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 through weight management or prescription medications like GLP-1 injections, your face is often one of the first and most noticeable areas to change. This happens because facial fat decreases as your body uses stored energy, and the skin around your face may become looser or more defined. Understanding these changes — and how to support your skin during weight loss — helps you feel confident about your appearance throughout your weight loss journey.
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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.
Why Facial Changes Occur During Weight Loss
Your face contains a layer of subcutaneous fat beneath the skin that gives it fullness and volume. When you lose weight through a reduced-calorie diet, increased physical activity, or prescription weight management medications (such as Wegovy, Mounjaro, or other GLP-1 medications), your body burns stored fat reserves — including facial fat — for energy.
The rate and extent of facial changes depends on several factors: how much weight you lose overall, your starting BMI, your age, genetics, and your skin's elasticity. Some people notice facial definition appearing within the first few weeks of weight loss, whilst others experience more gradual changes over several months.
In clinical trials of GLP-1 weight loss medications, participants lost an average of 14–21% of their body weight, and facial changes were commonly reported alongside this weight loss. Your BMI also matters — use our free BMI calculator to understand your current weight category and set realistic expectations for changes ahead.
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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.
Managing Skin Health During Weight Loss
gradual weight management can sometimes leave skin loose or less elastic, particularly if you lose a large amount of weight quickly. To support your skin during weight loss:
- Stay hydrated — aim for 6–8 glasses of water daily to maintain skin elasticity
- Eat protein-rich foods — protein supports skin structure and collagen production
- Use sunscreen daily — UV damage becomes more visible as facial fat decreases
- Moisturise regularly — hydrated skin appears fuller and more supple
- Be patient — skin can take months to adapt after significant weight loss
- Consult your GP — they can advise on skin concerns or refer you to a dermatologist if needed
Track your weight loss progress using our free progress tracker to monitor changes over time. This helps you see the full picture of your health improvement, not just facial appearance.
- 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.
Does your face get thinner when you lose weight?
Yes. As you lose weight, subcutaneous fat in your face decreases, making cheekbones more prominent, jawlines more defined, and overall facial features more angular. The timeline varies — some people notice changes within 4–6 weeks, others take 3–4 months.
Can GLP-1 medications like Wegovy cause facial changes?
Wegovy and other GLP-1 medications support weight loss alongside diet and exercise. Clinical trials showed participants lost 14–21% of body weight on average, which naturally includes facial fat loss. Facial changes are a result of weight loss itself, not the medication directly.
Will my face look loose or saggy after weight loss?
This depends on how much weight you lose, how quickly, your age, and genetics. Skin has elasticity that can recover, especially over 12 months post-weight loss. Staying hydrated, using moisturiser, eating protein, and exercising (which builds muscle) can all help skin appearance during weight loss.
How can I improve my skin during weight loss?
Hydrate well, eat sufficient protein, use daily sunscreen, moisturise regularly, and avoid gradual weight management (the NHS recommends 0.5–1 kg per week for sustainable results). Your GP can also advise on skincare or refer you to a dermatologist if you have specific concerns.
Is facial weight loss permanent?
Once fat cells are used for energy, they don't return unless you regain weight. However, skin can adjust and improve over time. Maintaining a stable healthy weight through balanced diet and exercise helps keep your results sustainable. Use our BMI calculator to understand your healthy weight range.
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.