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
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Free Weight Loss Tracker and UK Prescription Options
A free weight loss tracker helps you monitor your progress, but many UK adults also benefit from prescription medication to support sustainable weight management. If you're carrying excess weight and struggling with diet and exercise alone, prescription options like Mounjaro and Wegovy are available through the NHS or privately following a clinical assessment. This guide covers what you need to know about UK-licensed weight loss medication, eligibility criteria, and how to get started. Track your progress using our free progress tracker while exploring all available support options for effective weight management.
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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 medications are currently licensed in the UK for weight management:
- Mounjaro (tirzepatide) — a once-weekly injection that activates dual GIP and GLP-1 pathways. Clinical trials showed an average weight loss of 15–21% of body weight over 72 weeks, alongside reduced-calorie diet and increased physical activity.
- Wegovy (semaglutide) — a once-weekly GLP-1 injection. STEP trial data demonstrated average weight loss of approximately 15% of body weight at 68 weeks.
- Saxenda (liraglutide) — a once-daily GLP-1 injection, with similar efficacy to Wegovy.
All three are prescription-only medicines and require a clinical assessment to confirm eligibility. Individual results vary significantly based on lifestyle changes, genetics, and adherence. Eligibility criteria: adults with a BMI of 30 or above, or BMI of 27–29.9 with at least one weight-related health condition (type 2 diabetes, high blood pressure, sleep apnoea, or cardiovascular disease). Lower thresholds apply for adults of South Asian, Chinese, Black African, or Black Caribbean heritage due to higher health risks at lower BMI levels.
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 Access vs Private Options in the UK
In the UK, prescription weight loss medication is accessed through two pathways. NHS route: referral to a tier 3 specialist weight management service from your GP, with assessment and prescription through the service. Availability varies significantly by region and waiting times can be substantial — some areas have waiting lists of several months to years. Private route: online consultation with a UK-licensed prescriber, with prescription dispensed by a GPhC-registered pharmacy if clinically suitable. No NHS referral required, though costs typically range from £129–£320 per month depending on dose.
Either pathway requires lifestyle changes alongside medication. Speak to your GP first to discuss whether prescription weight loss support is appropriate for you and to understand local NHS options. Our free progress tracker helps you monitor results whether you choose medication or lifestyle changes alone.
- 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's the difference between Mounjaro and Wegovy?
Both are once-weekly injections for weight management, but Mounjaro is a dual GIP + GLP-1 agonist while Wegovy is GLP-1 only. Clinical trials suggest Mounjaro may offer slightly greater average weight loss (15–21% vs approximately 15%), though individual results vary. Both require prescription and clinical assessment. Ask your prescriber which is more suitable for your situation.
Can I access weight loss medication through the NHS?
Yes, through specialist tier 3 weight management services. You'll need a GP referral and assessment by the specialist service. Availability and waiting times vary significantly by region — contact your local integrated care board (ICB) for information. Many areas have substantial waiting lists, so private options may be faster if you meet eligibility criteria.
What eligibility criteria apply for prescription weight loss medication in the UK?
Adults with a BMI of 30 or above, or BMI of 27–29.9 with weight-related health conditions (type 2 diabetes, hypertension, sleep apnoea, cardiovascular disease) may be eligible. Lower thresholds apply for South Asian, Chinese, Black African, or Black Caribbean adults due to higher health risks. A prescriber will assess your individual circumstances and health history.
How can I track my weight loss progress?
Use our free progress tracker to log your weight regularly and visualise your journey over time. Combine this with the BMI calculator to monitor changes in your health metrics. Regular tracking helps identify trends, maintains motivation, and provides data to discuss with your GP or prescriber about medication effectiveness.
Do weight loss medications work without diet and exercise changes?
No. Prescription weight loss medications are most effective when combined with reduced-calorie diet and increased physical activity. They support appetite control and help you feel fuller after meals, making lifestyle changes easier to maintain. The NHS recommends a calorie deficit of around 500 kcal per day for sustainable loss of approximately 0.5 kg per week.
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.