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
Safe Quick Weight Loss — What the Evidence Shows
Quick weight loss is possible, but safety matters more than speed. The NHS recommends losing 0.5 to 1 kg per week for sustainable results that protect your health. This guide explains evidence-based weight loss approaches available in the UK, including lifestyle changes, prescription medications like Wegovy and Mounjaro, and practical strategies to help you achieve your goals safely. Whether you're aiming for weight management UK or exploring medical options, understanding how to lose weight safely ensures better long-term outcomes and reduces health risks.
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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.
How Safe Weight Loss Works
Safe weight loss requires a calorie deficit — typically around 500 kcal per day results in approximately 0.5 kg loss per week. This gradual approach preserves muscle mass and is easier to maintain long-term than crash dieting. The NHS weight loss guidance emphasises combining dietary changes with increased physical activity for best results.
Quick results are possible with medical support. Clinical trials show prescription weight loss medications like Wegovy (semaglutide) can help achieve faster results when used alongside lifestyle changes. In the STEP-1 trial, participants on Wegovy lost an average of 14.9% of their body weight over 68 weeks. However, individual results vary significantly, and prescription weight loss requires clinical assessment from your GP or a licensed prescriber.
Avoid very gradual weight management — losing more than 1.5 kg per week without medical supervision increases risks of dehydration, gallstones, muscle loss, and nutrient deficiencies. Use our free BMI calculator above to establish your starting point and set realistic targets with your healthcare provider.
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.
Prescription Options for UK Weight Loss
If diet and exercise alone haven't worked, prescription weight loss medications are available through the NHS or private prescribing. Wegovy (semaglutide) is a once-weekly GLP-1 injection licensed for weight management in UK adults with a BMI of 30 or above, or 27–29.9 with weight-related health conditions. Mounjaro (tirzepatide) is a dual GLP-1/GIP injection offering similar support. Both require a prescription and clinical assessment — they're not suitable for everyone.
These medications work alongside reduced-calorie diets and exercise, not instead of them. Our GLP-1 weight loss calculator can help you explore potential results at different doses. NHS access is through specialist tier 3 weight management services; private options are available through licensed UK prescribers. Track your progress using our free progress tracker to monitor results 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 safest rate of weight loss?
The NHS recommends 0.5 to 1 kg per week as the safest, most sustainable rate. This typically requires a calorie deficit of around 500 kcal daily. Faster loss without medical supervision increases risks of muscle loss, dehydration, and gallstones. Your GP can advise on a safe target for your individual circumstances.
Can prescription weight loss injections help me lose weight quickly?
Yes, GLP-1 medications like Wegovy may support faster weight loss when combined with diet and exercise. Clinical trials showed average losses of 14–21% body weight over 68 weeks. However, individual results vary significantly, and prescription-only medications require clinical assessment and ongoing medical supervision.
How do I access weight loss medication on the NHS in the UK?
NHS prescription weight loss treatment is typically accessed through specialist tier 3 weight management services via GP referral. Availability and waiting times vary significantly by region. Private prescription routes are also available through licensed UK prescribers with online clinical assessment, often faster but at personal cost.
Is quick weight loss bad for your health?
Very gradual weight management (>1.5 kg per week) without medical support can cause gallstones, nutrient deficiencies, muscle loss, and metabolic damage. Moderate, steady weight loss of 0.5–1 kg weekly is safer and more sustainable. Medical supervision may support faster loss when clinically appropriate.
What's the difference between Wegovy and Ozempic for weight loss?
Both contain semaglutide, but Wegovy (2.4 mg) is licensed specifically for weight management in the UK. Ozempic (up to 2 mg) is licensed for type 2 diabetes and using it off-label for weight loss is not recommended. Always use the medication your prescriber recommends based on your clinical assessment.
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.