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
NICE Guidelines for Weight Management in the UK
NICE (the National Institute for Health and Care Excellence) provides evidence-based guidance on weight management and obesity treatment used across the UK health system. These guidelines inform NHS weight loss services, GP referrals, and eligibility for prescription medications. Understanding NICE recommendations helps you know what support is available through the NHS and what healthy weight management looks like based on current evidence. Our BMI calculator can help you understand where you stand relative to NICE thresholds, while our weight converter makes it easy to check your weight in stone, pounds, or kilograms.
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.
What NICE Recommends for Weight Management
NICE guidelines recommend a structured, tiered approach to weight management in the UK:
- Tier 1: Self-help and community-based programmes — first-line support for all overweight and obese adults
- Tier 2: Specialist primary care interventions — structured behaviour change programmes, typically through GP practices
- Tier 3: Specialist weight management services — multidisciplinary teams offering intensive support, including prescription weight loss medications
- Tier 4: Bariatric surgery services — for people with severe obesity and significant health complications
NICE emphasises that weight loss of 5–10% of body weight can have meaningful health benefits, even if target weight is not reached. The organisation recommends sustainable weight loss of 0.5–1 kg per week through a combination of dietary changes, physical activity, and behaviour modification. For eligible adults, NICE has approved prescription weight loss medications — including tirzepatide (Mounjaro) and semaglutide (Wegovy) — as part of tier 3 specialist services.
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 Eligibility Criteria for Prescription Weight Loss Treatment
According to NICE guidance, prescription weight loss medications may be offered through NHS specialist services to adults with:
- A BMI of 30 kg/m² or above, OR
- A BMI of 27–29.9 kg/m² with at least one weight-related health condition (such as type 2 diabetes, high blood pressure, or cardiovascular disease)
- Lower thresholds apply for people of South Asian, Chinese, Black African, or Black Caribbean heritage — eligibility may start at BMI 27.5 or above due to higher health risks at lower weights
NICE also emphasises that medications should be used alongside lifestyle changes, not instead of them. Try our GLP-1 weight loss calculator to estimate potential outcomes with prescription medications, and use our weight converter to understand your current weight in different measurements.
- 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 NICE and why do its guidelines matter for UK weight management?
NICE (National Institute for Health and Care Excellence) is the independent organisation that provides evidence-based guidance used by the NHS. Its weight management guidelines determine what services and treatments are available on the NHS, how GPs refer patients, and which medications are approved for weight loss. Understanding NICE recommendations helps you know what support you may be eligible for.
Does NICE recommend weight loss injections like Mounjaro or Wegovy?
Yes. NICE has approved tirzepatide (Mounjaro) and semaglutide (Wegovy) as prescription-only weight loss medications for use within NHS tier 3 specialist weight management services. These are offered to eligible adults as part of a comprehensive weight management programme, always alongside lifestyle changes. Access requires referral to a specialist service and clinical assessment.
What does NICE say about healthy weight loss speed?
NICE recommends losing weight at a rate of 0.5–1 kg (approximately 1–2 lbs) per week for sustainable results. The organisation emphasises that even a 5–10% reduction in body weight — without reaching a "target weight" — can significantly improve health outcomes including blood sugar control, blood pressure, and cardiovascular health.
Can I access NICE-approved weight loss medications through my GP?
NICE-approved weight loss medications are typically available through NHS tier 3 specialist weight management services, not standard GP prescription. You usually need a referral from your GP to access these services. However, availability varies significantly by region and waiting times can be substantial. Private prescription access is also available outside the NHS.
Does NICE have different weight guidance for different ethnicities?
Yes. NICE recognises that people of South Asian, Chinese, Black African, and Black Caribbean heritage face higher health risks at lower BMI levels. The guidelines recommend lower BMI thresholds for these groups — eligibility for weight management support may start at BMI 27.5 or above, compared to 30 for other groups. This reflects evidence that excess weight carries greater health risks for these populations.
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.