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
Weight Loss Calculator: How Much Have I Lost?
Tracking your weight loss progress is one of the most motivating steps on your health journey. Our free weight loss calculator lets you enter your starting weight and current weight to see exactly how much you've lost—in stone, kg, or lbs, whichever you prefer. Whether you're managing weight through lifestyle changes alone or exploring prescription weight loss medication available in the UK, knowing your progress helps keep you focused. This guide covers how to calculate weight loss, understand your progress, and explore your options for weight management through both NHS services and prescription options like Mounjaro and Wegovy.
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.
UK-Licensed Prescription Weight Loss Options
If you're interested in prescription support for weight management in the UK, three licensed medications are available: Mounjaro (tirzepatide), Wegovy (semaglutide), and Saxenda (liraglutide). These are GLP-1 receptor agonists—medications that work by helping regulate appetite and supporting feelings of fullness.
- Mounjaro: Dual GIP and GLP-1 agonist, once-weekly injection, doses 2.5–15 mg. Clinical trials showed average weight loss of 15–21% of body weight.
- Wegovy: GLP-1 agonist, once-weekly injection, doses 0.25–2.4 mg. Clinical data shows average weight loss around 15% of body weight.
- Eligibility: Generally available to adults with BMI 30 or above, or BMI 27–29.9 with weight-related health conditions (type 2 diabetes, high blood pressure, sleep apnoea, cardiovascular disease).
All are prescription-only medicines requiring assessment by a licensed healthcare professional. Individual results vary, and medications work alongside diet and physical activity 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.
NHS vs Private Access — How to Find Out If You're Eligible
NHS route: Request a referral from your GP to your local tier 3 specialist weight management service. NHS access is available but varies significantly by region, and waiting lists can be lengthy. Your GP can assess your eligibility and discuss options.
Private route: Online consultations with UK-licensed prescribers followed by prescription through GPhC-registered pharmacies. This route typically bypasses NHS waiting lists but involves a private cost (usually £100–£300+ monthly depending on dose).
Either way, start by talking to your GP about weight loss medication and NHS options. They can advise on your individual eligibility, discuss whether prescription medication is appropriate for you, and explain what to expect. Use our free BMI calculator above to understand your current BMI category, and track your weight loss progress with our free progress tracker to stay motivated throughout your journey.
- 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.
How do I calculate how much weight I've lost?
Subtract your current weight from your starting weight. For example, if you started at 95kg and now weigh 85kg, you've lost 10kg (or about 1st 7lbs in stone). Use our free weight loss calculator above to track this instantly in your preferred units—kg, stone, or lbs.
What is a healthy rate of weight loss?
The NHS recommends losing 0.5–1 kg (1–2 lbs) per week as a sustainable, safe rate. This typically requires a calorie deficit of about 500 kcal per day. Faster loss is possible with medical support but increases the risk of muscle loss.
How can prescription weight loss medication help me?
GLP-1 medications like Mounjaro and Wegovy may help by reducing appetite, increasing feelings of fullness, and supporting healthier eating habits. In clinical trials, they helped people lose 15–21% of body weight. However, they work best alongside diet and exercise changes.
Do I need a prescription for weight loss injections in the UK?
Yes, all licensed weight loss injections (Mounjaro, Wegovy, Saxenda) are prescription-only medicines in the UK. They require clinical assessment from a UK-licensed prescriber—either through your GP and NHS specialist services, or through private online consultations followed by pharmacy dispensing.
What should I discuss with my GP about weight loss medication?
Ask your GP about your BMI, any weight-related health conditions you have, whether you might be eligible for NHS-funded weight loss treatment, referral pathways to specialist services, and whether prescription medication could support your goals alongside lifestyle changes. They can also rule out any underlying health conditions affecting your weight.
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.