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 Causes Extra Skin After Weight Loss?
When you lose a significant amount of weight — whether through dietary changes, increased physical activity, or prescription weight loss medication — your skin may not always shrink back completely. This loose or extra skin can affect your body contour and confidence. Understanding why this happens, how much it matters, and what options are available can help you make informed decisions about your weight loss journey and realistic expectations for your results.
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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 Extra Skin Develop After Weight Loss?
Your skin contains elastic fibres (collagen and elastin) that stretch as you gain weight over time. When you lose weight rapidly, your skin has less time to adapt and gradually contract back. Several factors affect how much extra skin you'll develop:
- Speed of weight loss — Rapid loss means skin has less time to shrink naturally; gradual loss allows more skin contraction
- Age — Younger skin has better elasticity; older skin is less able to bounce back
- Starting BMI — People who were at very high weights may have more noticeable loose skin
- Duration of obesity — Skin stretched over many years may be more permanently affected
- Genetics — Some people naturally have better skin elasticity than others
- Hydration and nutrition — Adequate protein and hydration support skin health during weight loss
Weight loss medication like GLP-1 weight loss injections may result in significant weight loss, which is why understanding skin changes is important when considering this prescription weight loss option in the UK.
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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 Extra Skin and What to Expect
Many people find that some loose skin gradually improves over 12–18 months as collagen remodels, especially with younger skin and slower weight loss. You can support skin health during weight management by maintaining adequate protein intake, staying hydrated, using moisturiser, and protecting skin from sun damage. If loose skin causes physical discomfort or significant distress, your GP can discuss options including dermatology referral or, in some cases, plastic surgery (though this is rarely available on the NHS for cosmetic loose skin unless it's causing medical problems).
Track your weight loss progress and overall health using our free progress tracker. Remember that health improvements from weight loss — better blood pressure, improved blood sugar control, reduced joint pain — often matter far more than minor skin changes. Use our BMI calculator to understand your current health status and set realistic, healthy weight loss targets with your GP or prescriber.
- 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 tighten up after weight loss?
Some skin tightening does occur naturally over 12–18 months as collagen remodels. Younger people and those who lose weight gradually typically see better skin contraction. However, if you've lost a very large amount of weight, some loose skin may remain permanently. Using moisturiser, staying hydrated, and getting adequate protein can support skin health during the process.
How much loose skin should I expect after weight loss?
This varies widely depending on your age, genetics, how much weight you've lost, and how quickly you lost it. Someone losing 5–10kg may see minimal loose skin, whilst someone losing 30kg or more may notice more noticeable changes. Your GP or a dermatologist can assess your individual situation if you're concerned.
Does weight loss medication like Wegovy cause more loose skin?
GLP-1 medications like Wegovy can result in significant weight loss — clinical trials showed average losses of around 15% body weight. Faster weight loss can mean less time for skin to adapt. However, loose skin is a normal part of any substantial weight loss. Talk to your prescriber about realistic expectations before starting prescription weight loss treatment.
What can I do to prevent or reduce loose skin during weight loss?
Whilst you can't completely prevent loose skin with significant loss, you can support skin health by: losing weight gradually (0.5–1kg per week), eating adequate protein, staying well hydrated, using moisturiser regularly, exercising (which may help with skin tightness), and protecting skin from sun damage. These steps support overall health too.
Can the NHS help with loose skin after weight loss?
Your GP can refer you to a dermatologist if loose skin is causing medical problems (like skin irritation or infection in skin folds). Cosmetic surgical removal of excess skin is rarely available on the NHS unless there's a medical need. Private cosmetic procedures exist but are not covered by the NHS and carry their own risks.
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.