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 Want To Lose Weight — Here's What Works
If you want to lose weight, you're not alone — around 63% of UK adults are overweight or obese, and many are looking for effective ways to manage their weight. The good news is that weight loss is achievable through a combination of lifestyle changes, professional support, and in some cases, prescription medication. This guide covers everything you need to know about weight loss in the UK, from NHS pathways to modern medication options, so you can choose the right approach for your health and circumstances.
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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.
Sustainable Weight Loss Methods That Work
The NHS recommends losing weight at a rate of 0.5 to 1 kg per week for sustainable, healthy results. This typically requires a calorie deficit of around 500 kcal per day. Several evidence-based approaches work well:
- Reduced-calorie diet: Eating 1,200–1,500 kcal per day (women) or 1,500–1,900 kcal per day (men) alongside normal activity
- Increased physical activity: 150 minutes of moderate exercise weekly, plus strength training
- Behaviour change support: Working with a health professional to identify eating patterns and triggers
- Mediterranean diet: Strong evidence for long-term weight management and heart health
- Intermittent fasting: 16:8 or 5:2 approaches — effective for some people
Even a 5% reduction in body weight can lower blood pressure, improve blood sugar control, and reduce joint strain. Use our free BMI calculator above to establish your current weight category and healthy target range, then our progress tracker to log your journey as you make 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.
Prescription Weight Loss Options for UK Adults
If lifestyle changes alone aren't enough, prescription weight loss medication may be an option. In the UK, adults with a BMI of 30 or above, or a BMI of 27–29.9 with weight-related health conditions, may be eligible for treatment. The most commonly prescribed options are GLP-1 receptor agonist injections — medications like Wegovy (semaglutide) and Mounjaro (tirzepatide) that work alongside diet and exercise. These are prescription-only medicines available through NHS specialist weight management services or private prescribing. Clinical trials show these medications help people lose an average of 15–21% of their body weight, though individual results vary significantly. Try our GLP-1 weight loss calculator to explore potential outcomes at different doses and timeframes.
- 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 best way to start losing weight?
Begin by speaking with your GP, who can assess your health, rule out underlying conditions, and recommend the right approach for you. Use our free BMI calculator to establish your current weight category. For most people, starting with a reduced-calorie diet (around 500 kcal daily deficit), increasing physical activity to 150 minutes per week, and tracking progress works well. Your GP can also refer you to NHS weight management services for professional support.
How quickly should I expect to lose weight?
The NHS recommends losing 0.5–1 kg per week for sustainable results. Faster loss can happen initially (often water weight), but this pace is safest long-term and helps preserve muscle. Very gradual weight management (more than 1.5 kg weekly) risks muscle loss and nutritional deficiency and should only be attempted under medical supervision.
What are GLP-1 weight loss injections, and how do they work?
GLP-1 receptor agonists like Wegovy are prescription-only injections that mimic a natural gut hormone. They reduce appetite, increase feelings of fullness, and slow digestion. Clinical trials show average weight loss of 15% of body weight at standard doses. They're used alongside diet and exercise, not instead of them, and require an initial clinical assessment to confirm suitability.
Can I get weight loss injections on the NHS?
Yes, GLP-1 medications are available on the NHS through specialist tier 3 weight management services, but availability varies significantly by region and waiting times can be long. You'll need a GP referral. Private prescribing is also available through UK-licensed online prescribers following an online clinical assessment — these options typically provide faster access.
What health improvements can I expect from losing weight?
Even a 5–10% reduction in body weight can lower blood pressure, improve blood sugar control, reduce LDL cholesterol, ease joint pain, improve sleep quality, and lower risk of type 2 diabetes and heart disease. Many people also report improved energy, mood, and confidence. Your GP can help set realistic health goals based on your individual circumstances.
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.