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
Basal Metabolic Rate and Weight Loss Medication in the UK
Your basal metabolic rate (BMR) is the number of calories your body burns at rest — it's a key number in weight management. Understanding your BMR helps explain why weight loss varies between individuals and why some people respond differently to diet and exercise. In the UK, prescription weight loss medication options are now available for eligible adults alongside lifestyle changes. This guide explains how BMR relates to weight loss and what prescription options exist through the NHS and private routes.
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.
UK-Licensed Prescription Weight Loss Options
Three prescription-only medications are currently licensed in the UK for weight management: Mounjaro (tirzepatide), Wegovy (semaglutide), and Saxenda (liraglutide). All three work by activating GLP-1 pathways in the brain, which help reduce appetite and support feeling fuller after smaller meals. These are not replacements for diet and exercise — they work alongside lifestyle changes to help achieve sustainable weight loss.
Eligibility typically includes adults with a BMI of 30 kg/m² or above, or 27–29.9 kg/m² with weight-related health conditions such as type 2 diabetes, high blood pressure, or cardiovascular disease. In clinical trials, Mounjaro helped participants lose an average of 15–21% of body weight, whilst Wegovy supported approximately clinically studied weight loss — though individual results vary significantly. All three are available through NHS specialist weight management services or via private online prescribing following a clinical assessment.
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.
NHS vs Private Access and Next Steps
Accessing prescription weight loss medication in the UK works through two main routes. NHS access requires referral to your local tier 3 specialist weight management service — available through your GP — though waiting times can be lengthy depending on your region. Private access is available through GPhC-registered online pharmacies following an online clinical assessment with a UK-licensed prescriber, typically without an NHS referral.
To find out if you're eligible, use our free BMI calculator above to check your current BMI. If you're interested in prescription weight loss support, speak to your GP about NHS options in your area, or explore private prescribing services. Either way, a qualified prescriber will assess your individual health before recommending treatment.
- 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 is basal metabolic rate and why does it matter for weight loss?
Your BMR is the number of calories your body burns at rest to maintain basic functions like breathing and circulation. It varies based on age, sex, muscle mass, and genetics. Understanding your BMR helps explain why weight loss differs between people — those with higher BMR burn more calories naturally, but sustainable loss still requires a calorie deficit alongside lifestyle changes or medical support.
How do Mounjaro and Wegovy relate to BMR and weight loss?
Mounjaro and Wegovy don't directly change your BMR. Instead, they reduce appetite and help you eat fewer calories naturally by making you feel fuller. When combined with reduced calorie intake and physical activity, this calorie deficit leads to weight loss — though the rate depends on your individual metabolism, BMR, and lifestyle adherence.
Am I eligible for prescription weight loss medication on the NHS?
Generally, yes, if you have a BMI of 30 or above, or 27–29.9 with weight-related health conditions. However, NHS availability varies significantly by region. Your GP can assess your eligibility and refer you to a specialist weight management service. Waiting times can be several months in some areas.
What's the difference between NHS and private weight loss medication access?
NHS access requires a GP referral and wait for specialist assessment, but is free on the NHS. Private access is faster (often within days) and doesn't require NHS referral, but involves paying for prescription and medication costs — typically £150–£300+ per month depending on dose.
Can I use the BMI calculator and weight loss calculator together to plan treatment?
Yes. Calculate your BMI using our free BMI calculator to check eligibility, then try our GLP-1 weight loss calculator to estimate potential results at different medication doses. These tools help you understand your starting point and set realistic expectations before discussing options with your GP or prescriber.
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.