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 a Must Calculator and How Does It Work?
A MUST (Malnutrition Universal Screening Tool) calculator is a validated UK screening method used by healthcare professionals to identify the risk of malnutrition in adults. It's particularly important in NHS practice for identifying vulnerable patients who may need nutritional support. Unlike a BMI calculator, which measures body composition, MUST assesses nutritional risk by combining BMI, unintentional weight loss, and acute illness factors. Understanding your nutritional status is a key part of overall health management alongside tracking your weight using our free BMI calculator above.
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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.
How Does MUST Assessment Work in UK Healthcare?
MUST is a three-step screening tool developed by the British Association for Parenteral and Enteral Nutrition (BAPEN). It combines three key factors: current BMI category, recent unintentional weight loss, and acute illness impact. Your GP or healthcare team uses MUST to identify patients at risk of malnutrition, particularly in hospital, care home, or community settings.
- Step 1: Calculate current BMI using your height and weight
- Step 2: Assess any unintentional weight loss in the past 3–6 months
- Step 3: Evaluate if acute illness has affected food intake in the past 2 weeks
Each factor is scored, and the total score determines nutritional risk level: low risk (0 points), medium risk (1 point), or high risk (2 or more points). If you're concerned about your weight or nutritional intake, your GP can arrange a MUST assessment as part of routine health screening. Use our free weight converter to track your weight changes alongside NHS health guidance.
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.
MUST vs BMI — What's the Difference?
BMI and MUST serve different purposes in UK healthcare. BMI (Body Mass Index) is a simple screening tool measuring weight relative to height, useful for identifying overweight or obesity. MUST goes further by examining nutritional risk, including weight change and acute illness factors—making it more sensitive for detecting malnutrition risk in vulnerable populations.
MUST is the recommended screening tool in NHS guidance for identifying patients at risk in hospital and care settings, whereas BMI is used more broadly for general population health. If you want to track your personal BMI and healthy weight range using NHS thresholds, use our free BMI calculator on this page. Your GP can explain which assessment is most relevant for your individual health needs.
- 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.
Is MUST the same as BMI?
No. BMI measures weight relative to height, while MUST is a comprehensive nutritional risk screening tool used in NHS settings. MUST includes BMI as one component, but also factors in unintentional weight loss and acute illness, making it more detailed for identifying malnutrition risk.
Who uses MUST assessments in the UK?
Healthcare professionals in NHS hospitals, care homes, and community settings use MUST to screen for malnutrition risk. GPs may also use it during routine health assessments, particularly for older adults or those with chronic health conditions.
What does a high MUST score mean?
A high MUST score (2 or more points) indicates increased risk of malnutrition and suggests the need for nutritional support or intervention. Your GP or dietitian will recommend appropriate follow-up care based on your score.
How often should MUST be assessed?
MUST should be reassessed regularly in healthcare settings—typically at each hospital admission, care home review, or when there are significant changes in health or weight. Your GP will advise on the frequency relevant to your situation.
Can I calculate my own MUST score?
You can estimate your score using MUST criteria (BMI, recent weight loss, acute illness), but a formal MUST assessment is most accurate when performed by a healthcare professional who can assess all factors reliably and provide appropriate follow-up advice.
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.