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
Does Grapefruit Help With Weight Loss?
Grapefruit is often promoted as a weight loss aid, but the evidence is limited. While grapefruit contains compounds that may have modest metabolic effects, it's not a reliable weight loss solution on its own. For adults in the UK struggling with excess weight, prescription weight management options like Mounjaro and Wegovy offer clinically proven support. These prescription treatments, combined with dietary changes and physical activity, may help achieve meaningful weight loss for eligible adults.
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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 for Eligible Adults
If you're interested in weight management in the UK, prescription weight loss injections are available for adults who meet specific eligibility criteria. Mounjaro (tirzepatide) is a dual GIP and GLP-1 receptor agonist administered once weekly, with clinical trials showing average weight loss of 15–21% of body weight. Wegovy (semaglutide) is a GLP-1 injection also given once weekly, with evidence showing approximately clinically studied weight loss on average. Saxenda (liraglutide) is a daily GLP-1 injection option.
These are prescription-only medicines requiring clinical assessment. Eligibility typically includes: BMI of 30 kg/m² or above, or BMI of 27–29.9 kg/m² with weight-related health conditions such as type 2 diabetes, high blood pressure, or cardiovascular disease. Our GLP-1 weight loss calculator can help you understand 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 — How to Get Started
In the UK, prescription weight loss medication is available through two routes. NHS access is through specialist tier 3 weight management services, typically requiring a GP referral. However, NHS availability varies significantly by region, and waiting lists can be lengthy. Private access is available through GPhC-registered online prescribers following a clinical assessment — this route doesn't require NHS referral.
The first step is to discuss weight management options with your GP, who can assess your eligibility and discuss whether prescription treatment might be appropriate for you. They can also advise on lifestyle changes, use our BMI calculator to understand your current health metrics, and refer you to specialist services if suitable.
- 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.
Is grapefruit scientifically proven to help with weight loss?
Limited evidence supports grapefruit as a weight loss aid. Some studies suggest grapefruit compounds may have modest metabolic effects, but results are minimal and inconsistent. Grapefruit alone is not an effective weight loss strategy. For evidence-based weight management, prescription medications or lifestyle changes are more reliable options.
Can I take grapefruit with weight loss medications like Mounjaro or Wegovy?
No. Grapefruit and grapefruit juice interact with many medications, including GLP-1 injections, by affecting how your body processes them. If you're prescribed Mounjaro or Wegovy, avoid grapefruit entirely and inform your prescriber of all dietary supplements and foods you consume regularly.
What are the actual NHS-approved options for weight loss in the UK?
Prescription weight loss medications licensed in the UK include Mounjaro (tirzepatide), Wegovy (semaglutide), and Saxenda (liraglutide). These require prescription and clinical assessment. Eligibility is based on BMI and health conditions. Access is through NHS specialist services (with referral) or private prescribers.
Who is eligible for prescription weight loss treatment in the UK?
Adults with a BMI of 30 kg/m² or above, or 27–29.9 kg/m² with weight-related health conditions (type 2 diabetes, high blood pressure, cardiovascular disease) may be eligible. South Asian, Chinese, Black African, and Black Caribbean adults may have lower thresholds. Your GP or a licensed prescriber can assess your personal eligibility.
How much weight can I expect to lose with prescription weight loss medication?
Clinical trials show average weight loss of 15–21% of body weight with Mounjaro and approximately 15% with Wegovy, achieved over several months alongside reduced-calorie diet and physical activity. However, individual results vary significantly. Use our GLP-1 weight loss calculator to see potential projections based on your current weight and dose.
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.