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
Juice Diets For Weight Loss — What Works in the UK
Juice diets are popular for quick weight loss, but evidence suggests they're rarely sustainable long-term. Most nutritionists recommend combining dietary changes with structured support for lasting results. In the UK, prescription weight management options are now available for eligible adults alongside lifestyle changes. If you're struggling with weight management, understanding your full range of options — from dietary approaches to medical support — can help you choose the most effective path for your health. Check your BMI using our free BMI calculator to see where you stand health-wise.
10,000+ calculations today · NHS-aligned thresholds · 100% free
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 Prescription Weight Loss Options
For adults in the UK with a BMI of 30 or above (or 27 or above with weight-related health conditions), prescription weight loss medications are now available. These work alongside dietary changes, not instead of them.
- Mounjaro (tirzepatide) — A once-weekly injection that activates dual GIP and GLP-1 pathways. Clinical trials showed average weight loss of 15–21% of body weight over 72 weeks when combined with a reduced-calorie diet.
- Wegovy (semaglutide) — A once-weekly GLP-1 injection. In clinical trials, participants lost an average of approximately 15% of their body weight at the maximum dose.
- Saxenda (liraglutide) — A daily GLP-1 injection option, though less commonly prescribed than weekly alternatives.
All are prescription-only and require a clinical assessment to confirm eligibility. Try our free GLP-1 weight loss calculator to estimate potential results 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.
How to Access Weight Loss Support in the UK
NHS route: Ask your GP for a referral to your local tier 3 specialist weight management service. Availability varies by region and waiting times can be lengthy. Private route: Access prescription weight loss medications through a UK-licensed online prescriber following a clinical assessment — no NHS referral required.
Both routes require confirmation that you meet eligibility criteria: BMI of 30 or above, or BMI of 27–29.9 with weight-related conditions (type 2 diabetes, high blood pressure, sleep apnoea, or cardiovascular disease). Your GP can advise on NHS eligibility and timeframes in your area. For private access, a licensed prescriber will assess you during an online consultation.
- 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.
Are juice diets effective for long-term weight loss?
Juice diets can cause rapid short-term weight loss due to calorie reduction, but they're rarely sustainable. Most people regain weight once normal eating resumes because juice diets don't address eating habits or hunger signals. Evidence suggests combined approaches — moderate calorie deficit, whole foods, and behavioural support — work better long-term.
What's the difference between Mounjaro and Wegovy for weight loss?
Both are once-weekly injections for UK adults with eligible BMI. Mounjaro (tirzepatide) activates dual GIP and GLP-1 pathways and showed average weight loss of 15–21% in trials. Wegovy (semaglutide) is a GLP-1 agonist with average weight loss around 15%. Both require prescription and clinical assessment. Results vary individually.
Can I access weight loss injections through the NHS?
Yes, if eligible. Ask your GP for a referral to a tier 3 specialist weight management service in your area. Availability and waiting times vary significantly by region (ICB). Private access is available without NHS referral through GPhC-registered online pharmacies following a clinical assessment with a UK-licensed prescriber.
What BMI do I need to be eligible for prescription weight loss treatment in the UK?
Generally, BMI of 30 or above, or BMI of 27–29.9 if you have weight-related health conditions (type 2 diabetes, high blood pressure, sleep apnoea, cardiovascular disease). For adults of South Asian, Chinese, Black African, or Black Caribbean heritage, lower thresholds may apply. Use our free BMI calculator to check your BMI and discuss eligibility with your GP.
Do prescription weight loss injections work without diet and exercise changes?
No. Mounjaro and Wegovy are prescribed alongside a reduced-calorie diet and increased physical activity. Clinical trials showed weight loss results were achieved with combined lifestyle and medication support. Medications help regulate appetite and support feeling fuller, but dietary changes and movement remain essential for results.
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.