Prescription Weight Loss Medication Eligibility: BMI Requirements (October 2026)

01 · Licensed criteria

BMI requirements for weight loss medication

The licensed BMI thresholds for Mounjaro are 30 or above, or 27 to 30 with a weight-related condition.¹ Weight-related conditions include high blood pressure, high cholesterol, obstructive sleep apnoea, cardiovascular disease, prediabetes and type 2 diabetes. Treatment must sit alongside a reduced-calorie diet and increased physical activity.¹

For the detail by drug, see our guides to Mounjaro BMI criteria and GLP-1 BMI requirements.

02 · Adjusted thresholds

Ethnic background and lower BMI thresholds

If you are from a South Asian, Chinese, other Asian, Middle Eastern, Black African or African-Caribbean background, clinical thresholds are usually reduced by 2.5 kg/m².¹ The reason is higher risk of weight-related health problems at a lower BMI. Your prescriber applies this during review.

03 · NHS or private

NHS or private: what is realistic

Mounjaro is available on the NHS, but access is being phased in over several years. NICE recommends it for adults with a BMI of at least 35 plus at least one weight-related condition. The primary-care rollout began in June 2025 with the highest-need groups first, initially BMI 40+ with four or more qualifying conditions.⁴⁶ Full rollout is expected to take years, so many people who meet the licensed criteria choose regulated private treatment. Ask your GP where you sit in your area's rollout.

If you meet the licensed criteria and want to go private, a Mounjaro pen starts with a 2.5mg pen at £169.99 per month standard price, and all six doses are in stock. New customers save £40 on their first order with code FIRST40, and an automatic £25 reorder discount applies to every future order (code DOSE25). Prices checked 10 October 2026.

04 · Next step

How checking your eligibility works with us

Eligibility is decided by a person, not a calculator. The process has four steps:

• Free online consultation: a short health questionnaire, no charge and no obligation.
• Prescriber review: reviewed by a GPhC-registered prescriber. Payment is taken when you place the order; if the prescriber decides the treatment is not suitable, the order is refunded automatically in full.
• Dispensing: by our registered pharmacy, with same-day dispatch when ordered by 3pm.
• Delivery: free next-day tracked delivery in discreet, temperature-controlled packaging.

Start your free consultation or buy Mounjaro once approved. Our supply is official LillyDirect, direct from Eli Lilly's UK distribution.

05 · Beyond BMI

What else a prescriber checks besides BMI

A prescriber assesses your BMI, medical history and current medicines before deciding whether treatment is suitable.¹ Meeting the BMI threshold does not promise approval, and a borderline BMI can still be approved when a qualifying condition is present.

You should not take Mounjaro if you are allergic to tirzepatide or any ingredient, or during pregnancy or while trying to conceive. 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. Extra care, or advice against treatment, applies with a history of pancreatitis, severe gut or digestive disease, diabetic retinopathy or gallbladder problems.¹³ 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.

Tell your prescriber if you or a close relative have had medullary thyroid cancer or MEN 2. 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.¹

06 · Medicines and interactions

Current medicines that affect eligibility

Because Mounjaro slows stomach emptying, it can change how quickly some oral medicines are absorbed, particularly at the start or when the dose rises.¹ Tell your prescriber about everything you take, especially warfarin or other narrow-margin medicines, insulin, or sulfonylureas, where doses may need reducing to avoid low blood sugar. No adjustment is needed for paracetamol.¹³ Mounjaro slows stomach emptying, which can reduce how well oral contraceptive pills are absorbed. Switch to a non-oral method, or add a barrier method (such as condoms), for 4 weeks after starting Mounjaro and for 4 weeks after each dose increase. This applies to the pill only.

07 · What treatment can achieve

What the trial evidence shows

In SURMOUNT-1, 2,539 adults taking tirzepatide alongside diet and exercise lost on average 15% of body weight on 5mg, 19.5% on 10mg and 20.9% on 15mg over 72 weeks, compared with 3.1% with lifestyle changes alone.² For someone starting at 100 kg, 20.9% is about 21 kg. These are trial averages and individual results vary.

At 72 weeks, 85% of participants on 5mg, 89% on 10mg and 91% on 15mg had lost at least 5% of their body weight.²

08 · Other medicines and criteria

Eligibility for other weight loss medicines

Other treatments have their own criteria. Wegovy is a once-weekly injection with its own dose ladder, covered in our Wegovy BMI requirements guide, and orlistat criteria are in our prescription fat blocker guide. Wegovy's NHS access runs through specialist weight-management services; ask your GP. For a wider overview see how weight loss injections work in the UK, our general eligibility for weight loss medication page, or all weight loss treatments.

For phentermine, your prescriber can advise on eligibility.