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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Does Skin Shrink After Weight Loss?
Yes, skin does typically shrink after weight loss, though the extent varies significantly between individuals. When you lose weight through diet, exercise, or prescription weight management medications like Mounjaro or Wegovy, your skin gradually adapts to your smaller body size. However, the speed and completeness of this adaptation depend on factors including how much weight you've lost, your age, genetics, and the timeline over which you lost the weight. This guide explains what happens to your skin during weight loss and how prescription options available for UK weight management might affect this process.
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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.
How Skin Adapts During Weight Loss
Skin is elastic and contains collagen and elastin fibres that allow it to stretch and contract. During significant weight loss, these fibres gradually retract, causing your skin to conform to your new body shape. This process typically takes several months to years depending on the amount of weight lost.
Key factors affecting skin retraction include:
- Speed of weight loss: Gradual loss (0.5–1 kg per week, as recommended by the NHS) generally allows better skin adaptation than rapid loss
- Age: Younger skin has greater elasticity and adapts more efficiently
- Total weight lost: Losses of 10–15 kg often result in good skin retraction; larger losses (25+ kg) may leave some loose skin
- Genetics: Skin elasticity is partly inherited and varies between individuals
- Hydration and nutrition: Adequate protein and water support skin health during weight loss
When using prescription weight loss medications like GLP-1 injections for weight management in the UK, the gradual nature of typical weight loss supports natural skin adaptation and may help minimise excess loose skin compared to very gradual weight management.
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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
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Prescription Weight Loss Options in the UK
For adults eligible for prescription weight management in the UK, three main options are available: Mounjaro (tirzepatide), Wegovy (semaglutide), and Saxenda (liraglutide). These medications support gradual weight loss alongside diet and increased physical activity, which may help your skin adapt more naturally than crash dieting.
UK eligibility typically requires a BMI of 30 or above, or 27 or above with weight-related health conditions. Access through the NHS is via specialist weight management services, though waiting lists vary by region. Private access is available through UK-licensed prescribers following an online clinical assessment.
Use our free GLP-1 weight loss calculator to explore potential weight loss outcomes with prescription medication, and our BMI calculator to check your starting point. Your GP can advise whether prescription weight loss treatment is suitable for you and discuss which option may be most appropriate for 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.
Will my skin definitely shrink back after weight loss?
Most people experience significant skin retraction after weight loss, but the degree varies. Gradual weight loss, good hydration, adequate protein intake, and younger age all support better skin adaptation. Losses of 10–15 kg typically result in good retraction; larger losses may leave some loose skin that doesn't fully retract, especially in the stomach, arms, or thighs.
How long does it take for skin to shrink after weight loss?
Skin retraction is a gradual process typically taking 3–12 months for noticeable results, with continued improvement over 1–2 years. The timeline depends on the amount of weight lost, your age, genetics, and how quickly you lost the weight. Slower, sustainable weight loss (around 0.5–1 kg per week as recommended by the NHS) generally allows better skin adaptation.
Does losing weight through prescription medication affect skin differently?
Prescription weight loss medications like Mounjaro and Wegovy support gradual weight loss alongside lifestyle changes, which may help skin adapt naturally. The typical weight loss achieved over weeks and months gives your skin time to retract, potentially resulting in less excess loose skin compared to very gradual weight management from extreme calorie restriction.
What can I do to help my skin shrink during weight loss?
Stay hydrated (drink plenty of water), eat adequate protein (supports skin elasticity), use moisturiser regularly, avoid smoking, and manage weight loss gradually at 0.5–1 kg per week rather than rapid loss. Strength training can also help by building muscle under the skin, creating a firmer appearance as you lose fat.
When should I consider talking to my GP about prescription weight management?
If you have a BMI of 30 or above, or 27 or above with health conditions like type 2 diabetes or high blood pressure, your GP can discuss weight management options including prescription medications, behaviour change programmes, or referral to specialist NHS services. A GP assessment helps ensure any weight loss approach is safe and appropriate for your individual health.
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.