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
UPF Weight Loss Study: What UK Adults Need to Know
Research into ultra-processed foods (UPF) and weight gain has highlighted the importance of dietary choices for sustainable weight management in the UK. Understanding these findings can help you make informed decisions about your health. For many people, dietary changes alone may not be sufficient, which is why the NHS and private healthcare providers now offer prescription weight loss medication for eligible adults. If you're struggling with weight management, exploring all available options—from lifestyle changes to medication—can help you find an approach that works 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.
Prescription Weight Loss Options Available in the UK
The UK has three main prescription weight loss medications licensed for weight management in adults. Mounjaro (tirzepatide) is a once-weekly injection that works as a dual GIP and GLP-1 receptor agonist, helping to regulate appetite and reduce food cravings. Wegovy (semaglutide) is also a once-weekly injection that activates the GLP-1 pathway. Saxenda (liraglutide) is a daily injection and was the first GLP-1 medication licensed in the UK for weight management.
In clinical trials, these medications have demonstrated significant weight loss results when used alongside dietary changes and increased physical activity. Individual results vary, but participants in trials lost an average of 15–21% of their body weight over treatment periods. These medications may be particularly helpful for people who haven't achieved sustained weight loss through diet and exercise alone, and who have a BMI of 30 or above, or 27 or above with weight-related health conditions such as type 2 diabetes or high blood pressure.
Our GLP-1 weight loss calculator can help you estimate potential weight loss outcomes at different medication doses based on current clinical evidence.
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: Eligibility and Next Steps
NHS Access: Prescription weight loss medication is available through specialist tier 3 and tier 4 weight management services. You'll need a referral from your GP, and availability varies significantly by region. Waiting lists can be lengthy in many areas, but the medication is free once approved.
Private Access: Private online prescribing services offer faster access without NHS referral. A UK-licensed prescriber will assess your medical history and eligibility through an online consultation. If approved, medication is dispensed by a GPhC-registered pharmacy.
To find out if you're eligible, start by calculating your BMI using our free BMI calculator. Then discuss your weight management options with your GP, who can advise whether prescription medication is appropriate for you and explain the next steps on the NHS route. Your GP can also provide guidance on combining medication with dietary and lifestyle changes for the best outcomes.
- 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.
Does UPF research mean I should use weight loss medication?
UPF research highlights why dietary choices matter, but medication isn't the only solution. For eligible adults, prescription weight loss medicine like Mounjaro or Wegovy can support weight management alongside dietary improvements. Speak to your GP to discuss whether medication might help you.
What does GLP-1 weight loss medication actually do?
GLP-1 medications mimic a natural hormone your body produces after eating. They help you feel fuller sooner, reduce cravings, and slow how quickly food leaves your stomach. Clinical evidence shows they're effective for weight management when combined with dietary changes and physical activity.
How do I know if I'm eligible for prescription weight loss medication in the UK?
You may be eligible if your BMI is 30 or above, or 27 or above with a weight-related health condition like type 2 diabetes or high blood pressure. Use our free BMI calculator to check your BMI, then speak with your GP about whether prescription options are suitable for you.
Can I access weight loss medication through the NHS or only privately?
Both options exist in the UK. NHS access is through specialist weight management services (requires GP referral, but medication is free). Private access is faster (no referral needed) but involves a cost. Your GP can explain both routes and help you decide which suits you.
How much weight can I realistically expect to lose with prescription medication?
Clinical trials show participants lost an average of 15–21% of their body weight with GLP-1 medications over treatment periods. However, individual results vary significantly. Results depend on your starting weight, adherence to medication, and lifestyle changes. Use our GLP-1 weight loss calculator to see potential outcomes.
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.