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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Personalized Weight Loss Programme with UK Prescription Medication
A personalized weight loss programme tailored to your health needs can make a real difference in achieving sustainable results. In the UK, prescription weight management medication is now available for eligible adults through both NHS specialist services and private prescribing. These medications work alongside lifestyle changes—reduced-calorie diet and increased physical activity—to support healthier weight management. Understanding your options, eligibility criteria, and how to access support is the first step toward a programme that works for you. Use our free BMI calculator to check your current health status and explore whether prescription medication might be appropriate for your situation.
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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 and Eligibility
Three prescription-only medications are currently licensed in the UK for weight management: Mounjaro (tirzepatide), Wegovy (semaglutide), and Saxenda (liraglutide). All are GLP-1 receptor agonist medications (with Mounjaro being a dual GIP/GLP-1 agonist) that may help reduce appetite and support feeling fuller after meals.
Eligibility criteria: You may be eligible for prescription weight loss medication if you have a BMI of 30 kg/m² or above, or a BMI of 27–29.9 kg/m² with weight-related health conditions such as type 2 diabetes, prediabetes, high blood pressure, or cardiovascular disease. South Asian, Chinese, Black African, and Black Caribbean adults may qualify at slightly lower BMI thresholds due to higher health risks at lower weights.
Clinical evidence shows these medications support weight loss alongside lifestyle changes. In trials, Mounjaro helped participants lose an average of 15–21% body weight, whilst Wegovy showed approximately 15% average weight loss. Individual results vary significantly. Our GLP-1 weight loss calculator can help you 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 Next Steps
NHS access: Available through specialist tier 3 weight management services following a GP referral. Availability and waiting times vary significantly by region, and some areas have lengthy waiting lists. Ask your GP about referral to local specialist services.
Private access: Available through GPhC-registered online pharmacies following an online clinical assessment by a UK-licensed prescriber. This route may be faster but involves private costs, typically ranging from £129–£320 per month depending on dose.
Start by speaking with your GP about whether prescription weight loss medication is appropriate for you. They can assess your health, discuss lifestyle changes, and explain NHS options. Your GP can also confirm whether you meet eligibility criteria for your region. A personalized approach combining clinical assessment, medication, and sustained lifestyle changes offers the best chance of long-term success.
- 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 Mounjaro, Wegovy, and Saxenda?
All three are prescription-only weight loss medications licensed in the UK. Mounjaro (tirzepatide) is a dual GIP/GLP-1 agonist given once weekly. Wegovy (semaglutide) is a GLP-1 agonist given once weekly. Saxenda (liraglutide) is a GLP-1 agonist given once daily. Clinical evidence suggests all three support weight loss when combined with lifestyle changes, but individual response varies. A prescriber will assess which is most suitable for you.
How do I know if I'm eligible for prescription 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 like type 2 diabetes, high blood pressure, or cardiovascular disease. South Asian and Black African/Caribbean adults may qualify at BMI 27.5 or above. Use our free BMI calculator to check your current BMI, then speak with your GP about eligibility and options available in your area.
Can I get prescription weight loss medication through the NHS?
Yes, prescription weight loss medication is available through NHS specialist tier 3 weight management services, but access varies significantly by region. You'll need a GP referral to a specialist service. Waiting times can be several months in many areas. Ask your GP about NHS options and local availability first. If NHS waiting times are very long, private prescribing may be an alternative.
How much weight can I expect to lose with these medications?
Clinical trials show average weight loss of 15–21% body weight with Mounjaro and approximately 15% with Wegovy over several months, alongside reduced-calorie diet and exercise. However, individual results vary considerably—some people lose more, others less. These medications work best as part of a personalized programme including lifestyle changes. Track your progress using our free progress tracker to monitor your individual response.
Are there side effects I should know about?
Common side effects include nausea, diarrhoea, constipation, and stomach pain, particularly when starting or increasing doses. These typically improve over time. Serious side effects are rare but can include pancreatitis (severe stomach pain) or gallbladder problems. Your prescriber will assess your suitability and discuss risks and benefits before issuing a prescription. Report any concerning symptoms to your 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.