The lowest BMI for Mounjaro — and what else the licence requires

Why 27 is the floor, and why the number alone is not enough

A BMI of 27 is the lowest figure at which tirzepatide is licensed in the UK, but the licence attaches a condition to it: you must also have at least one weight-related health condition. That condition might be prediabetes, established type 2 diabetes, high blood pressure, raised cholesterol, obstructive sleep apnoea, or cardiovascular disease. Without one of these, the threshold rises to a BMI of 30. The NHS BMI calculator is a quick way to check your own number before anything else, it takes under a minute and gives you a starting point before you speak to a clinician.

It is worth being clear about what the licence is and is not. It sets the population within which Mounjaro has been studied and authorised. A prescriber still has to consider your individual situation (your other medicines, your medical history, any contraindications) before deciding whether a prescription is appropriate. The BMI cutoff opens a door; it does not walk you through it automatically.

If you want a fuller look at how BMI maps onto eligibility across the different scenarios, our guide to BMI and Mounjaro eligibility covers the criteria in depth, including the NHS and private routes side by side.

How ethnic background adjusts the thresholds

For people of South Asian, Chinese, Middle Eastern, Black African or African-Caribbean backgrounds, UK guidance recognises that health risks associated with excess weight tend to occur at lower BMI values. The thresholds shift down by 2.5 kg/m² across the board. In practice this means the lower entry point becomes roughly 24.5 with a qualifying condition, or around 27.5 without one. These are not discretionary adjustments, they are built into the clinical guidance. NICE's appraisal of tirzepatide (TA1026) sets this out in its recommendations chapter and is the authoritative reference on the point.

This matters because it changes who falls inside or outside the licensed range. Someone at a BMI of 26 from a South Asian background, with a diagnosis of hypertension, may well meet the criteria, while the headline figure of 27 might suggest otherwise. A prescriber familiar with these nuances will work through it with you properly. Our page on Mounjaro at BMI 27 explores the borderline cases in more detail.

What happens if your BMI sits below the threshold

If your BMI is currently below 27 (or 27 without any qualifying condition) tirzepatide is not licensed for use at that weight. That is a firm position, not a grey area. Some people find that their BMI sits just under the line and wonder whether it is worth checking again later; weight management is a long-term health matter and circumstances change, so it is always worth revisiting with a clinician rather than assuming the answer is permanently no.

For those specifically asking about a BMI of 25 or 28, the detail of where those numbers fall relative to the licence is covered in the dedicated pages on Mounjaro at BMI 25 and Mounjaro at BMI 28. These are common questions, and the answers turn heavily on what health conditions, if any, are present. It is also worth understanding that a prescription below the licensed BMI range would be outside the terms of the marketing authorisation and is not something a responsible prescriber would issue.

Mounjaro is not the only licensed option. If you are exploring what is available to you, our weight-loss treatment overview covers the licensed medicines and how they differ, which can help you go into a consultation with the right questions.

How the decision is made in practice at nume

Every consultation at nume is read by a GPhC-registered Independent Prescriber, a real clinician, not an automated system. They consider your BMI, your reported health conditions, your current medicines, and your overall medical history. Identity is verified with photo ID, and weight is confirmed on video. Nothing is rubber-stamped.

If you are close to a threshold, that conversation matters. A prescriber who knows the licence criteria in detail can tell you clearly whether you qualify and, if you do not, why, and what options might be relevant instead. The full overview of what tirzepatide is and how it works is on our Mounjaro information page if you want to read across the medicine before deciding whether to consult. For people who have already decided and want to understand what getting a prescription privately involves, how to get Mounjaro through a UK online pharmacy explains the process step by step.

If you are ready to find out whether you are eligible, speak to our prescribers through a free consultation, there is no obligation and no prescription is issued unless it is clinically appropriate.