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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Saggy Bottom After Weight Loss — What You Need to Know
Loose or saggy skin after significant weight loss is a common concern for many UK adults, especially after rapid weight management. This happens because skin loses elasticity as it stretches during weight gain, and when you lose weight quickly — whether through diet, exercise, or weight management medication like GLP-1 injections — the skin doesn't always tighten immediately. Understanding why this occurs and what options are available can help you make informed decisions about your weight management 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 Does Skin Become Saggy After Weight Loss?
When you carry excess weight, your skin stretches over months or years to accommodate the larger body. The skin contains collagen and elastin fibres that provide structure and elasticity. As these fibres stretch, they can lose some ability to bounce back, especially if weight gain was rapid or prolonged.
Several factors affect how much loose skin you may experience after weight loss:
- Speed of weight loss — gradual weight management (over 1 kg per week) gives skin less time to adapt and retract
- Age — younger skin generally has better elasticity; skin loses collagen production naturally with age
- Genetics — some people's skin is naturally more elastic than others
- Amount of weight lost — losing 20% or more of body weight makes loose skin more noticeable
- Duration of obesity — skin stretched over many years may have less recovery potential
- Smoking and sun damage — both reduce skin elasticity
If you're using GLP-1 weight loss medication like Mounjaro or Wegovy, weight loss typically occurs over months, which may allow more time for skin adaptation compared to very gradual weight management methods.
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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 Loose Skin — Practical Options
For most people, loose skin does improve naturally over 12–24 months as collagen remodelling occurs and skin gradually tightens. Staying hydrated, maintaining a balanced diet rich in protein, and doing resistance exercises can support skin health during this period. Our free progress tracker can help you monitor your overall weight loss journey alongside skin changes.
If loose skin persists or significantly affects your wellbeing, options include cosmetic procedures — though these are private treatments not typically available on the NHS. Your GP can discuss your concerns and may refer you to a dermatologist. Avoid gradual weight management in future by maintaining a sustainable weight management approach with your GP or a qualified healthcare professional, including using evidence-based tools like our free BMI calculator and GLP-1 weight loss calculator to plan realistic targets.
- 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 loose skin tighten up on its own after weight loss?
Yes, in many cases. Most loose skin improves over 12–24 months as collagen rebuilds and skin gradually contracts. The timeline varies based on age, genetics, and how much weight you lost. Younger people typically see faster improvement. Staying hydrated and eating adequate protein can support this natural process.
How can I prevent saggy skin during weight loss?
Lose weight at a sustainable rate (0.5–1 kg per week recommended by the NHS) rather than very rapidly. This gives your skin time to adjust gradually. Build muscle through resistance exercise, stay hydrated, eat protein-rich foods, and avoid smoking. Using structured weight management — whether through diet or prescription medication — helps control the pace of loss.
Are there medical treatments for loose skin after weight loss?
The NHS rarely offers surgical skin removal for loose skin resulting from weight loss alone. Private cosmetic procedures exist (skin tightening, surgical removal) but these are not NHS-funded and require consultation with a private cosmetic surgeon. Your GP can discuss your options and any underlying health concerns.
Does loose skin affect your BMI or health measurements?
Loose skin doesn't change your actual BMI or body weight — it's still counted in your total weight. However, excess loose skin can affect comfort and confidence. Our free BMI calculator shows your current health classification, and your GP can assess whether loose skin poses any health risks specific to you.
Does weight loss medication like Wegovy cause more loose skin?
GLP-1 medications like Wegovy cause weight loss over weeks and months, allowing more gradual skin adaptation than very rapid dieting. Clinical trials showed weight loss of around 14–15% over 68 weeks. Gradual weight management typically results in less severe loose skin compared to crash dieting, though individual results vary and genetics play a major role.
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.