The UK's most complete GLP-1 guide
Every Question Answered. Every Side Effect Explained.
- How GLP-1 medications work
- Mounjaro vs Wegovy compared
- Injection instructions
- Side effects & solutions
- What to eat on treatment
- FAQs answered
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NHS Weight Loss Programme — Medication Options in the UK
The NHS offers a structured weight management pathway including lifestyle support and prescription medications for eligible adults. If you're struggling with excess weight, there are now several prescription weight loss options available through the NHS, alongside diet and exercise programmes. Understanding what's available and how to access it can help you take the first step towards better health. This guide covers UK-licensed weight loss medications, eligibility criteria, and how to discuss your options with your GP.
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Calculate Your BMI Instantly
Enter your height and weight below. Supports both imperial (stone & lbs) and metric (kg). Results include NHS category, healthy weight range, and ethnicity adjustments.
What Is BMI and Why Does It Matter?
Body Mass Index (BMI) is the most widely used screening tool for assessing whether your weight falls within a healthy range. Used by the NHS, GPs, and weight management services across the UK, BMI provides a quick snapshot of your weight relative to your height. The formula is simple: your weight in kilograms divided by your height in metres squared (kg/m²).
While BMI isn't a perfect measure — it doesn't account for muscle mass, bone density, or fat distribution — it remains the standard first step in identifying potential weight-related health risks including type 2 diabetes, cardiovascular disease, high blood pressure, and certain cancers.
The NHS also recommends adjusted thresholds for people of South Asian, Chinese, or Black African heritage — a BMI of 23 or above is classified as overweight, and 27.5 as obese. Our calculator includes this adjustment as a one-click toggle.
UK-Licensed Prescription Weight Loss Medications
Three medications are currently approved in the UK for weight management alongside a reduced-calorie diet and increased physical activity:
- Mounjaro (tirzepatide) — A dual GIP and GLP-1 receptor agonist, injected once weekly. Doses range from 2.5mg to 15mg. Clinical trials showed participants lost an average of 15–21% of body weight over 72 weeks.
- Wegovy (semaglutide) — A GLP-1 receptor agonist, injected once weekly. The maximum dose is 2.4mg. STEP trials demonstrated average weight loss of approximately 15% of body weight.
- Saxenda (liraglutide) — A daily GLP-1 injection at doses up to 3mg. Clinical evidence supports weight loss alongside lifestyle changes.
All three medications require a prescription and clinical assessment. Individual results vary significantly. These medicines may help reduce appetite and support feeling fuller after smaller meals, working best alongside dietary changes and increased physical activity.
Clinically BackedWeight Loss
No appointments. No waiting rooms. Just care — from a UK-regulated online pharmacy.
How It Works
Three simple steps to understand your weight and take action.
Enter your height and weight in our free calculator. Get your BMI, NHS category, healthy weight range, and ethnicity-adjusted thresholds instantly.
If your BMI suggests you're overweight or obese, explore our GLP-1 calculators to project potential weight loss on Mounjaro or Wegovy.
Use our progress tracker to log your weight weekly, visualise your journey with charts, and stay motivated — all stored privately in your browser.
Free Weight Loss Tools & Guides
Everything you need to understand your weight, explore medication options, and track your progress — completely free.
NHS vs Private Access and Eligibility
NHS access: Weight loss medications are available through NHS specialist tier 3 weight management services, typically following a GP referral. Availability varies significantly by region, and waiting lists can be lengthy in many areas. Your GP can discuss whether referral to a specialist service is appropriate for you.
Eligibility criteria: Adults with a BMI of 30 kg/m² or above, or 27–29.9 with weight-related health conditions (type 2 diabetes, high blood pressure, heart disease), may be considered. Lower thresholds apply for people of South Asian, Chinese, Black African, or Black Caribbean heritage due to higher health risks at lower BMI levels. Use our free BMI calculator to check your personal BMI, then discuss prescription options with your GP.
Private access: Prescription weight loss medications are also available through GPhC-registered online pharmacies following a clinical assessment with a UK-licensed prescriber, without NHS referral.
- Dual GIP/GLP-1 receptor agonist
- Up to 22.5% body weight loss (SURMOUNT-1)
- Weekly injection, dose escalation over 20+ weeks
- Available via private prescription in the UK
- Doses: 2.5mg → 5mg → 7.5mg → 10mg → 12.5mg → 15mg
- GLP-1 receptor agonist
- Up to 15–17% body weight loss (STEP trials)
- Weekly injection, 5-step dose escalation
- NHS & private prescription available
- Doses: 0.25mg → 0.5mg → 1mg → 1.7mg → 2.4mg
Mounjaro vs Wegovy: Head-to-Head
A side-by-side comparison of the two most popular GLP-1 weight loss medications available in the UK.
| Feature | Mounjaro | Wegovy |
|---|---|---|
| Drug class | Dual GIP/GLP-1 agonist | GLP-1 agonist |
| Active ingredient | Tirzepatide | Semaglutide |
| Avg. weight loss | 15–22.5% | 12–17% |
| Key trial | SURMOUNT-1 (2022) | STEP 1 (2021) |
| Max dose | 15 mg weekly | 2.4 mg weekly |
| Escalation period | 20–32 weeks | 16–20 weeks |
| Administration | Weekly injection (pen) | Weekly injection (pen) |
| NHS availability | Private prescription only | NHS & private |
| Approx. private cost | £150–£250/month | £150–£300/month |
| Common side effects | Nausea, diarrhoea, constipation | Nausea, vomiting, diarrhoea |
Data sourced from SURMOUNT-1 and STEP 1 clinical trials. Costs are approximate and vary by provider. Always consult a prescriber.
Am I Eligible for Weight Loss Medication?
In the UK, eligibility for GLP-1 weight loss medications like Mounjaro and Wegovy is based on your BMI and overall health profile.
- BMI of 30 or above (obese)
- Age 18 or over
- No contraindicated conditions
- Committed to lifestyle changes
- BMI of 27 or above
- Plus type 2 diabetes
- Or high blood pressure
- Or obstructive sleep apnoea
Use our BMI calculator to check whether your BMI falls within the eligible range.
How We Built These Tools
Every calculator and guide on myweightcheck is built with accuracy and transparency in mind. Our BMI calculator uses the standard WHO formula with NHS-aligned category thresholds. Our GLP-1 projections are modelled on published clinical trial data from SURMOUNT and STEP studies.
All data stays on your device. We don't require sign-ups, and we don't store your health information on any server. Your progress tracker saves data locally in your browser using localStorage, so only you can see it.
We're based in the UK and our tools are designed specifically for UK users — supporting stone & lbs by default, referencing NHS guidelines, using NICE-approved medication data, and linking to GPhC-registered pharmacies.
Frequently Asked Questions
Common questions about BMI, weight loss medications, and our free UK tools.
What is the NHS weight loss programme?
The NHS offers a four-tier pathway: tier 1 (self-help and community programmes), tier 2 (primary care support), tier 3 (specialist multidisciplinary services with medication options), and tier 4 (bariatric surgery). Prescription weight loss medications are typically available through tier 3 specialist services.
How much weight can I expect to lose with NHS weight loss medication?
Clinical trials show average weight loss of 15–21% of body weight with Mounjaro and around 15% with Wegovy, achieved alongside a reduced-calorie diet and increased physical activity. However, individual results vary considerably — some people lose more, others less. Your prescriber will discuss realistic expectations based on your personal circumstances.
How do I access prescription weight loss treatment through the NHS?
Contact your GP and explain that you're interested in weight management support. Your GP can refer you to your local specialist weight management service (tier 3) if appropriate. They will assess your BMI, health conditions, and medical history. Waiting lists vary by region; some areas have significant delays. Ask your GP about current availability in your area.
Am I eligible for NHS weight loss medication?
You may be eligible if you have a BMI of 30 or above, or 27–29.9 with weight-related health conditions such as type 2 diabetes, high blood pressure, or heart disease. If you're of South Asian, Chinese, Black African, or Black Caribbean heritage, lower BMI thresholds apply (27.5+). Use our free BMI calculator to check your BMI, then speak with your GP about eligibility.
What's the difference between Mounjaro and Wegovy?
Mounjaro (tirzepatide) is a dual GIP and GLP-1 agonist with doses up to 15mg weekly; Wegovy (semaglutide) is a GLP-1 agonist only, with a maximum dose of 2.4mg weekly. Clinical trial data suggests both support significant weight loss, though individual responses differ. Your prescriber will recommend the most suitable option based on your health profile and medical history. ```
Ready to take control of your weight loss journey?
Start with a free BMI check, explore your GLP-1 options, or begin tracking your progress today. No sign-up. No cost. Just results.