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
What Is Obese Weight and How Does It Affect Your Health?
Obese weight in the UK is defined by BMI (body mass index) rather than a specific kilogram or stone figure, because healthy weight varies by height. According to NHS guidelines, an adult with a BMI of 30 or above is classified as obese. This classification is important because excess weight significantly increases the risk of serious health conditions. Understanding what counts as obese weight, and how it affects your health, is the first step toward making informed decisions about your wellbeing. Use our free BMI calculator above to check whether your weight falls into the obese range for your height.
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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.
Health Conditions Linked to Excess Weight
Excess weight and obesity are linked to numerous serious health conditions. Research shows that people with an obese BMI have significantly higher risk of type 2 diabetes—up to 80 times higher risk at severe obesity compared to people at a healthy weight. The risks also include cardiovascular disease (heart disease and stroke), high blood pressure, abnormal blood fats, and obstructive sleep apnoea.
Additionally, obesity increases risk for 13 types of cancer, including breast, bowel, and endometrial cancer. Other conditions linked to excess weight include non-alcoholic fatty liver disease, osteoarthritis (joint damage and pain), gallbladder disease, and poor mental health. In the UK, obesity costs the NHS approximately £6.5 billion annually. Even modest weight loss—just 5 to 10% of body weight—can meaningfully reduce these health risks and improve blood sugar control, blood pressure, and cholesterol levels.
For people of South Asian, Chinese, Black African, or Black Caribbean heritage, the NHS recognises that health risks occur at lower BMI thresholds due to genetic and metabolic factors. Your GP can discuss your individual health risks based on your personal health history and measurements.
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.
Support and Treatment Options Available in the UK
If you're classified as obese, support is available through the NHS and privately. The NHS offers a structured weight management pathway: tier 1 includes self-help digital tools and community programmes, tier 2 provides primary care support, and tier 3 offers specialist multidisciplinary services where prescription weight loss medication may be considered for eligible adults.
For adults with a BMI of 30 or above (or 27 or above with weight-related health conditions), prescription weight loss injections such as Mounjaro or Wegovy may be appropriate following clinical assessment. Our GLP-1 weight loss calculator can help you understand potential outcomes. Lifestyle changes—a reduced-calorie diet, increased physical activity, and behaviour change—remain essential alongside any medication. Your GP can advise on the right pathway for you and can refer you to specialist services if appropriate.
- 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 is obese weight defined in the UK?
Obese weight is defined by BMI (body mass index) rather than a specific weight in stone or kg. According to NHS guidelines, an adult with a BMI of 30 or above is classified as obese. Because healthy weight depends on height, use a BMI calculator to determine whether your weight falls into the obese range for your height. For people of South Asian or Black African heritage, NHS thresholds are lower, starting at BMI 27.5 or above.
What are the main health risks of obese weight?
Obese weight significantly increases risk of type 2 diabetes (up to 80 times higher at severe obesity), cardiovascular disease, high blood pressure, 13 types of cancer, sleep apnoea, fatty liver disease, and osteoarthritis. The NHS estimates obesity costs the system £6.5 billion annually. Losing even 5–10% of body weight can reduce these risks and improve blood sugar, blood pressure, and cholesterol levels.
How can I check if my weight is in the obese range?
Use our free BMI calculator above to enter your height and weight instantly. The calculator shows your BMI category and healthy weight range for your height according to NHS guidelines. You can also use our weight converter to see your weight in different units (kg, stone, pounds) to find relevant reference data for your measurements.
What support is available through the NHS for obese weight?
The NHS offers a weight management pathway: tier 1 includes digital tools and community programmes, tier 2 provides primary care support, and tier 3 offers specialist services where prescription weight loss medication may be prescribed. Access varies by region. Your GP can discuss options and refer you to specialist services if appropriate for your health needs.
Can prescription weight loss injections help with obese weight?
Yes, for eligible adults. Prescription weight loss injections such as Mounjaro (tirzepatide) and Wegovy (semaglutide) are available through NHS specialist services or privately following clinical assessment. These are suitable for adults with a BMI of 30 or above, or 27 or above with weight-related health conditions. Results vary, and medication is used alongside lifestyle changes, not instead of them.
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.