BMI thresholds for NHS weight loss injections: the current criteria explained

Step 1, find your BMI, then look at what sits alongside it

BMI is calculated from your height and weight and gives a rough measure of body composition. The NHS BMI calculator is the quickest way to get your number. A BMI of 30 or above is classified as obese; 35 or above is severely obese. For weight loss injections on the NHS, the threshold that matters most right now is 35, but that figure only opens the door.

Alongside the BMI requirement, NHS guidance specifies a list of five weight-related conditions: high blood pressure, dyslipidaemia (raised blood fats), obstructive sleep apnoea, cardiovascular disease, and type 2 diabetes. How many of these you have determines which phase of the rollout you fall into. A BMI of 35-plus with four or more of those five conditions met the first cohort criteria from June 2025. The NHS weight loss injections page covers how these conditions interact with the access criteria in more detail.

One thing worth knowing early: some people spend weeks calculating their BMI only to discover the comorbidity count is what's holding them back, not the BMI itself. That's genuinely frustrating, and it's worth understanding the full picture before you start.

Step 2, understand the phased rollout and where we are now

The NHS is not opening access to these medicines all at once. NICE's appraisal of tirzepatide (TA1026) set out a phased implementation plan, and NHS England is following it in steps. From June 2025, the entry point was BMI 40 or above with four or more qualifying conditions. A second cohort (BMI 35 to 39.9 with four or more conditions) became eligible from around June 2026, with Cohort 2 activated on 23 June 2026. A further phase, expected around March 2027, will extend access to those with a BMI of 40 or above with three qualifying conditions.

From 1 April 2026, GP practices can prescribe under the new GP contract, though participation is optional and availability varies by practice and area. Previously, referral to a specialist weight management service was the only NHS route for semaglutide (Wegovy) under NICE's TA875 guidance, and waiting lists for those services remain long. If you want to understand the full process for applying through a GP, the guide to applying for NHS weight loss injections sets that out step by step.

Ethnic background adjustments: the 2.5 kg/m² reduction applies consistently across NICE guidance, so the 35 threshold effectively becomes 32.5, and the 40 threshold becomes 37.5, for the populations named above. This is not discretionary, it reflects NICE's own recommendations, referenced in NICE TA1026.

Step 3, check whether the private eligibility criteria fit your situation

If your BMI sits below the NHS thresholds, or you have fewer qualifying conditions than the current phase requires, the NHS route is not available to you yet. That does not mean treatment is out of reach. The licensed criteria for private prescribing follow the medicines' UK product licences: adults with a BMI of 30 or above, or 27 or above with at least one weight-related condition, can be considered for a private prescription following clinical assessment.

Weight-related conditions that count in the private context include prediabetes, hypertension, high cholesterol, obstructive sleep apnoea, and osteoarthritis, among others. A prescriber looks at the full picture, not just the BMI figure. The overview of weight loss injections explains both medicines in plain terms if you're still deciding which path to explore. For context on what private treatment costs, the weight loss injection prices page covers market pricing honestly.

One thing the private route offers that the NHS currently cannot: no waiting list, no phased access, and no requirement for multiple comorbidities. Whether that suits your circumstances is a clinical conversation, not a commercial one. Our prescribers are GPhC-registered Independent Prescribers who read your consultation personally, a real clinician, not a form-processing system.

Step 4, what happens if you meet the criteria but aren't sure which medicine is right

Both Mounjaro (tirzepatide) and Wegovy (semaglutide) are licensed for weight management in the UK. Tirzepatide acts on two gut-hormone receptors (GIP and GLP-1); semaglutide acts on one. In the SURMOUNT-5 head-to-head trial, published in the New England Journal of Medicine in 2025, tirzepatide produced a greater average weight reduction than semaglutide 2.4mg over 72 weeks. That said, which medicine is appropriate for a given person depends on their health history, other medications they take, and clinical judgement, not on headline trial figures alone.

For anyone uncertain whether their BMI and health history make them a plausible candidate, the clearest next step is a consultation. A prescriber can tell you which treatment, if any, is clinically suitable. If you want to see whether treatment might be available to you now, the treatment overview gives a plain summary of both options, including weight loss injections available for sale through a private prescription. You can also review how to spot a legitimate weight loss injection provider before committing to any service. And if you have specific questions before starting, the FAQs address the most common ones our prescribers hear.

When you're ready, speak to our prescribers through a free consultation, no referral needed, reviewed the same day.