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 With Grapefruit — What the Evidence Actually Shows
Grapefruit is often promoted as a weight loss food, but scientific evidence for its effectiveness is limited. While grapefruit does contain beneficial nutrients and may support general health, it cannot replace a comprehensive weight loss strategy. If you're struggling with weight management in the UK, prescription medications alongside lifestyle changes may be more effective options. Your GP can assess whether you're eligible for evidence-based weight loss support.
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-Licensed Prescription Weight Loss Options
For adults looking for effective weight management in the UK, prescription medications offer stronger evidence than food-based approaches alone. Three GLP-1 medications are currently licensed for weight loss:
- Mounjaro (tirzepatide) — a dual GIP/GLP-1 injection; once weekly, maximum dose 15 mg; clinical trials showed average weight loss of 15–21% body weight
- Wegovy (semaglutide) — a GLP-1 injection; once weekly, maximum dose 2.4 mg; trials showed approximately 15% average weight loss
- Saxenda (liraglutide) — a GLP-1 injection; daily dosing, maximum 3 mg
All three are prescription-only medicines requiring clinical assessment. Eligibility depends on your BMI and health status. Calculate your BMI now using the free BMI calculator above to check your starting point. These medications work best alongside a reduced-calorie diet and increased physical activity.
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 — How to Get Started
NHS access: Referral to specialist tier 3 weight management services through your GP. Availability varies significantly by region, and waiting times can be lengthy.
Private access: Available through GPhC-registered online prescribers following a clinical consultation. No NHS referral needed.
Your first step is a conversation with your GP about your weight and health. They can assess whether prescription weight loss medication is appropriate for you, discuss NHS weight loss services in your area, or advise on private options. Use our free GLP-1 weight loss calculator to explore potential outcomes at different doses — this can help inform your discussion with your healthcare provider.
- 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 grapefruit help with weight loss?
Grapefruit contains beneficial compounds and is low in calories, but scientific evidence for significant weight loss is weak. It may support general health as part of a balanced diet, but cannot replace comprehensive weight management strategies. For stronger evidence-based support, speak to your GP about prescription weight loss options.
Can I use grapefruit with weight loss medications like Mounjaro?
No. Grapefruit juice and grapefruit can interact with many medications, including GLP-1 medications. If prescribed Mounjaro, Wegovy, or Saxenda, avoid grapefruit entirely. Always inform your prescriber of all foods and supplements you consume.
What's the difference between weight loss with diet and medication?
Diet alone requires significant calorie restriction and willpower. UK-licensed weight loss medications like Mounjaro and Wegovy work alongside reduced-calorie diet and activity to reduce appetite and support feeling fuller. Clinical trials show medications achieve 15–21% average weight loss versus 5–10% with diet alone.
Who is eligible for prescription weight loss medication in the UK?
Adults with a BMI of 30 or above, or 27 or above with weight-related health conditions (diabetes, high blood pressure, cardiovascular disease, sleep apnoea) may be eligible. Your GP or a licensed prescriber will assess your individual circumstances.
How do I find out if I'm eligible for NHS weight loss medication?
Start by speaking with your GP, who can assess your health and refer you to specialist weight management services if appropriate. Availability varies by region. You can also track your BMI using our free BMI calculator and progress tracker to monitor your health metrics before your appointment.
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.