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
Weight Loss Programs in the UK — What Works
A weight loss program combines dietary changes, increased physical activity, and sometimes medical support to help you reach a healthier weight. In the UK, you have several options available—from free NHS resources to prescription weight loss medication through specialist services or private prescribers. The most effective approach depends on your individual circumstances, health conditions, and BMI. Our free BMI calculator can help you understand where you currently stand, while our GLP-1 weight loss calculator may help you explore potential outcomes if prescription medication is an option for you.
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 Weight Management Pathways and Options
The NHS offers a structured approach to weight management called the tiered pathway. Tier 1 includes self-help tools, digital programmes, and community weight loss groups—many available free through your local NHS. Tier 2 involves primary care support where your GP may recommend behaviour change programmes like the NHS Weight Loss Plan. Tier 3 is specialist multidisciplinary weight management services, where prescription weight loss medication may be considered. Tier 4 is bariatric surgery for severe obesity with significant health complications.
For sustainable weight loss in the UK, the NHS recommends losing 0.5 to 1 kg per week alongside a reduced-calorie diet and increased physical activity. A calorie deficit of approximately 500 kcal per day typically supports this rate. You can access free support through your GP, local weight management services, or online resources—no referral needed for many community programmes. Try our free progress tracker to log your weight journey and monitor changes over time.
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.
Prescription Weight Loss Options and GLP-1 Medication
Prescription weight loss medication is available through the NHS specialist tier 3 services or privately through licensed UK prescribers. Currently, two main GLP-1 medications are licensed for weight management: Mounjaro (tirzepatide) and Wegovy (semaglutide). Both are once-weekly injections that may help reduce appetite and support weight loss alongside lifestyle changes. In clinical trials, Wegovy helped participants lose an average of approximately 15% of body weight, though results vary individually. Access through the NHS involves referral to specialist services, which may have waiting lists. Private prescribing requires an online clinical assessment with a licensed UK prescriber. Use our GLP-1 weight loss calculator to explore potential outcomes at different doses if you're considering prescription options.
- 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 the safest rate of weight loss?
The NHS recommends losing 0.5 to 1 kg (1 to 2 lbs) per week for sustainable results. This typically requires a calorie deficit of around 500 kcal per day. Very gradual weight management (more than 1.5 kg per week) increases muscle loss risk and should only be attempted under medical supervision. Aim for gradual, consistent progress rather than dramatic short-term drops.
Can I access weight loss medication through the NHS?
Yes. Prescription weight loss medications like Mounjaro and Wegovy are available through NHS specialist tier 3 weight management services. You'll need a referral from your GP, and eligibility is based on BMI and health conditions. Availability and waiting times vary significantly by region. Private prescribing is also available through licensed UK prescribers without NHS referral.
What BMI qualifies me for prescription weight loss treatment?
Adults with a BMI of 30 or above, or 27 or above with weight-related health conditions (such as type 2 diabetes, high blood pressure, or cardiovascular disease), may be eligible. For South Asian, Chinese, Black African, or Black Caribbean adults, lower BMI thresholds may apply. A GP or licensed prescriber can assess your individual eligibility.
Are weight loss injections the only option?
No. Weight loss injections are one tool among many. Effective approaches include dietary changes (Mediterranean diet, calorie deficit), increased physical activity, behaviour change programmes, and structured support through NHS or community services. Medication works best alongside lifestyle changes, not instead of them. Many people achieve successful weight loss through lifestyle adjustments alone.
How do I track my weight loss progress?
Our free progress tracker allows you to log your weight, monitor changes over time, and see your progress visually. Weekly or fortnightly logging helps identify trends. Use our weight converter to switch between kg, stone, and pounds if you prefer. Tracking also supports motivation and helps you and your GP assess whether your current approach is working.
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.