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
Free tracker included with every download this week
Weight Loss Medications Available in the UK
If you're looking to manage your weight through medication, several prescription options are now available in the UK. Weight loss medications can support weight management when combined with dietary changes and increased physical activity. Understanding what's available, how they work, and whether you might be eligible is the first step toward exploring this option 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 Weight Loss Medications
Three prescription medications are currently licensed in the UK for weight management: Mounjaro (tirzepatide), Wegovy (semaglutide), and Saxenda (liraglutide). Mounjaro is a once-weekly injection that works as a dual GIP and GLP-1 receptor agonist, helping regulate appetite and food cravings. Clinical trials showed participants lost an average of 15–21% of their body weight over 72 weeks. Wegovy is also a once-weekly injection using a single GLP-1 mechanism, with trial data showing average weight loss of around 15% body weight. Saxenda is a daily injection option for those preferring an alternative to weekly dosing. All three are prescription-only medicines requiring a clinical assessment before being prescribed. Eligibility typically depends on your BMI and any weight-related health conditions. Use our free BMI calculator above to check your starting point, and our GLP-1 weight loss calculator to explore potential outcomes at different doses.
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 Getting Started
In the UK, prescription weight loss medication access through the NHS is available via specialist tier 3 weight management services — usually requiring a GP referral. However, NHS access varies significantly by region, and waiting lists can be lengthy in many areas. Private access is available through registered online prescribers following an online clinical assessment, without needing an NHS referral. Regardless of route, a prescriber will assess your individual health, BMI, and weight-related conditions to determine suitability. Your first step is always to speak with your GP, who can discuss your options, refer you to NHS services if appropriate, or signpost you to private prescribing options. Track your progress with our free progress tracker once you begin your weight management 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.
Who is 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 27–29.9 with weight-related health conditions such as type 2 diabetes, high blood pressure, sleep apnoea, or cardiovascular disease. For South Asian, Chinese, Black African, or Black Caribbean adults, lower BMI thresholds may apply due to higher health risks at lower weights. A prescriber will assess your individual eligibility.
What's the difference between Mounjaro and Wegovy?
Mounjaro (tirzepatide) is a dual GIP and GLP-1 receptor agonist with maximum dose of 15mg weekly, showing average weight loss of 15–21% in trials. Wegovy (semaglutide) is a GLP-1-only medication with maximum dose of 2.4mg weekly, showing average weight loss around 15%. Both are once-weekly injections. Individual results vary, and a prescriber will help determine which suits you best.
Can I get weight loss medication through the NHS?
Yes, weight loss medications are available through NHS specialist tier 3 weight management services, typically requiring a GP referral. However, availability and waiting times vary significantly across the UK depending on your region and local commissioning decisions. Private access is also available without an NHS referral through registered online prescribers.
How much weight will I lose with these medications?
Clinical trials show average weight loss of 15–21% of body weight, but individual results vary significantly. Weight loss depends on your starting weight, adherence to the medication, dietary changes, physical activity level, and personal metabolism. Even 5–clinically studied weight loss can bring meaningful health benefits. A prescriber can discuss realistic expectations for your situation.
Are weight loss medications safe?
All three UK-licensed medications have undergone rigorous clinical trials and regulatory approval. Common side effects include nausea, diarrhoea, and constipation, which typically reduce over time. Serious side effects are rare. However, these medications are not suitable for everyone—pregnancy, certain medical conditions, and some medications are contraindications. Your GP or prescriber will assess whether they're safe for you.
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.