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 a 3 Day Juice Cleanse Help With Weight Loss?
A 3 day juice cleanse may result in short-term weight loss, but most of this is water and glycogen rather than fat. The NHS does not recommend juice cleanses as a weight loss strategy because they're typically low in protein, high in sugar, and unsustainable. While you might see the scales drop temporarily, the weight usually returns once you resume normal eating. For genuine, sustainable weight management in the UK, evidence-based approaches—and in some cases prescription medication following clinical assessment—are more effective long-term solutions.
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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.
Why Juice Cleanses Don't Work for Lasting Weight Loss
Short-term water loss, not fat loss: Most weight lost on a juice cleanse is water, glycogen depletion, and digestive tract contents—not body fat. Once you resume eating normally, this weight returns within days.
High sugar content: Even "healthy" juices contain concentrated natural sugars without the fibre of whole fruit. This causes blood sugar spikes, increased hunger later, and doesn't support sustainable weight management.
Low in protein: Juice cleanses lack adequate protein, which means your body may lose muscle tissue alongside any fat loss. The NHS emphasises that sustainable weight loss requires balanced nutrition.
Hunger and fatigue: Very low calorie intake (typical for juice cleanses) leaves you hungry, tired, and more likely to overeat when the cleanse ends, creating a yo-yo pattern.
No behaviour change: A 3 day cleanse doesn't teach healthy eating habits, so weight returns when normal eating resumes. Check your BMI using our free BMI calculator to see where you stand, then focus on sustainable changes.
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.
What Actually Works for Weight Loss in the UK
The NHS recommends losing weight at a rate of 0.5–1 kg per week through a combination of reduced-calorie eating and increased physical activity. For eligible adults, prescription weight loss medications like GLP-1 injections (Wegovy, Mounjaro) can support this process alongside lifestyle changes. These medications work by reducing appetite and helping you feel fuller—evidence shows Wegovy users lose approximately 15% of their body weight on average, with individual results varying.
Our free GLP-1 weight loss calculator can help you explore potential outcomes if you're eligible for prescription support. For most people, the key to lasting weight loss is creating sustainable habits: balanced meals with adequate protein, regular movement, and consistent tracking. Use our free progress tracker to log your weight loss journey and stay motivated.
- 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.
Will I lose weight on a 3 day juice cleanse?
You will likely see the scales drop 2–5 kg, but this is mostly water and glycogen, not fat loss. The weight returns within days of resuming normal eating, which is why juice cleanses are not recommended by the NHS for sustainable weight loss.
Is a juice cleanse safe?
Short-term juice cleanses are generally safe for most people, but they can cause fatigue, headaches, and dizziness due to very low calorie intake. People with diabetes, on medications, or with medical conditions should consult their GP before attempting any restrictive diet.
What's a better approach than juice cleanse for real weight loss?
The NHS recommends a calorie deficit of around 500 kcal per day through balanced eating and activity, aiming for 0.5–1 kg loss per week. For eligible individuals, prescription weight loss medication combined with lifestyle changes offers evidence-based support. Your GP can advise what's right for you.
Can I do a juice cleanse alongside weight loss medication?
No. If you're taking prescription weight loss medication like Wegovy or Mounjaro, you need adequate nutrition and stable calorie intake—not restrictive cleanses. These medications work best alongside balanced eating, not extreme restriction. Always follow your prescriber's guidance.
How do I know if I need weight loss support?
Use our free BMI calculator to check your current BMI. Adults with a BMI of 30 or above, or 27+ with weight-related health conditions, may be eligible for prescription weight loss medication through the NHS or private prescribing. Chat with your GP to explore options suited to your health.
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.