What BMI Do You Need for Weight Loss Injections in the UK?

The myth: there is one fixed BMI that unlocks treatment for everyone

The most common misunderstanding is that weight loss injections run on a single cutoff, reach it, get the prescription; fall short, no chance. That is not how it works. The licensed eligibility for Mounjaro and Wegovy in the UK sits at BMI 30 or above, but a second route exists: BMI 27 or above if you have at least one weight-related comorbidity. So someone at BMI 28 with diagnosed hypertension or obstructive sleep apnoea may be clinically suitable where someone at BMI 31 with no comorbidities would also qualify, the two pathways run side by side.

There is also an ethnic-background adjustment. Under UK clinical guidance, BMI thresholds are reduced by 2.5 kg/m² for South Asian, Chinese, Middle Eastern, Black African or African-Caribbean backgrounds, reflecting evidence that cardiometabolic risk presents at lower BMI in these populations. The NHS tirzepatide information explains the licensed eligibility in plain terms and is a useful starting point.

What a number cannot capture is the clinical judgment a prescriber applies. Contraindications, current medicines, personal and family history, all of it feeds into a real decision. That is why these medicines require a prescription, not just a calculator.

What BMI do you actually need on the NHS versus going private?

NHS access and private licensed access follow different rules, and mixing them up causes real confusion.

For private treatment through a regulated online pharmacy, the bar is the licensed threshold above: BMI 30 (or 27 with a qualifying condition). Subject to clinical suitability, that is all that is required in terms of BMI.

NHS access is considerably more restrictive. NICE recommends tirzepatide (TA1026) for adults with BMI 35 or above plus at least one weight-related comorbidity, and even then through a phased rollout. The first phase, active from June 2025, covers BMI 40 or above with four or more qualifying conditions. A second phase opened in June 2026 for BMI 35–39.9 with four or more conditions. Further cohorts are planned through to 2027. You can read the full criteria in NICE's appraisal of tirzepatide (TA1026). Wegovy on the NHS runs through specialist weight management services, where waiting lists can be long.

For people who meet the licensed threshold but not the NHS criteria (or who do not want to wait) private, clinically supervised treatment is the practical alternative. Our guide to weight loss injections sets out both routes clearly.

Why your BMI is the starting point, not the finish line

Once you know your BMI sits in the right range, it is easy to assume approval follows automatically. It does not, and that is not a flaw in the system.

A prescriber checks for contraindications, for example, a personal or family history of medullary thyroid carcinoma or certain pancreatic conditions means these medicines are not suitable, regardless of BMI. Current medicines matter too: tirzepatide can reduce how quickly oral contraceptives are absorbed during the first four weeks of treatment and after each dose increase, so a clinician needs to know what you already take. Pregnancy, breastfeeding and plans to conceive are other reasons a prescriber would advise against treatment.

If you want to check your number before anything else, the NHS BMI calculator is the most straightforward tool. Once you have it, the full breakdown of BMI and weight loss injection eligibility on this site walks through what that figure means in practice, and if you are unsure whether your starting weight meets the threshold, our page on what weight you need for weight loss injections explains exactly what qualifies. And if you are close to the threshold, our page on eligibility at BMI 27 covers the comorbidity route in detail.

Treatment itself involves a titration schedule that a prescriber manages, starting at a lower dose and adjusting over time. How many injections you end up using, and over what period, depends on your response and clinical review. Our page on how many weight loss injections you need gives a realistic picture of what that looks like.

What the private route through nume looks like

If your BMI sits at 30 or above (or at 27 or above with a qualifying condition) a free consultation with one of our prescribers is the logical next step. A real clinician reads your answers the same day; not software, not a queue. If treatment is clinically appropriate, your prescription is issued and your first pen dispatched that day if you order before noon, arriving with DPD the next working day in plain packaging.

Everything is included in one transparent price: the consultation, the prescription, the medicine, delivery and aftercare seven days a week. No subscription, no auto-renewal. Current treatment costs are on the weight loss injections cost page. If you want to explore the full range of options before starting, the treatment overview is a good place to start. When you are ready, start your free consultation and a prescriber will assess your eligibility the same day.