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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Best Weights for Weight Loss in the UK
If you're looking to lose weight and wondering what options are available in the UK, prescription weight management medications may help eligible adults achieve their goals. Weight loss is most effective when combined with lifestyle changes, but for some people, medication can provide additional support. This guide explains the UK-licensed options, eligibility criteria, and how to access weight loss treatment through the NHS or privately.
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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
Three prescription-only medications are licensed in the UK specifically for weight management: Mounjaro (tirzepatide), Wegovy (semaglutide), and Saxenda (liraglutide). Both Mounjaro and Wegovy are once-weekly injections, while Saxenda is a daily injection.
Mounjaro works as a dual GIP and GLP-1 receptor agonist — activating two natural hormone pathways to help regulate appetite and support feeling fuller after meals. In clinical trials, participants lost an average of 15–21% of their body weight alongside a reduced-calorie diet and increased physical activity. Wegovy is a GLP-1 receptor agonist only, with clinical evidence showing average weight loss of around 15% of body weight at the highest dose.
Eligibility for these medications typically requires 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. For adults of South Asian, Chinese, Black African, or Black Caribbean heritage, lower BMI thresholds may apply.
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 in the UK
NHS access: NICE has approved tirzepatide (Mounjaro) for specialist weight management services, though access is through tier 3 or 4 specialist services — not standard GP prescription. Referral comes from your GP, but availability varies significantly by region and waiting times can be lengthy in some areas.
Private access: Prescription weight loss medications are available through GPhC-registered online pharmacies following a clinical assessment with a UK-licensed prescriber. This route doesn't require NHS referral and can be faster, though there is a cost involved. Either way, you'll need a prescription from a licensed healthcare professional who will assess your individual health and eligibility.
- 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 weight should I aim for to lose weight safely?
The NHS recommends losing weight at a sustainable rate of 0.5 to 1 kg (1 to 2 lbs) per week. For your personal healthy weight range, use our free BMI calculator to find the target weight band for your height — typically a BMI between 18.5 and 24.9 is considered healthy. Individual targets vary based on health conditions and personal circumstances, so speak with your GP for personalised advice.
Am I eligible for prescription weight loss medication in the UK?
You may be eligible if you have a BMI of 30 kg/m² or above, or 27–29.9 kg/m² with a weight-related health condition like type 2 diabetes or high blood pressure. Lower BMI thresholds apply for certain ethnic backgrounds. A GP or licensed prescriber will assess your individual eligibility following a clinical consultation.
How much weight can I expect to lose with Mounjaro or Wegovy?
Clinical trials showed average weight loss of 15–21% of body weight with Mounjaro and around 15% with Wegovy, achieved alongside a reduced-calorie diet and increased physical activity. However, individual results vary significantly — some people lose more, others less. Results depend on adherence, lifestyle changes, and personal metabolism. Our GLP-1 weight loss calculator can help estimate potential outcomes at different doses.
Can I get weight loss medication on the NHS?
Yes, Mounjaro (tirzepatide) is approved for NHS specialist weight management services. However, access is through tier 3 or 4 specialist services, typically via GP referral, and varies by region. Waiting lists can be lengthy. Private prescription options are also available through UK-licensed prescribers without NHS referral.
What's the difference between Mounjaro and Wegovy for weight loss?
Mounjaro (tirzepatide) is a dual GIP and GLP-1 receptor agonist offering average weight loss of 15–21%, while Wegovy (semaglutide) is a GLP-1 agonist only with average weight loss around 15%. Both are once-weekly injections. Clinical trial data suggests Mounjaro may offer slightly greater weight loss, but individual results vary. Your prescriber can discuss which is most appropriate for you.
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.