Weight Requirements for GLP-1 Medicines such as Mounjaro (October 2026)

01 · The core answer

What weight do you need to qualify for a GLP-1 medicine?

You need a BMI at or above a set threshold, not a particular body weight. BMI compares your weight with your height, so two people of the same weight can sit on opposite sides of the line.

For Mounjaro, the UK product information describes weight management in adults who have a BMI of 30 kg/m² or above, or a BMI of 27 kg/m² or above with a weight-related health condition.¹ Weight-related conditions are things such as high blood pressure, type 2 diabetes, raised cholesterol or sleep apnoea. Your prescriber decides whether your condition counts.

Wegovy and other licensed weight-management medicines use similar logic, though each has its own product information. Always check the criteria for the specific medicine you are considering rather than assuming they match.

02 · Your decision

Which route fits your BMI?

If your BMI is 40 kg/m² or above and you have four or more qualifying conditions, you may fall into the earliest NHS group, so speak to your GP first. If your BMI is between 35 and 40 kg/m² with a weight-related condition, you meet the NICE recommendation, but local availability depends on the phased rollout. If your BMI is 30 kg/m² or above, or 27 kg/m² or above with a weight-related condition, you may meet the licensed criteria for private treatment.

The NHS position, in plain terms: 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).⁴ Full rollout is expected to take years, which is why many people who meet the licensed criteria choose regulated private treatment rather than waiting.

Not sure of your number? Our guide to GLP-1 BMI requirements goes deeper on the calculation, and requirements for a GLP-1 prescription covers the wider checks a prescriber makes beyond weight.

03 · What next

What to do next

Work out your BMI, note any weight-related conditions you have been diagnosed with, and list your current medicines. Those three things are what a prescriber needs first. If you meet the criteria and want to explore private treatment, you can start a free consultation for the Mounjaro pen. Your first 2.5mg pen costs £129.99 with code FIRST40 (standard price £169.99), and all six doses are in stock. Prices checked 10 October 2026.

If you are still weighing up options, our weight loss clinic page gives the broader picture. Nothing about the consultation commits you to buy, and a prescriber can decline an order that is unsuitable, with an automatic refund.

04 · How BMI is worked out

How BMI is worked out and what it measures

BMI is your weight in kilograms divided by your height in metres, squared, and it is expressed in kg/m². It is a screening number, not a verdict on your health. Prescribing criteria use it because it is simple, repeatable and easy to check across large groups of people.

The thresholds that matter for GLP-1 medicines are BMI 27, 30, 35 and 40 kg/m². Each marks a different rule. A BMI of 27 kg/m² is the lower licensed line, and it only counts when you also have a weight-related health condition.¹ A BMI of 30 kg/m² is the licensed line that applies without any other condition. A BMI of 35 kg/m² is where the NICE recommendation for NHS use begins, alongside a weight-related condition.⁴ A BMI of 40 kg/m² and above is where the earliest NHS rollout group began.

BMI has limits. It cannot tell muscle from fat, and it does not show where fat is stored. Someone with a lot of muscle can have a high BMI without carrying excess fat, which is one reason a prescriber reviews your answers rather than relying on the number alone.

Measure accurately. Use your real height rather than an estimate, and weigh yourself on a reliable scale, ideally at the same time of day. Small errors in height change the result more than most people expect, because height is squared in the formula.

If you are close to a threshold, do not try to adjust your figures to land on the right side. A prescriber reviewing your suitability needs honest information, because the medicine is prescription-only for good reasons. If your measured BMI is a little below the line, that is useful information in itself.

For a fuller walkthrough, see our guide to BMI requirements for GLP-1 prescriptions, which sets the thresholds out side by side.

05 · Weight-related conditions

Weight-related conditions and the lower BMI threshold

A weight-related condition is a health problem that excess weight causes or makes worse, and having one can bring the BMI threshold down to 27 kg/m².¹ This is the part of the criteria people most often misread, so it is worth being specific about what it does and does not mean.

Examples commonly discussed include raised blood pressure, type 2 diabetes, raised cholesterol and obstructive sleep apnoea. The list is not a checklist you can tick yourself. A prescriber looks at whether a condition is established, whether it relates to weight and whether treatment is appropriate for you.

It helps to know your own history before you apply. If you have been diagnosed with a condition, have a note of when and what you take for it. If you only suspect a condition, the sensible step is a check with your GP, not a self-declaration on a questionnaire.

Having a weight-related condition also matters on the NHS side. NICE recommends tirzepatide for adults with a BMI of at least 35 plus at least one weight-related condition, so documented conditions can affect where you sit in the phased rollout.⁴

Some guidance adjusts BMI thresholds for people from certain ethnic backgrounds, because health risks can appear at lower BMI levels for some groups. People from South Asian, Chinese, other Asian, Middle Eastern, Black African or African-Caribbean backgrounds are at higher risk of weight-related health problems at a lower BMI, so clinical thresholds are usually reduced by 2.5 kg/m² for these groups.

Finally, a condition does not cancel out other safety checks. Your medicines, other diagnoses, pregnancy plans and past reactions all feed into the decision. 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. The related guide on what the requirements for GLP-1 medicines are covers those wider checks.

06 · NHS versus private

NHS versus private: why the criteria differ

NHS criteria are narrower than the licence because the NHS has to prioritise limited capacity across the whole population. The licence describes who the medicine is approved for; NICE and NHS England decide who the NHS will fund and in what order.

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.⁴⁶

In practice, that means a person with a BMI of 32 kg/m² and a weight-related condition may meet the licensed criteria today but sit outside the current NHS groups. That gap is real, and it is the main reason private prescribing exists alongside the NHS route.

Neither route is better in every case. If you qualify for the NHS and can access it locally, that is a sensible first conversation with your GP. If you do not qualify yet, or do not want to wait, private prescribing under the licence is a legitimate alternative, provided the pharmacy is registered and a prescriber reviews you properly.

Check the registration yourself. Our registration is GPhC 9012878, and you can look it up on the GPhC register.¹² Any online supplier that offers to supply without a consultation or prescription should be avoided.

For Wegovy, NHS access runs through specialist weight-management services; ask your GP.

07 · Just below the threshold

What if your BMI is just below the threshold?

If your BMI is below the licensed threshold, a GLP-1 weight-loss medicine is generally not appropriate, and a responsible prescriber will say so. The criteria exist because the balance of benefit and risk is established for the group the medicine was tested and licensed for.¹

That can be frustrating if you are close to the line. A BMI of 26 kg/m² and one of 27 kg/m² are not meaningfully different people, but a rule needs a line somewhere. Pushing for treatment outside it, or trying to obtain it without a consultation, is where real harm can come in.

There are better routes. Speak to your GP about structured support, dietary advice or referral to a weight-management service. Increased physical activity and a reduced-calorie diet remain the foundation of any approach, and the licensed medicines are designed to be used alongside them.¹

If your BMI is a little under 30 kg/m² and you have no weight-related condition, you sit under the licensed line. If you do have a diagnosed condition, you may be above the lower line, so it is worth asking. If you are under 27 kg/m², the criteria are not met either way.

Be wary of anyone offering to supply a prescription medicine regardless of your measurements. Counterfeit and unregulated products are a known risk, and the MHRA publishes alerts and runs the Yellow Card scheme for reporting problems.⁷ Genuine treatment needs a genuine assessment.

Your BMI can change. If you re-measure after a period of lifestyle change or a new diagnosis, the answer may move.

08 · How tirzepatide works

What Mounjaro is and how it works

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

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. In practice, most people feel fuller sooner and less hungry between meals, which supports a reduced-calorie diet.¹

This dual action is what distinguishes Mounjaro from single-action GLP-1 medicines such as semaglutide (Wegovy/Ozempic).

Why does this matter for weight requirements? Because the medicine is designed to support a reduced-calorie diet in people whose health is affected by their weight. The BMI thresholds are how regulators define that group.

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 That is worth knowing before you start, because it shapes how you think about stopping.

Mounjaro is prescription-only, supplied after a consultation reviewed by a GPhC-registered prescriber. It is used alongside a reduced-calorie diet and increased physical activity. Individual results vary.

09 · What results to expect

What results to expect once you qualify

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 — individual results vary, and 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

Trial averages do not predict your own result. They describe groups, and individual people sit above and below the average. Anyone promising specific results should be treated with caution.

Do your starting weight and BMI change the outcome? In a trial, percentages are applied to a starting weight, so a heavier person loses more kilograms from the same percentage. For someone starting at 100 kg, 20.9% is about 21 kg. That is straight arithmetic from the trial average, not a forecast of your own result.

Early weight change varies a lot between people. Some notice appetite changes within the first few weeks, and others take longer. A slower start is not a sign that treatment has failed, and your prescriber reviews progress at follow-up rather than judging it by a single weigh-in.

You can find broader numbers in our GLP-1 statistics page, which brings together the key trial results in one place.

10 · Safety and the downsides

Safety, side effects and the honest downsides

Yes, there are downsides, and a good consultation covers them before you start. Like all medicines, Mounjaro can cause side effects, and most are digestive. The most common — affecting more than 1 in 10 people — are nausea, diarrhoea, vomiting, constipation and abdominal discomfort. Common effects (up to 1 in 10) include indigestion, reduced appetite, dizziness, reflux, burping, hair shedding and injection-site reactions. 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.¹³

Because the medicine slows how quickly the stomach empties, digestive effects are an area your prescriber will talk through with you. If you notice any new or worrying symptom, contact your prescriber, and you can report suspected side effects through the MHRA Yellow Card scheme.¹⁹

Other points to raise at your consultation: any diabetes medicines you take, because doses of insulin or sulfonylureas may need adjusting to avoid low blood sugar. Also tell your prescriber about contraception. 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

The hard truth people ask about is simple: these medicines are tools, not shortcuts. Treatment is used alongside a reduced-calorie diet and increased physical activity. Stopping treatment 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 lost a further 5.5% on average.¹⁴

If you are unsure whether you are suitable, ask. A short conversation with a prescriber is better than guessing, and ours is free with no obligation.

11 · 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

12 · Ordering with us

How ordering works if you meet the criteria

If you meet the criteria and want private treatment, ordering is a four-step process built around the prescriber's review. We are a GPhC-registered UK online pharmacy, and our registration is GPhC 9012878.

Step one is a free online consultation: a short health questionnaire, with no charge and no obligation. Your answers about height, weight, conditions and medicines are what the prescriber uses to check the licensed criteria.

Step two is the 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.

Step three is dispensing and dispatch. Your treatment is dispensed by our registered pharmacy, with same-day dispatch when ordered by 3pm. Step four is delivery: free next-day tracked delivery in temperature-controlled, discreet packaging. Saturday delivery is £14.99.

Our supply is official LillyDirect supply, meaning Mounjaro direct from Eli Lilly's UK distribution, with genuine KwikPens. All six doses are in stock. Needles, a sharps bin and injection guidance are included with every order.

On cost, the standard price depends on the dose: £169.99 for the 2.5mg starting pen, rising to £329.99 for the 15mg pen. 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 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 £25 less.

Aftercare is included: ongoing monthly reviews, dose titration and follow-up assessments by the prescribing team, plus side-effect support. Repeat orders re-check suitability, and there is no auto-shipping. You can view the Mounjaro pen and its prices any time, and the free GLPTrackr app helps you keep track of your journey.