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 — Evidence-Based UK Health Guide
Weight loss is one of the most common health goals in the UK, yet sustainable results require understanding both the science and practical strategies involved. Whether you're looking to lose weight for health reasons or to reach a healthier BMI, this guide covers evidence-based approaches supported by NHS guidance. We'll explore dietary methods, activity levels, medication options, and how to set realistic goals. Use our free BMI calculator to assess your starting point, and our weight converter to understand measurements in stone, pounds, and kilograms — all essential tools for tracking your UK health information.
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.
How Much Weight Can You Lose Safely?
The NHS recommends losing weight at a rate of 0.5 to 1 kg (1 to 2 lbs) per week for sustainable, healthy results. This translates to approximately 2 to 4 kg per month — a pace that allows your body to adapt and helps preserve muscle mass. Faster weight loss is possible under medical supervision, but rapid loss (more than 1.5 kg per week) increases the risk of nutritional deficiencies, muscle loss, and metabolic slowdown.
A calorie deficit of around 500 kcal per day typically results in losing approximately 0.5 kg weekly. This can be achieved through dietary changes, increased physical activity, or a combination of both. The key to success is finding an approach you can maintain long-term — one-off diets rarely work, but sustainable lifestyle changes do.
- Weight loss should be gradual and steady
- Individual results vary based on age, genetics, and starting weight
- Medical supervision is advisable for very rapid loss
- Both diet and activity matter for sustainable 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.
Weight Management Methods Supported by Evidence
Evidence-based weight loss methods include reduced-calorie eating plans, increased physical activity, and behavioural changes. The Mediterranean diet has strong evidence for both weight loss and cardiovascular health. Intermittent fasting approaches (like 16:8 or 5:2) can work for some people but require consistency.
For adults meeting NHS eligibility criteria — a BMI of 30 or above, or 27 to 29.9 with weight-related health conditions — prescription weight loss medications may be considered as part of a comprehensive programme. These are used alongside dietary changes and activity, not instead of them. Our GLP-1 weight loss calculator can help estimate potential results if medication is appropriate for you. Your GP can assess whether treatment suits your individual health situation.
- 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 and fat loss?
Weight loss includes muscle, water, and fat. Fat loss is the specific reduction in body fat. For sustainable health, you want to lose fat while preserving muscle — achieved through moderate calorie deficit, adequate protein, and strength activity. gradual weight management often includes significant muscle loss, which is why gradual loss is recommended.
How long does it take to see weight loss results?
Most people notice changes after 3 to 4 weeks of consistent effort. Initial loss in the first 1 to 2 weeks is often water weight. True fat loss becomes visible over 4 to 8 weeks. Use our progress tracker to log changes and stay motivated — many people find tracking helpful even before seeing physical changes.
Can I lose weight without exercise?
Yes — weight loss is primarily driven by calorie deficit, which diet creates. However, exercise provides additional benefits: improved cardiovascular health, muscle preservation, better blood sugar control, and mental health benefits. Combining dietary changes with activity produces better long-term results than diet alone.
What health conditions can weight loss improve?
Even a 5 to 10% reduction in body weight can improve type 2 diabetes control, blood pressure, cholesterol levels, joint pain, sleep apnoea severity, and overall cardiovascular health. Weight loss also reduces risk of certain cancers and improves mental wellbeing. Your GP can identify which benefits are most relevant to your health.
Are prescription weight loss medications safe?
Prescription weight loss medications approved in the UK (such as GLP-1 injections) have undergone rigorous clinical trials and are monitored by the MHRA. They're prescription-only because they require medical assessment and ongoing monitoring. Side effects are possible and vary individually — your prescriber will discuss these before you start treatment.
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.