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 Fat — What You Need to Know About Weight and Health
If you're concerned about your weight, you're not alone — around 63% of UK adults are overweight or obese according to recent data. The good news is that understanding where you stand health-wise, what defines a healthy weight, and what options are available makes a real difference. This UK health guide explains BMI, weight categories, and evidence-based approaches to weight management — all without judgment. Your GP can provide personalised health advice, but this information will help you understand the basics.
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.
Understanding Your Weight and Health Status
The first step is understanding where your weight sits in relation to health guidelines. The BMI (Body Mass Index) is the standard tool used by the NHS to categorise adult weight. You can calculate your BMI instantly using our free BMI calculator on this page — it takes seconds and gives you clarity on whether you're in the underweight, healthy weight, overweight, or obese category.
According to NHS guidelines, a healthy BMI is between 18.5 and 24.9. However, BMI has limitations — it doesn't distinguish between muscle and fat, so athletes may have a higher BMI despite being very fit. Waist circumference also matters: for men, over 94cm indicates increased health risk; for women, over 80cm. For adults of South Asian, Chinese, Black African, or Black Caribbean heritage, the NHS recommends lower BMI thresholds because these groups face higher health risks at lower weights.
- Healthy weight BMI: 18.5–24.9
- Overweight BMI: 25–29.9
- Obese BMI: 30 and above
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 Options and Getting Support
If you're concerned about your weight, there are several evidence-based approaches. The NHS recommends starting with lifestyle changes: a reduced-calorie diet (around 500 calories fewer per day leads to roughly 0.5kg weight loss per week) combined with increased physical activity. Many people find success with programmes like the NHS Weight Loss Plan or apps that track progress.
For some people, prescription weight loss medication may be appropriate. The NHS offers these through specialist tier 3 weight management services — your GP can refer you. Alternatively, private prescribing is available following an online clinical assessment. Track your weight loss journey using our free progress tracker to stay motivated and see real changes 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.
How do I know if my weight is unhealthy?
Use the NHS BMI categories as a starting point — calculate your BMI with our free calculator on this page. A BMI of 25–29.9 is overweight; 30+ is obese. However, BMI alone doesn't tell the full story. Your GP can assess your individual health risk, family history, and any weight-related conditions like high blood pressure or type 2 diabetes.
What's a realistic amount of weight to lose per week?
The NHS recommends losing 0.5 to 1kg per week for sustainable results. Faster weight loss is possible but increases the risk of muscle loss and nutrient deficiencies. Aim for a calorie deficit of around 500 kcal per day, which typically results in 0.5kg weekly loss.
Should I use weight loss injections like Mounjaro or Wegovy?
Prescription weight loss medications are only suitable for certain people and require a clinical assessment. You may be eligible if you have a BMI of 30 or above, or 27+ with weight-related health conditions like diabetes or high blood pressure. Your GP or a licensed prescriber will assess whether medication is right for you.
Can I convert my weight to check if I'm a healthy weight range?
Absolutely — use our free weight converter to switch between kg, stone, and pounds. Then calculate your BMI using the healthy weight ranges: for example, at 5ft 8in, a healthy weight is approximately 55–75kg (8st 10lbs to 11st 10lbs). Adjust these ranges based on your actual height.
What's the first step if I want to lose weight?
Start by calculating your BMI and having an honest conversation with your GP. They can assess your health, discuss any underlying conditions, and recommend evidence-based approaches tailored to you — whether that's dietary changes, physical activity, behaviour support, or in some cases, medication.
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.