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 Does "Lost B" Mean in a Health Context?
"Lost B" isn't a standard medical or health term used in UK NHS guidance or clinical practice. If you've encountered this phrase in a weight management, fitness, or health context, it may be slang, an abbreviation specific to a particular programme, or a misheard term. This UK health guide explains what it might mean and directs you to accurate, evidence-based information about weight management instead. Whether you're curious about weight loss, BMI, or healthy weight ranges, MyWeightCheck provides free tools and reliable information aligned with NHS guidelines.
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.
Possible Meanings and Contexts
"Lost B" could refer to several things depending on context:
- Lost body weight: If used informally to mean "lost body fat" or general weight loss, it's not a clinical term but may appear in fitness communities or weight loss programmes.
- Abbreviation in fitness tracking: Some apps or programmes use shorthand abbreviations that aren't standardised across the NHS or UK health services.
- Misheard or misspelled term: It might be a variation of "body composition", "BMI", or "baseline weight" — all properly documented health metrics.
- Programme-specific language: Private weight loss or fitness programmes sometimes use their own terminology that doesn't appear in standard NHS health resources.
If you're tracking weight loss or managing your health, it's helpful to use clear, evidence-based terms. Use our free BMI calculator above to understand your current weight status using NHS guidelines, and our weight converter to switch between kg, stone, and pounds — all standard UK measurements your GP will recognise.
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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.
How to Track Weight Loss Properly
If you're interested in monitoring weight loss, the NHS recommends focusing on measurable, clear metrics. BMI (Body Mass Index) is the standard screening tool used across UK healthcare — calculate yours instantly with the free BMI calculator on this page. The NHS also recommends tracking waist circumference (over 94cm for men or 80cm for women indicates increased health risk). Weight loss should ideally progress at 0.5–1 kg per week for sustainable, healthy results. If you're considering weight loss medication like Mounjaro or Wegovy, our GLP-1 weight loss calculator can help you understand potential outcomes. Always discuss any weight loss plan with your GP — personalised advice based on your individual health is essential.
- 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 "Lost B" an official medical term?
No. "Lost B" is not a standard NHS or clinical health term. It may be informal language used in fitness communities, app-based programmes, or private weight loss services. If you need clarity on a health term, your GP or practice nurse can explain what's meant in your specific healthcare context.
What should I track if I'm trying to lose weight?
The NHS recommends tracking BMI, waist circumference, and weight loss rate (aim for 0.5–1 kg per week). Use our free BMI calculator to monitor your BMI in the NHS categories, and keep a record of how you feel — energy levels, fitness improvements, and health markers often matter more than the number on the scales.
What's the difference between weight loss and fat loss?
Weight loss includes fat, muscle, and water loss. Fat loss is more specific. For sustainable health, you want primarily fat loss, which is why combining a healthy diet with physical activity (especially resistance training) is important. Your GP can discuss the best approach for your individual situation.
Are there UK-approved medications for weight loss?
Yes. Mounjaro (tirzepatide) and Wegovy (semaglutide) are both prescription-only weight loss medications licensed in the UK. They require a clinical assessment from a prescriber to check eligibility. Our GLP-1 weight loss calculator can help you understand potential outcomes if you're considering medication.
Should I use fitness app terminology or NHS terms with my GP?
Always use clear, standard terminology with your GP. Stick to NHS-recognised terms like BMI, healthy weight range, and waist circumference. If an app uses unfamiliar abbreviations, ask your GP what they mean — this ensures your health records are accurate and your care is properly documented.
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.