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
Understanding NICE Guidance on Obesity in the UK
NICE (the National Institute for Health and Care Excellence) provides evidence-based guidance on obesity management for UK healthcare professionals and patients. This guidance helps determine who may benefit from weight management support and what treatment options are available through the NHS. Understanding obesity classifications, health risks, and the support available can help you make informed decisions about your health. Whether you're wondering if you're overweight, obese according to UK thresholds, or exploring your options, this guide covers NICE's recommendations and the NHS pathway for weight management in adults.
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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
NICE guidance emphasises that obesity significantly increases the risk of serious health conditions. Excess weight affects multiple body systems and substantially raises the risk of type 2 diabetes, cardiovascular disease (heart attack, stroke), high blood pressure, and certain cancers including breast, bowel, and endometrial cancer. Sleep apnoea—where breathing stops repeatedly during sleep—is more common in adults with obesity. Joint problems, particularly osteoarthritis of the knees and hips, worsen with excess weight due to increased load on joints. Non-alcoholic fatty liver disease develops more frequently in people carrying excess weight. NICE also recognises that obesity increases the risk of gallstones, some respiratory conditions, and fertility problems. Even modest weight loss of 5–10% of body weight can significantly reduce these health risks and improve existing conditions, particularly blood sugar control and blood pressure. The NHS estimates that overweight and obesity contributes to around 1 in 13 deaths in the UK annually, making it a major public health concern.
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.
NICE-Recommended Weight Management Pathway
NICE recommends a stepped approach to weight management, starting with lifestyle changes and progressing to medical support where needed. Tier 1 involves self-help and community programmes—using free NHS resources, digital tools like our free BMI calculator and weight converter, and behaviour change support. Tier 2 includes GP-led interventions offering structured weight management programmes. Tier 3 provides specialist multidisciplinary services where adults with a BMI of 30 or above, or 27–29.9 with weight-related health conditions, may be assessed for prescription weight management medication. NICE has approved GLP-1 receptor agonist medications (such as tirzepatide and semaglutide) for eligible adults, used alongside dietary and lifestyle changes. Tier 4 addresses bariatric (weight loss) surgery for people with severe obesity and significant health complications. Your GP can refer you into this pathway and advise which tier is appropriate for your circumstances.
- 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 does NICE say about the BMI threshold for obesity in the UK?
NICE and the NHS define obesity as a BMI of 30 or above for most UK adults. For people of South Asian, Chinese, Black African, or Black Caribbean heritage, lower thresholds apply—a BMI of 27.5 or above is considered obese, as these groups face higher health risks at lower BMI levels. Use our free BMI calculator to check your personal BMI and see where you fall on the NHS scale.
Does NICE recommend weight loss medication for all overweight people?
No. NICE recommends weight loss medication for adults with a BMI of 30 or above, or 27–29.9 with weight-related health conditions such as type 2 diabetes, high blood pressure, or cardiovascular disease. Medications are used alongside reduced-calorie diet and increased physical activity, not instead of them. Individual assessment by a prescriber is always required.
What weight-related health conditions might make me eligible for NHS weight management support?
NICE recognises several weight-related conditions that may increase eligibility, including type 2 diabetes or prediabetes, high blood pressure, abnormal blood fats, obstructive sleep apnoea, and history of heart attack or stroke. Your GP can assess whether you meet the criteria for tier 2 or tier 3 support in your area.
How much weight loss does NICE recommend aiming for?
NICE recommends a sustainable loss of 0.5–1 kg per week, achieved through a calorie deficit of approximately 500 kcal per day. Even a 5–10% reduction in total body weight can significantly reduce health risks, improve blood pressure, and improve blood sugar control.
Is weight loss medication available on the NHS under NICE guidance?
Yes. NICE has approved GLP-1 receptor agonist medications for use within NHS specialist tier 3 weight management services. However, NHS availability varies significantly by region, and waiting times can be lengthy. Private prescription weight loss medication is also available through UK-licensed prescribers following a clinical assessment.
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.