Maximum Weight Loss on Mounjaro: What the Trials Show (October 2026)

01 · The core answer

What does "maximum weight loss" on Mounjaro actually mean?

It means the highest average result a trial has reported for a dose, not the most any one person could lose. The headline figure comes from the large obesity trial, where tirzepatide was taken alongside diet and exercise. 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

So the highest average belongs to 15mg. Two things matter before you treat that as your goal. First, an average has people on both sides of it. Second, the trial result is the outcome of a full programme of dose increases, diet change and activity, not of the injection 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

02 · Your decision

Is the maximum relevant to you, and what should you do next?

It is relevant as context, but a better question is what a sensible, sustainable result looks like for you. Tirzepatide is licensed for weight management in adults, and treatment is decided by a prescriber after reviewing your health, not by a target figure you pick in advance.¹ Some people reach their goal on a lower dose and stay there. Others step up. Both are normal.

If you are weighing a start, the next step is a free consultation reviewed by a GPhC-registered prescriber. The Mounjaro pen starts at £169.99 per month for the 2.5mg starting dose (standard price), and your first 2.5mg pen costs £129.99 with code FIRST40. Every dose is in stock. You can also browse our weight loss clinic for the wider picture.

Before ordering, predicted weight loss can help your expectations match the evidence.

Related guides: Biggest weight loss on mounjaro and Mounjaro expected weight loss.

03 · Trial results by dose

Trial results by dose: where the highest average comes from

The highest average weight loss for tirzepatide on a fixed dose comes from the large obesity trial, and it rises with dose. 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

Notice the shape of that result. Moving from the lowest maintenance dose to the middle one added a clear amount to the average. Moving from the middle to the top added a smaller amount. In other words, the curve flattens at the higher doses. That is useful for your decision: a bigger dose does not buy a proportionally bigger result.

The trial also reports how many people crossed particular thresholds. "At 72 weeks, 85% of participants on 5mg, 89% on 10mg and 91% on 15mg had lost at least 5% of their body weight."² And at the other end: "Half of participants on 10mg and 57% on 15mg lost at least 20% of their body weight."²

Read those together. On the highest dose, more than half the trial participants lost at least a fifth of their body weight. Yet the same data tells you that a meaningful group did not reach that level. The average is a midpoint, and real people sit on both sides of it.

How to use these figures sensibly

Treat them as a range of plausible outcomes rather than a forecast. A person who starts at a higher weight has more to lose in absolute terms for the same percentage, but percentages are the honest unit because the trial reports them that way.

Also remember the comparison group. The people in the lifestyle-only arm lost a much smaller amount, which shows that the medicine added a large effect on top of diet and activity. That is the real message of the maximum: the combination works better than either piece alone, and the medicine is one part of a plan.

If you want to see how dose decisions work in practice, read our explainers on the maximum dose of Mounjaro and what the maximum dose is. The dose ladder is licensed from 2.5mg to 15mg, and stepping through it is the prescriber's call, based on your response and how you feel.¹

04 · Averages versus individuals

Why a trial average is not your personal maximum

A trial average describes a group, and the people in that group lost very different amounts. It is the reason we avoid telling anyone they will lose a particular amount by a particular date.

Several things push an individual result above or below the average, and none of them is a secret hack. How consistently you take each weekly dose matters. So does whether you tolerate the dose increases well enough to keep going. Your eating pattern and activity matter, because the medicine is licensed for use alongside a reduced-calorie diet and increased physical activity.² Your starting point, other health conditions and other medicines can also shape the response, which is why a prescriber reviews them.

Keeping weight off after the initial loss

There is also a maintenance trial in the tirzepatide programme, which examined continuing treatment to hold on to weight reduction after the initial loss.¹⁴ Your prescriber can discuss it in the context of your plan.

A healthier question

Instead of asking how much is the most I could lose, ask what weight and health markers would make a real difference to my life, and whether I can sustain the habits that get me there. For many people the benefit is felt in appetite, energy, mobility and health measures well before they approach any ceiling.

Stepping up the dose faster than the schedule, taking extra doses or otherwise stretching the product to chase a bigger number is not safe or licensed. Dose changes are made by your prescriber, in line with the licensed schedule, and that is the safe route to whatever your best result turns out to be.

05 · Dose, titration and ceilings

Dose and titration: how people reach the top of the ladder

Mounjaro comes in six strengths: 2.5mg, 5mg, 7.5mg, 10mg, 12.5mg and 15mg, in a pre-filled multi-dose KwikPen.¹ The 2.5mg pen is the starting step.

Doses step up after at least 4 weeks on each, depending on how you respond, and the maximum trial average belongs to people who stayed on the top dose. You do not have to go all the way. The main trial shows substantial average loss at 5mg and again at 10mg, so a lower maintenance dose is a legitimate stopping point.²

Why a higher dose is not always better for you

The extra average benefit at the top of the ladder is smaller than the benefit gained earlier. If a dose increase leaves you with side effects that are hard to live with, staying put or stepping back can produce a better overall outcome than pushing on. Your prescriber can make that call with you at your regular reviews, and our aftercare includes monthly clinical reviews and side-effect support.

Equally, if you are doing well on a lower dose, there is no clinical reason to climb simply because a higher strength exists. The goal is your best sustainable result, not the highest number on the box.

Switching providers at a high dose

If you have already reached a higher dose elsewhere and want to move, a new customer receives £40 off their first order at any dose with code FIRST40, and every later order is £25 off the standard price. Each repeat order re-checks suitability, because we do not auto-ship. The standard price of the 15mg pen is £329.99 per month, and the 10mg pen is £290.99.

Costs matter when you plan a year of treatment. A first year costs £2,711.88 if you stay on 5mg after your 2.5mg starting pen, up to £3,599.88 if you step up through every dose to 15mg, at standard prices; a new customer's first order is £40 less and every later order £25 less. The Mounjaro pen page shows the live price for each dose.

Finally, the pen is for once-weekly use. Never combine pens or adjust the amount you inject yourself; follow your prescriber's instructions and the pen's own instructions for use.¹³

06 · Tirzepatide vs semaglutide

Tirzepatide versus semaglutide: the head-to-head evidence

SURMOUNT-5, the first large head-to-head trial of tirzepatide and semaglutide in people with obesity, favoured tirzepatide on average weight loss. "In SURMOUNT-5, 751 adults took tirzepatide or semaglutide 2.4mg for 72 weeks."¹⁵ The results across thresholds were: "At least 10% of body weight was lost by 81.6% on tirzepatide vs 60.5% on semaglutide; at least 15% by 64.6% vs 40.1%; at least 20% by 48.4% vs 27.3%; at least 25% by 31.6% vs 16.1%."¹⁵ And on the overall average: "Average loss was 22.8 kg vs 15.0 kg."¹⁵

The gap is widest at the higher thresholds, which is exactly where "maximum weight loss" questions live.

Keeping the comparison fair

That trial supports a direct comparison, because both medicines were studied together under the same conditions. Figures from separate trials should not be set side by side, since different populations and designs make that misleading. For context only, in STEP 1, 86.4% of adults on semaglutide 2.4mg lost at least 5% of body weight over 68 weeks, compared with 31.5% on placebo.⁹ That is an effective result for a licensed medicine, but it is not a head-to-head comparison with tirzepatide.

Mechanism and why it matters

Tirzepatide 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 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 distinguishes it from single-action GLP-1 medicines such as semaglutide.

Wegovy's ladder runs 0.25mg, 0.5mg, 1mg, 1.7mg and 2.4mg, stepping up after at least four weeks and reaching the 2.4mg maintenance dose from week 17.¹⁸ Whichever you choose, the decision belongs with a prescriber who knows your history. Both are effective, licensed treatments.

07 · When the weight comes off

When do you lose the most weight on Mounjaro?

There is no set week-by-week timetable for weight loss on Mounjaro. The 2.5mg starting step is about letting your body adjust, not about weight loss itself. Weight loss on Mounjaro is gradual by design: most measurable progress builds from 5mg onward, month by month.

The mechanism explains this. Tirzepatide slows how quickly the stomach empties and helps regulate appetite, so most people feel fuller sooner and less hungry between meals.¹ That does the work only if you then eat sensibly. Because treatment is used alongside a reduced-calorie diet and increased physical activity, the result you see depends partly on what you do with the lower appetite.²

How much can you lose by a set date?

The trial figures are reported at 72 weeks, not at interim points, so they cannot be turned into a monthly expectation. Anyone who gives you a precise weekly rate is guessing. Rather than a promise, use the trial results as a rough sense of scale and let your own reviews show your trajectory.

What helps most in practice

• Take each weekly dose consistently, on the same day, as instructed.
• Prioritise protein-rich, filling foods and smaller portions, since you will feel full sooner.
• Build in regular activity you can sustain, including resistance work if your prescriber agrees.
• Tell your prescriber early about side effects so doses can be managed rather than abandoned.
• Use a tracker such as our free GLPTrackr app to see your own pattern over time.

08 · Safety and who should aim high

Safety: why chasing the maximum is the wrong goal

Aiming for the biggest possible number can push people towards risks that the trial averages do not reveal. Mounjaro is a prescription-only medicine, 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.¹ Its licence covers adults being treated for weight management or type 2 diabetes, and the prescriber's job is to decide whether it suits you and at what dose.

Most side effects are digestive: the most common, affecting more than 1 in 10 people, are nausea, diarrhoea, vomiting, constipation and abdominal discomfort. Side effects are most likely when starting treatment or moving up a dose, and for most people they ease within days to a few weeks as the body adjusts.

Practical safety points

Dose decisions belong to your prescriber, who can weigh your response against how you are tolerating treatment. If you are using other medicines, especially insulin or sulfonylureas, tell the prescriber, because doses may need adjusting because of the risk of low blood sugar.

Tirzepatide can also reduce the absorption of oral contraceptives because stomach emptying slows, so ask about contraception when you start and when you change dose.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 Tell your prescriber about any new or lasting symptom, and you can report suspected side effects through the MHRA Yellow Card scheme.¹⁹

Loose skin and other body changes

People who ask about loose skin after a large loss are asking a fair question. Losing a significant amount of weight quickly can change facial volume and loosen skin, on any method including diet or surgery. Adequate protein, resistance exercise and a loss pace guided by your prescriber help protect lean mass; talk to your prescriber or GP if it worries you.

Finally, beware of sellers promising dramatic weight-loss claims, especially anyone offering to supply without a consultation or prescription. Genuine Mounjaro is supplied through a regulated pharmacy; ours is registered with the GPhC (9012878) and sources through official LillyDirect supply.

09 · 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

10 · NHS, private and next steps

NHS or private: how to start toward your own best result

You can reach Mounjaro through the NHS or privately, and the right route depends on your eligibility and how long you are willing to wait. The NHS position is phased: 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). Full rollout is expected to take years, which is why many people who meet the licensed criteria choose regulated private treatment rather than waiting. Ask your GP where you stand.

How ordering with us works

• Free online consultation. A short health questionnaire, with 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 delivery. Dispensed by our registered pharmacy, with same-day dispatch when ordered by 3pm and free next-day tracked delivery in temperature-controlled, discreet packaging. Saturday delivery is £14.99.

Needles, a sharps bin and injection guidance are included with every order. Your prescribing team then provides monthly reviews, dose-titration and follow-up assessments, with side-effect support. Repeat orders re-check suitability, and there is no auto-shipping or subscription lock-in. You can pay by Visa or Mastercard, with Klarna and pay-monthly options.

Planning the cost sensibly

Your first order carries the new-customer discount, and every later order is £25 off the standard price (code DOSE25). Prices were last checked 10 October 2026. Across the UK pharmacies we track, the cheapest and dearest Mounjaro pens range from £143.96 to £339.00 per month, as of 10 October 2026. The live figures for every dose sit on the Mounjaro pen page.

If you stop

Stopping is also part of the picture. After a final dose, it takes roughly 4–5 weeks for tirzepatide to clear the system, and there is no way to speed this up; nothing needs doing while it clears.¹ Stopping should always be planned with your prescriber. In SURMOUNT-4, people who stopped tirzepatide after 36 weeks regained on average 14% of body weight over the following year, while those who continued treatment lost a further 5.5% on average.¹⁴