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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Weight Loss Support Through UK Prescription Medication
If you're seeking weight loss support in the UK, prescription medications are now available for eligible adults alongside lifestyle changes. This guide covers the three UK-licensed options for weight management, how to check if you qualify, and the difference between NHS and private access. Whether you're exploring options or considering medication, understanding what's available is the first step toward making an informed decision with your GP.
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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 Now
Three prescription-only medications are currently licensed in the UK for weight management support. Mounjaro (tirzepatide) is a once-weekly injection that activates two natural appetite-regulating pathways — in clinical trials, participants lost an average of 15–21% of their body weight over 72 weeks. Wegovy (semaglutide) is also a once-weekly injection; clinical trials showed average weight loss of around 15% of body weight. Saxenda (liraglutide) is a daily injection option with similar clinical evidence.
- All three are prescription-only and require a clinical assessment before being prescribed
- All work best when combined with a reduced-calorie diet and increased physical activity
- Individual results vary — weight loss is not assured
- Use our GLP-1 weight loss calculator above to estimate potential outcomes at different dose levels
- All are available through NHS specialist services or private prescribing in the UK
These medications may help regulate appetite and support feeling fuller after smaller meals, making it easier to maintain a reduced-calorie diet for sustainable weight loss.
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 Prescribing — How to Find Support
NHS access: Weight loss medications are available through specialist tier 3 weight management services. You'll need a GP referral, and your local NHS health system (ICB) must have funded access — availability varies significantly across the UK. Waiting lists can be lengthy in many areas.
Private access: Available through UK-licensed prescribers following an online clinical assessment. This route does not require NHS referral and offers faster access, though you'll pay for the medication (typically £129–£320 monthly depending on dose).
Next step: Speak with your GP about whether weight loss medication might be appropriate for you. Check your BMI using our free BMI calculator above — eligibility typically starts at BMI 30 or above, or BMI 27+ with weight-related health conditions. Your prescriber will assess your individual health needs.
- 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 best weight loss medication available in the UK?
There is no single "best" medication — the right choice depends on your individual health, medical history, and how your body responds. Mounjaro, Wegovy, and Saxenda all have clinical evidence supporting weight loss. Your prescriber will assess which (if any) is most appropriate for you following a clinical assessment.
Am I eligible for NHS weight loss medication?
Generally, you may be eligible if you have a BMI of 30 or above, or a BMI of 27–29.9 with weight-related health conditions like type 2 diabetes, high blood pressure, or heart disease. South Asian, Chinese, Black African, and Black Caribbean adults may have lower thresholds. Your GP can assess your eligibility and refer you to specialist services if appropriate.
How much weight will I lose on these medications?
Clinical trials show average weight loss of 15–21% of body weight, but individual results vary significantly. Some people lose more, some less. Weight loss also depends on diet, physical activity, and other factors. Always combine medication with lifestyle changes for best results.
Can I get weight loss medication through the NHS quickly?
NHS access depends on your local area and current waiting lists. Many areas have significant waiting times (months to years in some regions). If you need faster access, private prescribing is available, though it is not free. Ask your GP about both options.
Do weight loss medications work without diet and exercise changes?
Prescription weight loss medications are most effective when combined with a reduced-calorie diet and increased physical activity. Medication alone is unlikely to produce sustained results. These drugs support lifestyle changes — they do not replace them.
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.