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
7-Day Weight Loss Detox: What the Evidence Shows
The concept of a "7-day weight loss detox" is popular in UK weight management discussions, but the evidence behind detox diets is limited. Your body naturally detoxifies through your liver and kidneys without special detox regimes. However, a structured 7-day eating plan *can* support initial weight loss through calorie reduction. The NHS recommends sustainable approaches combining reduced-calorie diets with increased physical activity. For meaningful, long-term weight management, evidence-based methods—including prescription options and lifestyle changes—are far more effective than short-term detox claims. Our free BMI calculator can help you establish your current weight health baseline before starting any weight loss journey.
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.
Understanding Detox Diets vs. Sustainable Weight Loss
Detox diets typically involve eliminating certain foods for 7 days, claiming to "flush toxins" and accelerate weight loss. However, medical evidence shows your body's detoxification systems (liver, kidneys, lymphatic system) work continuously without requiring special diets. Any initial weight loss from a 7-day detox is usually water weight and glycogen depletion, not fat loss—which returns quickly once normal eating resumes.
The NHS emphasises that sustainable weight loss involves a consistent calorie deficit of roughly 500 kcal per day, resulting in approximately 0.5 kg per week loss. This is achievable through balanced eating and physical activity, without extreme restrictions. For prescription weight loss support in the UK, GLP-1 weight loss injections like Mounjaro and Wegovy are available through NHS specialist weight management services or private prescription routes, and these work alongside lifestyle changes—not as replacements.
- Detox claims lack clinical evidence
- Short-term weight loss from detox is mostly water weight
- Sustainable loss requires consistent calorie reduction
- NHS-aligned weight management delivers lasting results
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.
Practical Alternatives to 7-Day Detox Diets
Instead of a restrictive 7-day detox, consider evidence-based weight management UK approaches: a balanced reduced-calorie diet (1,200–1,800 kcal/day depending on individual needs), increased physical activity (150 minutes moderate cardio weekly), and hydration. The NHS Weight Loss Plan offers free digital support and behaviour change strategies. If you have a BMI of 30 or above, or 27+ with weight-related health conditions like type 2 diabetes or high blood pressure, your GP can refer you to tier 3 specialist weight management services where prescription weight loss options are assessed individually. Track your progress using our free progress tracker to monitor real, sustainable changes over weeks and months rather than expecting dramatic results from a single week.
- 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.
Do 7-day detox diets actually work for weight loss?
Short-term weight loss from detox diets is mostly water and glycogen depletion, which returns quickly. The NHS recommends sustainable approaches with calorie reduction and activity, not restrictive short-term diets. Real fat loss takes weeks and consistent effort.
What does a healthy weight loss rate look like in the UK?
The NHS recommends losing 0.5 to 1 kg (1 to 2 lbs) per week. This requires a calorie deficit of around 500 kcal daily through diet and exercise combined. Faster loss increases muscle loss risk and is harder to maintain long-term.
Are there prescription options for weight loss in the UK?
Yes. GLP-1 medications like Mounjaro and Wegovy are prescription-only and available through NHS specialist weight management services or private prescription. Eligibility is assessed individually by a healthcare professional based on BMI and health conditions.
How can I check if prescription weight loss treatment is right for me?
Use our free BMI calculator to establish your current BMI. Adults with BMI 30+ or BMI 27+ with weight-related conditions may be eligible. Contact your GP for a referral to specialist weight management services, or seek a private clinical assessment from a licensed prescriber.
What's the difference between a detox diet and evidence-based weight loss?
Detox diets are restrictive, short-term, and lack clinical evidence. Evidence-based weight loss involves sustainable calorie reduction, physical activity, behaviour change, and (where appropriate) prescription medication. This approach delivers lasting results aligned with NHS guidance.
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.