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
What Happens to Your Face After Weight Loss?
When you lose weight, your face often changes noticeably — cheeks may become more defined, jawlines sharper, and under-eye hollowing can occur. These facial changes are a natural part of weight loss and affect everyone differently depending on genetics, age, and how quickly weight is lost. If you're considering weight management in the UK, understanding these changes can help you feel prepared. Prescription weight loss options like Mounjaro and Wegovy are now available to eligible UK adults through both NHS specialist services and private prescribing, alongside lifestyle changes and healthy eating.
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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.
Prescription Weight Loss Options in the UK
Three main prescription weight loss medications are licensed in the UK:
- Mounjaro (tirzepatide) — a dual GIP and GLP-1 receptor agonist given as a once-weekly injection. Clinical trials showed an average weight loss of 15–21% body weight over 72 weeks at maximum doses.
- Wegovy (semaglutide) — a GLP-1 receptor agonist, also once-weekly. STEP trial data demonstrated average weight loss of approximately 15% body weight.
- Saxenda (liraglutide) — a daily GLP-1 injection, with average weight loss of around 5–10% body weight.
All three are prescription-only medicines requiring clinical assessment. You may be eligible if your BMI is 30 or above, or 27 or above with a weight-related health condition such as type 2 diabetes, high blood pressure, or sleep apnoea. Lower BMI thresholds apply if you're of South Asian, Chinese, Black African, or Caribbean heritage. Individual results vary significantly, and these medications work best alongside a reduced-calorie diet and increased physical activity. Our GLP-1 weight loss calculator can help you estimate potential outcomes at different medication doses.
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 and Next Steps
In the UK, prescription weight loss medication is available through two routes. NHS access is via specialist tier 3 weight management services — you need a GP referral, and availability varies considerably by region with sometimes lengthy waiting lists. Private access is available through GPhC-registered online prescribers following an online clinical assessment, with no NHS referral required, though there are costs involved.
If you're interested in weight management medication, start by speaking with your GP about whether you're eligible and which route suits you best. They can discuss your individual health needs, assess your BMI using our free BMI calculator, and advise on the most appropriate option. Many GPs can refer directly to NHS services, or they can guide you on private options. Remember that facial changes during weight loss are completely normal — focus on sustainable, healthy weight management rather than rapid loss.
- 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.
Will my face look different after losing weight?
Yes, facial changes are common during weight loss. Your cheeks may become more defined, your jawline sharper, and you may notice under-eye hollowing. The extent depends on genetics, age, skin elasticity, and how quickly you lose weight. These changes are natural and vary between individuals.
How do prescription weight loss medications work in the UK?
Mounjaro and Wegovy are GLP-1 or GLP-1/GIP medications that reduce appetite and help you feel fuller. They're given as once-weekly injections. Clinical trials show average weight loss of 15–21% body weight when combined with diet and exercise. Individual results vary.
Am I eligible for prescription weight loss medication on the NHS?
You may be eligible if your BMI is 30 or above, or 27 or above with a weight-related condition like diabetes or high blood pressure. Lower thresholds apply for South Asian, Chinese, Black African, or Caribbean backgrounds. Your GP can assess your individual eligibility.
What's the difference between NHS and private weight loss medication?
NHS access requires a GP referral to specialist services and varies by region, with potential waiting lists. Private access is available through online prescribers following clinical assessment, with no NHS referral needed. Both require prescription and clinical monitoring.
Can I prevent unwanted facial changes during weight loss?
You cannot prevent facial changes, but gradual weight loss (0.5–1 kg per week) may help maintain skin elasticity better than rapid loss. Staying hydrated, eating adequate protein, and maintaining skin care routines can support overall skin health during weight loss.
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.