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
I'm a Celebrity Weight Loss: How Weight Management Works in the UK
The phrase "I'm a Celebrity weight loss" often refers to dramatic transformations seen on reality TV, but sustainable weight management in the UK follows evidence-based principles. Whether you're interested in prescription weight loss medication, NHS weight loss programmes, or lifestyle changes, understanding how weight loss actually works helps you make informed decisions. This guide explains the science behind weight loss, available treatment options in the UK, and how to achieve results that last.
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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.
Understanding Weight Loss and GLP-1 Medication
Weight loss occurs when you consume fewer calories than you burn, creating a calorie deficit. The NHS recommends losing weight at a rate of 0.5 to 1 kg per week for sustainable results. In recent years, GLP-1 weight loss injections like Wegovy (semaglutide) and Mounjaro (tirzepatide) have become available in the UK for eligible adults. These prescription weight loss medications work by activating natural hormone pathways that reduce appetite and increase feelings of fullness. Clinical trials showed that people using these medications alongside diet and exercise achieved an average weight loss of 15–21% of body weight. However, prescription weight loss medications are not quick fixes — they work best when combined with reduced-calorie diet and increased physical activity. Use our free GLP-1 weight loss calculator to explore potential results at different doses, and our BMI calculator to understand your current health metrics in context of NHS guidelines.
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 Weight Loss Support and Prescription Options
The NHS offers a structured approach to weight management through its tiered pathway. Tier 1 includes self-help tools and community programmes. Tier 2 provides GP-led interventions and behaviour change support. Tier 3 specialist services may prescribe weight loss medication for adults with a BMI of 30 or above, or 27 or above with weight-related health conditions such as type 2 diabetes or high blood pressure. Access to prescription weight loss medication through the NHS varies significantly by region — waiting lists can be lengthy. Alternatively, eligible adults can access Wegovy or Mounjaro through private online prescribing services following a clinical assessment from a UK-licensed prescriber. Track your progress with our free progress tracker to monitor your weight loss journey and stay motivated over time.
- 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.
What's the difference between weight loss on TV and real-world weight loss?
TV transformations often show dramatic changes over short timeframes, sometimes through extreme calorie restriction or intensive exercise programmes. Real-world sustainable weight loss, as recommended by the NHS, is slower — typically 0.5 to 1 kg per week — and combines modest calorie reduction with lifestyle changes. This approach is safer, easier to maintain long-term, and less likely to result in muscle loss or nutritional deficiencies.
Can you get Wegovy on the NHS in the UK?
Wegovy (semaglutide) is available through NHS specialist tier 3 weight management services for eligible adults. However, NHS access varies significantly by region and waiting lists can be very long. Private online prescribing is an alternative — eligible adults can access Wegovy following an online clinical assessment from a UK-licensed prescriber, typically within days rather than months.
How much weight can you lose with GLP-1 medications?
Clinical trials showed that adults using Wegovy lost an average of approximately 15% of their body weight, whilst those using Mounjaro lost 15–21% on average. Results vary significantly between individuals and depend on dose, adherence, diet, and physical activity. Weight loss typically continues for 12–16 weeks after reaching the maximum dose, then stabilises.
Is weight loss medication suitable for everyone?
No. Prescription weight loss medications are only suitable for adults with a BMI of 30 or above, or 27 or above with weight-related health conditions. Pregnancy, breastfeeding, certain medical conditions, and some medications mean some people cannot use these treatments. A prescriber assesses suitability on an individual basis following a clinical assessment.
What happens when you stop taking weight loss injections?
Weight loss injections are typically used as a long-term treatment. If you stop, appetite-regulating hormones gradually return to baseline, and weight may gradually increase over time. Many people continue on maintenance doses. Your prescriber will advise on the best approach for your individual situation and goals.
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.