How heavy do you need to be to get Mounjaro — and why the scales alone don't decide

The myth worth correcting first: there is no single "right weight" for Mounjaro

People searching this question often expect a specific weight in kilograms, something like "you need to be at least 90 kg". That number does not exist. The eligibility criteria for Mounjaro are built around BMI, not absolute weight, because a person's height changes everything. A 90 kg adult who is 6 ft 2 in tall has a BMI around 25.7, which is below the threshold. The same 90 kg on a person who is 5 ft 4 in produces a BMI of roughly 34.4, which is well within the licensed range. The scales alone answer the wrong question.

BMI stands for Body Mass Index and divides your weight in kilograms by the square of your height in metres. The NHS BMI calculator will give you your figure in about thirty seconds, that is the practical check worth doing before anything else. Once you have that number, the licensed thresholds make immediate sense.

Even then, BMI is a screening tool, not a verdict. Prescribers consider your full medical history, any medicines you already take, and conditions that may make tirzepatide unsuitable, regardless of where your BMI sits. If you want a fuller explanation of how heavy you have to be to get Mounjaro, including what the thresholds mean in practice, that guide is worth reading alongside this one.

The BMI thresholds that actually apply to Mounjaro in the UK

Mounjaro (tirzepatide) holds a UK licence for weight management in adults meeting one of two criteria. The first is a BMI of 30 or above, used alongside a reduced-calorie diet and increased physical activity. The second is a BMI of 27 or above, where at least one weight-related health condition is also present. Qualifying conditions include type 2 diabetes, prediabetes, high blood pressure, raised cholesterol, obstructive sleep apnoea and similar comorbidities, a prescriber will work through this with you.

For adults from South Asian, Chinese, Middle Eastern, Black African or African-Caribbean backgrounds, UK clinical guidance recognises that health risks associated with excess weight appear at lower BMI values. The thresholds in NICE's appraisal of tirzepatide (TA1026) are set 2.5 kg/m² lower for these groups, so the standard 30 threshold effectively becomes 27.5, and the 27 threshold becomes 24.5 for those with a qualifying condition. Not every provider applies this adjustment routinely, so it is worth raising with your prescriber if it is relevant to you.

It is also worth knowing that meeting a BMI threshold is necessary but not sufficient. Our page on what weight you need to be to get Mounjaro explores how BMI, height, and qualifying conditions interact to determine eligibility. Mounjaro is not licensed for adults under 18, and is not recommended during pregnancy, while breastfeeding, or when actively trying to conceive. Certain medical histories (including a personal or family history of medullary thyroid carcinoma) require careful prescriber discussion before treatment can proceed.

How the NHS eligibility criteria differ from private prescribing

NHS access to Mounjaro is much narrower than the licensed criteria above, and it is being rolled out in stages. From June 2025 the NHS began prescribing tirzepatide for adults with a BMI of 40 or above who also have four or more specific weight-related conditions from a defined list. A second cohort (adults with a BMI of 35 to 39.9 with four or more of those conditions) became eligible from June 2026. Further cohorts are planned, with the thresholds gradually widening toward the broader licensed criteria. NHS patients must also take part in wraparound diet and activity support as part of their care.

Private prescribing through a regulated online pharmacy like our Mounjaro service works to the licensed criteria: BMI 30 or above, or BMI 27 or above with a qualifying condition. There are no waiting lists, no mandatory specialist referrals and no phased cohort restrictions. A private prescription still requires a full clinical assessment, the eligibility criteria are not relaxed, the route to them is simply faster. If you are curious about what that process involves, our clinical team page explains how prescribers are involved at every stage.

For a broader look at the weight-loss options available privately alongside Mounjaro, the weight-loss treatments overview covers the landscape clearly.

What happens during the clinical assessment, and what it considers beyond BMI

Once you have established that your BMI is in range, the assessment turns to the fuller picture. A prescriber will look at your current medications, some combinations require careful thought. Women taking oral contraceptive pills should know that tirzepatide slows gastric emptying and may reduce the pill's absorption during the first four weeks of treatment and for four weeks after each dose increase; an additional non-oral method of contraception is advisable during those windows. Anyone on HRT should discuss whether a transdermal form might be preferable. Some women also notice changes to their cycle while using tirzepatide, and our page on experiencing a heavy period on Mounjaro explains what is known and when to seek advice. These are the kinds of conversations a real prescriber, not an automated form, is there to have.

Transfer patients (people switching from another provider) are asked to supply evidence of their current treatment and dose before any prescription is issued. Dose increases similarly require clinical review rather than automatic progression. If you are approaching the end of your treatment and wondering whether you need to wean off Mounjaro gradually rather than stopping all at once, that page sets out the current clinical thinking. The tirzepatide information page goes into the treatment schedule in more detail if you want to understand how titration works before your consultation.

If you have further questions about how the process works, the FAQs cover the most common ones. When you are ready to find out whether you are clinically suitable, starting a free consultation is the natural next step, a GPhC-registered prescriber reviews your answers the same day.