If you are weighing up prescription weight-loss drugs in the UK, three questions really matter: which medicines are licensed, whether you are eligible, and what they cost each month. This guide answers all three in plain English, using verified UK prices last checked on 24 August 2026. It is information only, not medical advice — a prescriber always decides whether a medicine is suitable for you.
The two leading prescription weight-loss drugs in the UK are Mounjaro (tirzepatide) and Wegovy (semaglutide), both licensed by the MHRA and available privately from GPhC-registered pharmacies or CQC-regulated clinics. Typical eligibility is a BMI of 30+, or 27+ with a weight-related condition. Mounjaro is the most effective in head-to-head trials; Wegovy is usually cheaper. Ongoing costs range from roughly £80 to over £200 a month depending on medicine, dose and provider.
What counts as a prescription weight-loss drug in the UK?
A prescription weight-loss drug is a licensed medicine that a UK prescriber can authorise after assessing your health. That prescription step is the safety mechanism: it confirms the medicine is appropriate, that your BMI and history fit the criteria, and that nothing on your medication list makes it risky. Anything sold without a consultation is not a legitimate route.
The category is dominated by the GLP-1 class of injectables, joined more recently by oral options:
- Mounjaro (tirzepatide) — a weekly injection that acts on two gut hormones (GLP-1 and GIP).
- Wegovy (semaglutide) — a weekly injection acting on GLP-1.
- Wegovy Pill (oral semaglutide) — a daily tablet version for those who prefer not to inject.
Older tablets such as orlistat still exist but produce much smaller results. For a fuller breakdown of the tablet options, see our guide to weight-loss tablets in the UK.
How well do prescription weight-loss drugs work?
The differences between medicines are real and worth understanding before you choose.
Mounjaro is the most effective option studied so far. In the SURMOUNT-1 trial, adults with obesity or overweight lost an average of 16.0% of body weight at 5 mg, 21.4% at 10 mg and 22.5% at 15 mg over 72 weeks, versus 2.4% on placebo. Around 90% of people on the 15 mg dose lost at least 10% of their body weight.
Wegovy delivered around 15% average weight loss at the 2.4 mg dose in the STEP 1 trial. In the SURMOUNT-5 head-to-head study, tirzepatide produced roughly 20% loss compared with about 14% for semaglutide.
Both are started low and increased slowly to reduce side effects. Mounjaro begins at 2.5 mg weekly for four weeks (a starter dose, not a treatment dose), then rises in steps to a maximum of 15 mg. For a side-by-side look at formats, our comparison of weight-loss injections vs tablets covers the trade-offs.
Who is eligible for prescription weight-loss drugs?
Private eligibility usually means a BMI of 30 or above, or 27 or above alongside a weight-related condition such as high blood pressure or type 2 diabetes. Mounjaro is recommended by NICE (TA1026, December 2024) and is being rolled out on the NHS in phases from 2025, prioritising those with the highest BMI and most weight-related conditions first — so NHS access still varies by area.
A prescriber makes the final call, and a good provider will decline you if the medicine is not appropriate. Our detailed guide to weight-loss medication eligibility in the UK explains the BMI rules in full.
What do prescription weight-loss drugs cost in the UK?
Because these are private medicines, prices vary widely between regulated pharmacies — even though the pen or tablet is identical. The table below shows verified starter-dose prices for the main options, including our recommended provider, The Weight Clinic.
| Medicine (starter dose) | Cheapest verified | The Weight Clinic | Typical top of range |
|---|---|---|---|
| Mounjaro 2.5 mg | £131 (Next Script) | £160 (first month £125) | £220 (Envigore) |
| Wegovy 0.25 mg | £79.99 (Next Script) | £115 (first month £80) | £164 (Juniper) |
| Wegovy Pill 1.5 mg | £86.99 (Happy Pharmacy) | £115 (first month £80) | £154 (Skin & Shape) |
For Mounjaro alone the spread is £89 a month for the same pen — £131 at the cheapest to £220 at the priciest. That is why it pays to compare rather than buy from the first name you recognise. You can see every provider on our live price table, and for a deeper dive read weight-loss medication costs compared.
The Weight Clinic is our recommended provider. It is a GPhC-registered pharmacy offering monthly video reviews with a prescriber, a refund if the prescriber declines your request, and £35 off your first order with code NEWME. That takes a first month of Mounjaro to £125 and Wegovy to £80. You can check your eligibility with The Weight Clinic here.
Costs rise as your dose increases
The starter dose is the cheapest month you will pay. As you titrate upward the price climbs — Mounjaro at 15 mg, for example, ranges from around £266 to £359 a month depending on provider. Budget for the maintenance dose, not just the introductory one, and factor in any first-month discount separately. If you are considering the tablet route, our breakdown of Wegovy injection vs Wegovy pill costs compares the two formats over time.
Side effects and safety
The most common side effects are nausea, diarrhoea, constipation, vomiting and tiredness, usually mildest early on and easing as your body adjusts. Rarer but more serious risks include pancreatitis, gallstones, dehydration that can strain the kidneys, and low blood sugar if combined with insulin or a sulfonylurea.
If you experience a side effect, you can report it through the MHRA Yellow Card scheme, which helps monitor medicine safety across the UK. Only ever buy from a GPhC-registered pharmacy or CQC-regulated clinic — never from social media sellers, marketplaces or "compounded" alternatives, which are not licensed and carry a real risk of counterfeit product.
Which prescription weight-loss drug is right for you?
If maximum weight loss is your priority and cost is manageable, Mounjaro has the strongest trial evidence. If you want a lower monthly outlay, Wegovy — or the daily Wegovy Pill if you would rather avoid injections — may suit you better. Whatever you choose, the medicine is identical across regulated providers, so it is reasonable to let price and service quality guide the decision once a prescriber has confirmed you are eligible. For the complete picture, see our complete 2026 guide to weight-loss medications in the UK.
The Weight Clinic is our recommended provider: a GPhC-registered pharmacy with monthly video reviews and a refund if the prescriber declines. New customers get £35 off the first order with code NEWME. Start your assessment with The Weight Clinic.
Frequently asked questions
What are the main prescription weight-loss drugs in the UK?
The leading options are Mounjaro (tirzepatide) and Wegovy (semaglutide), both weekly injections, plus the Wegovy Pill (oral semaglutide) for those who prefer a daily tablet. All are MHRA-licensed and require a prescriber assessment.
Which prescription weight-loss drug works best?
In trials, Mounjaro produced the largest average weight loss — up to around 22.5% at the 15 mg dose over 72 weeks, compared with about 15% for Wegovy. A head-to-head study (SURMOUNT-5) found roughly 20% vs 14% in favour of tirzepatide.
Am I eligible for prescription weight-loss medication?
Private eligibility usually requires a BMI of 30 or above, or 27 or above with a weight-related condition. A prescriber reviews your details and makes the final decision, and can decline if the medicine is not suitable.
How much do prescription weight-loss drugs cost per month?
Verified UK prices start from £131 a month for Mounjaro 2.5 mg and £79.99 for Wegovy 0.25 mg, rising with dose. Higher Mounjaro doses can reach £266–£359 a month depending on the provider.
Can I get these drugs on the NHS?
Mounjaro is being rolled out on the NHS in phases from 2025, prioritising those with the highest BMI and most weight-related conditions. Access varies by area, so many eligible people choose a regulated private pharmacy instead.
Where is it safe to buy prescription weight-loss drugs?
Only from a GPhC-registered pharmacy or CQC-regulated clinic, after a genuine prescriber assessment. Avoid social media sellers, overseas websites and "compounded" versions, which are unlicensed and may be counterfeit.