Mounjaro BMI Requirements in the UK (October 2026)

01 · The short answer

What BMI do you need for Mounjaro?

You need a BMI of 30 or above, or a BMI between 27 and 30 with at least one weight-related health condition. That is the licensed position for private prescribing in the UK. 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 such as 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.¹¹ Meeting the BMI number therefore makes you eligible to be assessed. It does not mean you will automatically be approved.

If you are comparing rules across other weight-loss injections, our guide to BMI rules across weight-loss injections sets them side by side.

02 · Check your number

How to work out your BMI

BMI is your weight in kilograms divided by your height in metres squared, and the result is expressed in kg/m². Use your current, measured weight and height rather than a guess, because small errors in height change the result noticeably.

If your number lands close to a threshold, such as just under 30 or just under 27, weigh yourself on the same scales at the same time of day and measure your height without shoes. Your prescriber will rely on the figures you give, so accuracy matters for your safety as well as your eligibility.

Your BMI is a screening measure. It does not distinguish muscle from fat, which is one reason a prescriber also looks at your wider health picture.

03 · What to do next

If you meet the criteria, what happens next?

If you meet the criteria, the next step is a free online consultation, which a GPhC-registered prescriber reviews. Payment is taken when you place the order; if the prescriber decides the treatment is not suitable, the order is refunded automatically in full.

Should you be approved, treatment starts at the lowest dose. The 2.5mg starter pen has a standard price of £169.99, and new customers pay £129.99 for that first pen with code FIRST40. You can see every dose and current availability on the Mounjaro pen page, and our wider weight loss clinic explains how ongoing support works.

04 · Weight-related conditions

Which conditions count if your BMI is 27 to 30?

If your BMI is between 27 and 30, you need at least one weight-related condition for Mounjaro to be within its licence. The conditions named in the product information are high blood pressure, high cholesterol, obstructive sleep apnoea, cardiovascular disease, prediabetes and type 2 diabetes.¹

In practice, this means a diagnosis recorded by a clinician rather than a suspicion. If you have been told you have raised blood pressure, or you take a statin for cholesterol, that is the kind of information a prescriber will ask you about. Be ready to name the condition and any medicine you take for it.

Do not stretch the truth to cross a threshold. Treatment decisions rest on your medical history and your current medicines, so an inaccurate answer can put you at risk and will be picked up in your review.¹¹ If you are unsure whether a symptom counts as a condition, say so in the consultation and let the prescriber decide.

05 · Ethnic background adjustment

Do BMI thresholds change with ethnic background?

Yes, for many people they do. 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.⁴

The reason is clinical rather than administrative. The same BMI carries a different level of health risk in different populations, so a single number can understate risk for some people. A prescriber will apply the adjustment during your assessment, and you should tell them your background when you are asked.

This matters most near the edges. Someone just under the usual lower threshold may fall inside the adjusted range, while someone whose BMI is already high will be eligible either way. If you think the adjustment applies to you, mention it in your consultation rather than assuming the questionnaire will pick it up.

Our companion guide on the BMI needed for Mounjaro goes through worked examples of how the adjustment sits alongside the standard thresholds.

06 · NHS versus private criteria

How do NHS criteria differ from private ones?

NHS criteria are stricter than the licence, because the NHS has to prioritise who it treats first. Mounjaro is available on the NHS, but access is being phased in over several years.⁶ 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. That does not make private treatment a shortcut around clinical judgement. The licence still sets the BMI floor, and a prescriber still decides whether treatment is suitable.

If you are not sure which route fits you, ask your GP what the local NHS position is. Many people with a BMI between 27 and 30 plus a qualifying condition fall within the licence but outside current NHS priority groups.

Different medicines have different rules too. If you are weighing alternatives, our pages on Wegovy BMI requirements and on the fat blocker orlistat set out their own thresholds.

07 · Normal or low BMI

Can you get Mounjaro with a normal or only slightly raised BMI?

No. If your BMI is below 27, you fall outside the licensed criteria for weight management, so a prescriber will not normally approve Mounjaro for that purpose.¹ This applies whether you are in the healthy range or only a little above it.

It is a safety position, not a technicality. The criteria exist because the benefit and risk balance has been assessed in people with a higher BMI. A person in the healthy range has less to gain and the same potential for side effects.

A review of your diet and activity with a GP, dietitian or pharmacist is a sensible alternative to any medicine that falls outside the licence.

If your BMI is only a little under the threshold and you have a condition that is clearly weight-related, speak to your GP first. They can record your readings accurately. Our guide to the BMI at which Mounjaro can be used explains the same boundary from a different angle.

08 · Beyond BMI

What else does a prescriber check besides BMI?

A prescriber also checks your medical history and current medicines, because some people should not take Mounjaro whatever their BMI. You should not take it if you are allergic to tirzepatide or any of its ingredients, and it should not be used during pregnancy or while trying to conceive.¹³ 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 prescriber will take extra care, or may recommend against treatment, if you have a history of pancreatitis, severe gut or digestive disease, diabetic retinopathy, or gallbladder problems. Always share your full medical history and medicine list during consultation.¹³

Thyroid history is also relevant. In rodent studies tirzepatide caused thyroid C-cell tumours; it is not known whether this applies to humans, and no increase has been shown in human trials. As a precaution, tell your prescriber if you or a close relative have had medullary thyroid cancer or the inherited condition MEN 2.¹

This is why our consultation is reviewed by a GPhC-registered prescriber and not a scoring script. Your BMI opens the door to assessment, and your history decides whether treatment is right. Our guide on prescription criteria for weight-loss medication covers these wider checks across the whole medicine class.

09 · How the medicine works

What is Mounjaro and how does it work?

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

Many people stay on a maintenance dose below the highest strength, so the highest pen is not a target.

For context on results, 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. These are trial averages — individual results vary, and treatment works alongside a reduced-calorie diet and increased physical activity, not instead of them.²

10 · Limits of BMI

Why BMI is only a starting point

BMI is a simple screening tool, and it has limits that a good prescriber will keep in mind. It uses only height and weight. It cannot tell muscle from fat, and it cannot show where on the body fat is carried.

That is why the licence pairs lower BMI bands with a weight-related condition, and why the ethnic-background adjustment exists. The number is a proxy for health risk, not the risk itself. Someone with a very muscular build can have a high BMI and little excess fat, while someone with a lower BMI can carry meaningful health risk.

Treat BMI as one input among several. It tells a prescriber where you are on a broad scale, and the rest of your consultation tells them what is safe and sensible for you.¹¹

11 · Starting treatment safely

Getting Mounjaro safely once you qualify

Once you meet the criteria, buy only from a registered UK pharmacy that requires a consultation and a prescription. Our GPhC registration number is 9012878, and you can check it on the regulator's public register.¹² Be wary of any seller offering to supply without a consultation or prescription, because counterfeit weight-loss pens have been the subject of MHRA alerts.⁷

We supply genuine KwikPens through official LillyDirect supply, sourced directly from Eli Lilly's UK distribution. Delivery is free, next-day and tracked, in temperature-controlled packaging, with same-day dispatch when you order by 3pm. All six doses are in stock.

If you notice a side effect after starting, tell your prescriber and report it through the Yellow Card scheme.¹⁹ 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. Ongoing monthly reviews are included, and repeat orders re-check your suitability rather than shipping automatically.