fridge, and they 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 the UK leaflet is the reference to use.¹³

When your parcel arrives

Our deliveries arrive by free next-day tracked DPD in discreet, temperature-controlled packaging. Open the parcel promptly and put the pens in the fridge. If you will not be home, arrange for someone to receive it or choose a delivery option that suits you, including Saturday delivery at £14.99. If a pen looks damaged or has arrived unusually warm, contact us before using it.

Flying with Mounjaro

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.

Everyday storage habits

• Store unused pens in the main body of the fridge, not the freezer compartment or against the back wall where freezing can occur.
• Keep the cap on between uses so light does not reach the pen.
• Write the date you first used a pen on the box, so you know when the 30-day in-use window ends.
• Dispose of used needles in the sharps bin, never loose in household rubbish.

Note that a pen holds four weekly doses, which fits within the 30-day in-use limit when you inject on schedule.

If a pen has been frozen, do not use it, even if it looks normal. Contact us for advice. The same applies to a pen that has spent a long time in heat, for example in a car on a summer day.

12 · Safety and what to avoid

Safety, what to avoid and other weight loss injections

The commonest early effects of Mounjaro are mild nausea, altered appetite and tiredness in the first days after each injection, and these usually settle.¹³ Common side effects include nausea, diarrhoea, vomiting, constipation and abdominal discomfort, and they ease for most people within days to a few weeks as the body adjusts. If you notice any new symptom, discuss it with your prescriber, and report suspected side effects through the Yellow Card scheme.¹⁹

What to avoid while taking Mounjaro

The most important points to avoid are practical ones:

• Treating the injection as a replacement for a reduced-calorie diet and more physical activity. It is licensed to be used alongside both.
• Changing doses yourself, including splitting, stretching or spacing out doses. This is outside the licence and has no safety data.
• Taking two doses within 3 days of each other after a missed dose.
• Using a pen that has been frozen, or one kept out of the fridge beyond its in-use window.
• Buying from sellers who offer to supply without a consultation or prescription, because you cannot be sure the product is genuine.

Always tell your prescriber about every medicine you take, and about any change in your health. Insulin and sulfonylureas may need dose adjustments because of the risk of low blood sugar. Mounjaro slows stomach emptying, which can reduce how well oral contraceptive pills are absorbed. Switch to a non-oral method, or add a barrier method (such as condoms), for 4 weeks after starting Mounjaro and for 4 weeks after each dose increase.

Which is safer, Mounjaro or Ozempic?

Neither is safer in general. Both are licensed, prescription-only medicines with their own product information, and the right choice depends on your health, your medicines and what you are being treated for. Tirzepatide acts on two receptors, GIP and GLP-1, while semaglutide acts on one.¹ Your prescriber is the right person to weigh this for you. For semaglutide's own risks, read the Wegovy product information.¹⁸

What injections are used for weight loss?

Licensed UK options include once-weekly Mounjaro (tirzepatide) and once-weekly Wegovy (semaglutide), whose dose ladder runs 0.25mg, 0.5mg, 1mg, 1.7mg and 2.4mg, stepping up after at least 4 weeks to reach 2.4mg from week 17. Liraglutide products such as Saxenda are a daily injection, supplied at 6mg per millilitre. Wegovy tablets also exist, but for those, see their product page rather than comparing trial results. Our hub on weight loss injections sets these out side by side.

The "poor man's Ozempic"

This phrase is a marketing nickname for berberine and similar supplements. They are low-cost supplements with no clinical oversight, and their dosing is not standardised. They are not licensed weight loss medicines, and they do not work the way tirzepatide does. Be sceptical of dramatic weight-loss claims, and see our page on weight loss injection claims for how to spot them.

Mounjaro (tirzepatide) is a prescription-only medicine, supplied only after an online consultation reviewed by a GPhC-registered prescriber. Individual results vary. This page is information, not a substitute for medical advice. For a full overview, read our complete Mounjaro UK guide.

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