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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Natural Weight Loss Aids — UK Prescription Medication Guide
When people search for natural weight loss aids, they often think of supplements or diet changes. But in the UK, there are also prescription medications available for weight management that can support your efforts. If you're interested in medical options for weight loss, this guide explains the UK-licensed medications available, who is eligible, and how to access them through the NHS or privately. These prescription options work alongside diet and exercise, not instead of them.
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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 Weight Loss Medications — What's Available
The UK has three prescription-only weight loss medications currently licensed for weight management: Mounjaro (tirzepatide), Wegovy (semaglutide), and Saxenda (liraglutide). These are called GLP-1 receptor agonists (or in Mounjaro's case, a dual GIP and GLP-1 agonist), which are injectable medications given once weekly or once daily.
Mounjaro is a once-weekly injection with doses from 2.5 mg to 15 mg. In clinical trials, participants lost an average of 15–21% of their body weight over 72 weeks—though individual results vary significantly. Wegovy is also once-weekly, with a maximum dose of 2.4 mg, and clinical trial data showed average weight loss of around 15% of body weight. Saxenda is a daily injection with a maximum dose of 3 mg.
All three medications require a prescription from a UK-licensed healthcare professional and are only available following a clinical assessment. To find out if you're eligible, use our free BMI calculator above to check your starting point, then speak with your GP or a private prescriber.
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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.
Eligibility and How to Access Weight Loss Medication in the UK
To be eligible for prescription weight loss medication, you generally need a BMI of 30 or above, or a BMI of 27–29.9 with at least one weight-related health condition (such as type 2 diabetes, high blood pressure, or sleep apnoea). If you're of South Asian, Chinese, Black African, or Black Caribbean heritage, the NHS recommends lower thresholds because these groups face higher cardiovascular risk at lower BMI levels.
NHS access: Referral to a specialist tier 3 weight management service, usually through your GP. Waiting times vary significantly by region. Private access: Online consultation with a UK-licensed prescriber, prescription issued if clinically appropriate, dispensed by a registered pharmacy. Your GP can advise on your eligibility and whether prescription weight loss options are right for you. Track your progress with our free progress tracker once you begin any weight loss journey.
- 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's the difference between natural weight loss aids and prescription medication?
Natural weight loss aids typically refer to diet changes, supplements, or lifestyle modifications. Prescription weight loss medications like Mounjaro and Wegovy are clinically proven drugs that require a GP or licensed prescriber assessment. Both approaches work best combined with reduced-calorie diet and increased physical activity.
Am I eligible for prescription weight loss medication in the UK?
You may be eligible if you have a BMI of 30 or above, or 27–29.9 with a weight-related health condition. If you're of South Asian, Chinese, Black African, or Black Caribbean heritage, lower BMI thresholds apply. Your GP or a licensed prescriber can assess your individual eligibility.
How much weight can I expect to lose with prescription medication?
Clinical trials show average weight loss of 15–21% of body weight, but individual results vary significantly. Factors include your starting weight, dose, diet, and exercise. No weight loss is assured. Always use conditional language—medication supports weight loss when combined with lifestyle changes.
Can I access weight loss medication through the NHS?
Yes. You can be referred to an NHS specialist weight management service (tier 3) by your GP. However, availability and waiting times vary considerably by region. Private options are also available through online consultation with a UK-licensed prescriber.
What side effects should I expect from weight loss injections?
Common side effects include nausea, diarrhoea, constipation, and stomach pain, particularly when starting or increasing doses. These often improve over time. Serious side effects are rare. Always discuss potential side effects with your prescriber before starting medication.
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.