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 is Excess Skin After Weight Loss?
Excess skin, or loose skin, can develop after significant weight loss. When you lose a large amount of weight—whether through diet, exercise, or prescription weight loss medication like Wegovy or Mounjaro—your skin may not contract fully to fit your new body shape. This is a natural physiological response, not a failure, and understanding why it happens can help you make informed decisions about weight management in the UK.
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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 Does Loose Skin Develop After Weight Loss?
Excess skin develops because your skin loses elasticity over time. When you carry excess weight, your skin stretches to accommodate your body. As you lose weight—especially rapid loss through prescription weight loss medication or intensive diet changes—your skin may not have enough elasticity to shrink back completely.
Key factors affecting loose skin include:
- Amount of weight lost (larger losses increase risk)
- Speed of weight loss (faster loss leaves less time for skin to adapt)
- Age (younger skin has better elasticity)
- Starting BMI (people with higher BMI may experience more loose skin)
- Genetics (some people naturally have more elastic skin)
- Duration of obesity (long-term excess weight reduces skin elasticity permanently)
- Hydration and nutrition during weight loss
Clinical trials of weight management medications like those used in GLP-1 weight loss programmes show that average weight loss ranges from 15–21% of body weight, which can be significant enough to trigger loose skin in some people.
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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.
Prevention and Management Strategies
While you cannot assures prevention of excess skin, several evidence-based strategies may help minimise it:
- Lose weight gradually — aim for 0.5–1 kg per week (the NHS-recommended rate) to allow skin time to adapt
- Build muscle through exercise — strength training can fill space under skin and improve appearance
- Stay hydrated — drink adequate water daily to support skin health
- Maintain good nutrition — ensure adequate protein and micronutrients for skin elasticity
- Moisturise skin regularly — may help with appearance though it will not remove loose skin
- Use our free progress tracker — monitor your weight loss speed to ensure you're losing at a sustainable rate alongside lifestyle changes
If you're considering prescription weight loss medication, your prescriber will discuss the potential for loose skin as part of your treatment plan.
- 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 everyone develop excess skin after weight loss?
No. Excess skin depends on many factors including genetics, age, how much weight you lose, and how quickly. Younger people and those losing smaller amounts of weight are less likely to develop noticeable loose skin. Your GP or prescriber can discuss your individual risk.
Can I prevent excess skin with weight loss medication like Wegovy?
Wegovy (semaglutide) is a prescription GLP-1 weight loss injection licensed in the UK. While it may support significant weight loss, no medication prevents loose skin entirely. Combining weight loss with strength training and gradual loss may help minimise it.
Is excess skin after weight loss dangerous to my health?
Loose skin is not medically dangerous, though it may occasionally cause skin irritation in folds. The health benefits of weight loss typically far outweigh concerns about loose skin. Your GP can advise on any skin-related concerns.
What NHS support is available for loose skin in the UK?
The NHS focuses on weight management and health outcomes rather than cosmetic concerns. If loose skin causes functional problems or skin infection, your GP can assess you. Cosmetic surgery for loose skin is rarely available on the NHS unless medically necessary.
Should I avoid weight loss medication because of excess skin risk?
No. The health benefits of weight loss—reduced diabetes risk, lower blood pressure, improved joint health—far outweigh cosmetic concerns about loose skin. Discuss any concerns with your GP or prescriber before starting any weight management programme.
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.