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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Managing Excess Skin After Weight Loss Surgery in the UK
After significant weight loss following bariatric surgery, excess skin is a common physical concern that affects many adults in the UK. While this loose skin poses no direct health risk, some people choose to address it through additional surgical procedures or explore ongoing weight management strategies. Understanding your options — including prescription weight management medications available through the NHS and private services — can help you make informed decisions about your health moving forward.
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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.
UK Prescription Weight Management Options After Bariatric Surgery
For adults who have undergone weight loss surgery and wish to maintain or continue their weight loss, several prescription weight management medications are now available in the UK. These are licensed for eligible adults and may support ongoing weight control.
Mounjaro (tirzepatide) is a once-weekly injectable medication that works by activating two natural hormone pathways, helping to regulate appetite and support feeling fuller after meals. Wegovy (semaglutide) is another once-weekly GLP-1 injection licensed for weight management. Saxenda (liraglutide) is a daily injection option also available in the UK.
These medications are prescription-only and require a clinical assessment before being prescribed. You may be eligible if you have a BMI of 30 or above, or 27–29.9 with weight-related health conditions such as type 2 diabetes, high blood pressure, or cardiovascular disease. Eligibility is assessed individually by a prescriber based on your personal health profile and medical history.
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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.
Accessing Weight Management Support: NHS and Private Routes
NHS route: Weight management medications may be available through NHS specialist tier 3 services. Your GP can refer you to your local weight management service, though availability and waiting times vary significantly across UK regions. Ask your GP about current provision in your area.
Private route: Prescription weight management medications are also available through GPhC-registered online pharmacies following an online clinical assessment with a UK-licensed prescriber. This route does not require an NHS referral and is typically faster to access, though costs are met privately.
Whichever route you choose, a healthcare professional will assess whether prescription medication is suitable for your individual circumstances. You can use our free BMI calculator to understand your current weight category and discuss this with your GP to explore which option might be right for you.
- 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 weight management medication help prevent excess skin after weight loss?
Prescription weight management medications support gradual, sustained weight loss. Slower weight loss may allow skin to adapt better, potentially reducing excess skin formation. However, medications cannot prevent loose skin entirely — genetics, age, and the amount of weight lost all influence skin elasticity. Your GP can advise on realistic expectations for your situation.
Can I take weight management medication if I've had bariatric surgery?
This depends on the type of bariatric surgery you've had and your individual health. Some weight loss medications may not be suitable after certain procedures due to absorption issues. Your prescriber will assess your medical history and surgery type before determining eligibility. Always inform them of your bariatric surgery.
How long do I need to take prescription weight management medication?
Weight management medications are typically prescribed on an ongoing basis for continued benefit. Your prescriber will monitor your progress and discuss long-term use with you. If you stop taking the medication, weight loss may not be sustained, so ongoing use is usually recommended for continued weight management.
What's the difference between Mounjaro and Wegovy for weight management?
Mounjaro (tirzepatide) activates two hormone pathways (GIP and GLP-1), while Wegovy (semaglutide) activates one (GLP-1 alone). Clinical trials show both support significant weight loss when combined with lifestyle changes. Your prescriber will assess which is more appropriate for your individual needs and medical history.
How can my GP help me decide if weight management medication is right for me?
Your GP can assess your current BMI using our free BMI calculator, review your weight-related health conditions, discuss your weight loss goals, and explain whether you meet eligibility criteria for prescription treatment. They can refer you to NHS services or advise on private options. Book an appointment to have an honest conversation about your concerns.
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.