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
Start Your Weight Loss Journey — UK Medication Options
Your weight loss journey can include prescription medication alongside lifestyle changes if you're eligible in the UK. Several evidence-based options are now available through the NHS and private prescribing, including GLP-1 receptor agonists like Mounjaro and Wegovy. Understanding what's available, who qualifies, and how to access support is the first step toward sustainable weight management. Our free BMI calculator can help you understand your starting point and eligibility for prescription options.
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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 Weight Loss Medications Available
Three prescription-only medications are licensed for weight management in the UK. Mounjaro (tirzepatide) is a dual GIP and GLP-1 receptor agonist — a once-weekly injection that works on two natural hormone pathways to help reduce appetite and support feeling fuller. Wegovy (semaglutide) is a GLP-1 receptor agonist, also injected once weekly, approved for weight loss across the UK. Saxenda (liraglutide) is a daily GLP-1 injection option, though less commonly prescribed.
Clinical trials show Mounjaro helped participants lose an average of 15–21% of their body weight, whilst Wegovy showed approximately 15% average weight loss — though individual results vary significantly. These prescription weight loss medications work best alongside a reduced-calorie diet and increased physical activity. Eligibility depends on your BMI and health conditions. Adults with a BMI of 30 kg/m² or above may qualify, or those with a BMI of 27–29.9 kg/m² with weight-related health conditions such as type 2 diabetes, high blood pressure, or sleep apnoea.
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 — How to Get Started
NHS access: Weight loss medications are available through tier 3 specialist weight management services. Your GP can refer you to your local service, though waiting lists vary significantly by region and availability can be limited. Some areas have shorter waiting times, whilst others have extended delays of several months.
Private access: You can access GLP-1 medications through private UK prescribers following an online clinical assessment with a GPhC-registered pharmacy. This route bypasses NHS waiting lists but involves private costs (typically £129–£320 monthly depending on dose).
To explore your options, use our free BMI calculator to check your starting point, then speak with your GP about NHS eligibility or contact a private prescriber. Your weight management journey deserves professional support from the start.
- 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 BMI do I need for weight loss medication in the UK?
Adults with a BMI of 30 or above, or 27–29.9 with weight-related health conditions, may qualify. If you're of South Asian, Black African, or Chinese heritage, lower thresholds apply. Use our free BMI calculator to check your starting point and discuss eligibility with your GP or a licensed prescriber.
How much weight can I expect to lose with Mounjaro or Wegovy?
Clinical trials show average weight loss of 15–21% with Mounjaro and approximately 15% with Wegovy. However, individual results vary significantly based on diet, activity, and personal factors. These medications work best alongside a reduced-calorie diet and increased physical activity. Results are not assured.
Can I access weight loss medication through the NHS?
Yes, through tier 3 specialist weight management services. Your GP can refer you, but waiting lists vary by region. Some areas offer faster access than others. If you prefer immediate access, private prescribing is available following a clinical assessment. NHS access is typically free at point of use once approved.
What's the difference between Mounjaro and Wegovy?
Mounjaro (tirzepatide) is a dual GIP and GLP-1 agonist, whilst Wegovy (semaglutide) is a GLP-1 agonist only. Both are once-weekly injections. Mounjaro showed slightly higher average weight loss (15–21%) compared to Wegovy (approximately 15%) in clinical trials, but individual response varies. A prescriber will advise which is appropriate for you.
Do I need to change my diet and exercise while taking weight loss medication?
Yes. Prescription weight loss medications work best alongside a reduced-calorie diet and increased physical activity. The medications help by reducing appetite and supporting fullness, but lifestyle changes remain essential for sustainable results. Your GP or weight management service can provide support with diet and exercise planning alongside medication.
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.