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
NHS Weight Guidance for UK Adults
The NHS provides clear guidance on healthy weight ranges and weight management support for UK adults. A healthy weight helps reduce the risk of serious health conditions including type 2 diabetes, heart disease, and certain cancers. Your GP can assess whether your current weight is healthy for you personally, taking into account your height, age, and medical history. The NHS offers support across four tiers — from self-help resources to specialist weight management services. Understanding your weight and what's healthy for you is the first step towards better health outcomes.
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.
NHS Healthy Weight Ranges and BMI Guidelines
According to NHS guidance, a healthy BMI for most UK adults is between 18.5 and 24.9. BMI (Body Mass Index) is calculated by dividing your weight in kilograms by your height in metres squared. However, if you're of South Asian, Chinese, Black African, or Black Caribbean heritage, the NHS recommends lower BMI thresholds — a healthy range of 18.5 to 22.9 — as these groups face higher health risks at the same BMI levels.
You can calculate your personal BMI instantly using our free BMI calculator above. BMI is a useful screening tool, but it has limitations — it doesn't distinguish between muscle and fat, so athletes may have a higher BMI without excess body fat. The NHS also recommends checking your waist circumference: men should aim for under 94cm (37 inches), and women under 80cm (31.5 inches).
- Underweight: BMI below 18.5
- Healthy weight: BMI 18.5–24.9
- Overweight: BMI 25.0–29.9
- Obese: BMI 30.0 and above
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 Weight Management Support — Four Tiers
The NHS provides structured weight management support across four tiers. Tier 1 includes self-help digital tools, community weight management programmes, and NHS resources like the NHS Weight Loss Plan. Tier 2 offers primary care interventions from your GP practice, including behaviour change support and monitoring.
Tier 3 is specialist multidisciplinary weight management services — referral from your GP — where prescription weight loss medications (such as GLP-1 injections) may be offered alongside diet and exercise support. Tier 4 covers bariatric surgery for severe obesity with significant health complications.
Access varies significantly by region. Your GP can advise which tier is appropriate for you and refer you to local services. Convert your weight using our free weight converter to understand where you sit in these NHS categories.
- 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 the NHS say is a healthy weight for my height?
The NHS uses BMI (Body Mass Index) to define healthy weight ranges. For most UK adults, a healthy BMI is 18.5 to 24.9. However, if you're of South Asian, Chinese, Black African, or Black Caribbean background, the NHS recommends a lower healthy range of 18.5 to 22.9 due to higher health risks at the same BMI. Your GP can calculate your personal healthy weight range based on your individual height, age, and health profile. Use our BMI calculator above for your personal BMI instantly.
How much weight should I aim to lose per week according to NHS guidance?
The NHS recommends losing weight at a steady, sustainable rate of 0.5 to 1 kg (1 to 2 lbs) per week. This typically requires a calorie deficit of around 500 calories per day. Faster weight loss is possible under medical supervision, but losing weight too quickly increases the risk of muscle loss, nutritional deficiencies, and the weight returning. Sustainable weight loss involves both reduced-calorie eating and increased physical activity.
How can I access NHS weight management services?
Start by speaking to your GP, who can assess your weight and health. If appropriate, your GP can refer you to your local NHS weight management services (tier 2 or tier 3). Tier 1 resources like the NHS Weight Loss Plan are available to anyone online. Waiting times for specialist services vary significantly by region. Your GP will advise what's available and appropriate for you. Some areas have long waiting lists, so ask about the current timescale in your area.
Does the NHS prescribe weight loss injections like Mounjaro or Wegovy?
Yes, the NHS prescribes prescription weight loss medications (GLP-1 injections such as Mounjaro and Wegovy) through specialist tier 3 weight management services. You must be referred by your GP and assessed as clinically appropriate. Eligibility typically requires a BMI of 30 or above, or 27 or above with weight-related health conditions. Availability varies significantly by region and waiting lists can be very long in many areas. Your GP can advise whether you're eligible and the current waiting time.
What if I'm below a healthy weight — is that a concern for the NHS?
Yes, being underweight (BMI below 18.5) can also affect health and requires medical assessment. Causes can include medical conditions, nutritional deficiencies, or eating disorders. If you're concerned about being underweight, speak to your GP. They can investigate the cause and provide appropriate support. Being underweight can increase risks of poor bone health, reduced immunity, and nutritional deficiencies, so it's worth discussing with your healthcare team.
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.