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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Weight Loss Medication Available in the UK
If you're looking to lose weight in the UK, prescription weight loss medication may be an option worth exploring with your GP. While diet and exercise remain the foundation of sustainable weight management, several clinically proven medications are now available to help support your efforts. These prescription options are part of a comprehensive weight management uk approach and can be accessed through either NHS specialist services or private online prescribing. This guide explains how these medications work, who may be eligible, and how to explore whether they're right for you.
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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 Weight Loss Medications Explained
Three prescription medications are currently licensed in the UK for weight management in adults: Mounjaro (tirzepatide), Wegovy (semaglutide), and Saxenda (liraglutide). Mounjaro and Wegovy are once-weekly injections, whilst Saxenda is a daily injection.
Both Mounjaro and Wegovy work as GLP-1 receptor agonists (with Mounjaro also activating the GIP pathway), helping to reduce appetite, support feeling fuller after smaller meals, and slow digestion. In clinical trials, Mounjaro helped participants lose an average of 15–21% of their body weight, whilst Wegovy showed average losses of around 15%, though individual results vary significantly.
These are prescription-only medicines requiring a clinical assessment before dispensing. Your eligibility depends on your BMI, medical history, and any weight-related health conditions. Using our free BMI calculator above, you can check where your weight sits relative to NHS thresholds—a useful first step before speaking to your GP about prescription weight loss options.
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 Access vs Private Prescribing in the UK
NHS route: Weight loss medication medication nhs access is through specialist tier 3 weight management services. Your GP can refer you, though waiting times vary significantly by region and availability can be limited. The NHS has approved tirzepatide (Mounjaro) and semaglutide (Wegovy) for use within these services, but access depends on your local integrated care board.
Private route: Prescription weight loss uk is also available through GPhC-registered online pharmacies following a clinical assessment with a UK-licensed prescriber. This route doesn't require an NHS referral and is generally more accessible, though costs vary by dose and provider. Whichever route you choose, start by having an honest conversation with your GP about your weight loss goals and whether medication might support you.
- 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.
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 a BMI of 27–29 with weight-related health conditions such as type 2 diabetes, high blood pressure, or sleep apnoea. A licensed prescriber will assess your individual circumstances. Use our free BMI calculator to check your current BMI as a starting point.
How quickly will I lose weight with these medications?
Clinical trials show average weight losses of 15–21% of body weight over 68–72 weeks, but individual results vary significantly. Weight loss is gradual and depends on your diet, physical activity, and how your body responds. These medications work best alongside a reduced-calorie diet and increased physical activity.
What's the difference between Mounjaro and Wegovy?
Both are once-weekly injections for weight management. Mounjaro is a dual GIP/GLP-1 agonist and showed slightly higher average weight loss in trials (15–21% vs 15%). Wegovy is a GLP-1 agonist only. Choice depends on clinical assessment, availability, and individual suitability—your prescriber will advise which is appropriate for you.
Can I access weight loss medication through the NHS?
Yes, through NHS specialist weight management services (tier 3). Your GP can refer you, though waiting times and availability vary by region. Private prescribing through online pharmacies is also available without an NHS referral and typically offers faster access, though with associated costs.
What side effects should I expect?
Common side effects include nausea, diarrhoea, constipation, and reduced appetite—these often improve over time. Serious side effects are rare but may include pancreatitis or gallbladder problems. Always discuss potential side effects with your prescriber and report any concerning symptoms to your GP or healthcare provider immediately.
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.