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 During Weight Loss in the UK
Excess skin is a natural consequence of significant weight loss, particularly when losing weight rapidly or over a large amount. While prescription weight management medications like Mounjaro and Wegovy can support weight loss in eligible UK adults, understanding how these options work alongside healthy skin management is important. This guide covers NHS-licensed weight loss medication available in the UK, eligibility criteria, and how to discuss options with your GP.
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Calculate Your BMI Instantly
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-Licensed Weight Loss Medications and Eligibility
Three prescription-only medications are currently licensed in the UK for weight management:
- Mounjaro (tirzepatide) — dual GIP and GLP-1 receptor agonist, once-weekly injection. Clinical trials showed average weight loss of 15–21% body weight at maximum dose over 72 weeks, alongside a reduced-calorie diet and increased physical activity.
- Wegovy (semaglutide) — GLP-1 receptor agonist, once-weekly injection. Average weight loss was approximately 15% body weight in clinical trials at 68 weeks on the maximum 2.4 mg dose.
- Saxenda (liraglutide) — GLP-1 receptor agonist, once-daily injection. Weight loss comparable to Wegovy, though less commonly prescribed in the UK than once-weekly options.
You may be eligible if your BMI is 30 or above, or 27–29.9 with a weight-related health condition such as type 2 diabetes, hypertension, or cardiovascular disease. Lower BMI thresholds apply if you're of South Asian, Chinese, Black African, or Black Caribbean heritage. Use our free BMI calculator to check your personal BMI and assess potential eligibility.
Clinically BackedWeight Loss
No appointments. No waiting rooms. Just care — from a UK-regulated online pharmacy.
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.
NHS vs Private Access and Next Steps
In the UK, weight loss medication is available through two routes. NHS access: Referral to a tier 3 specialist weight management service through your GP. Availability and waiting times vary significantly by region. Private access: Online consultation with a UK-licensed prescriber through GPhC-registered pharmacies — no NHS referral required, though costs apply (typically £129–£320 per month depending on dose).
Start a conversation with your GP about whether prescription weight management is appropriate for you. They can assess your individual health, discuss potential side effects (commonly nausea, diarrhoea, and constipation), and consider whether medication aligns with your weight loss goals. Medications work best alongside a reduced-calorie diet, increased physical activity, and sustainable lifestyle changes. Track your progress with our free weight loss progress tracker as you work towards your goals.
- 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 loss medication prevent excess skin after weight loss?
No. Excess skin is a natural result of significant weight loss, particularly rapid loss. While prescription weight loss medications support gradual, sustained weight loss (which may reduce skin laxity compared to very rapid loss), they don't prevent loose skin entirely. Gradual loss, strength training, and adequate hydration may help, but dermatological options exist if loose skin becomes a concern after weight loss.
What's the difference between Mounjaro and Wegovy for weight loss?
Mounjaro (tirzepatide) is a dual GIP and GLP-1 agonist; Wegovy (semaglutide) is a GLP-1 agonist only. Mounjaro showed slightly higher average weight loss in clinical trials (15–21% vs approximately 15%), but individual results vary significantly. Both are once-weekly injections. Your GP or prescriber will advise which is more suitable for you.
How long does it take to see weight loss results with these medications?
Weight loss typically begins within weeks, though individual timelines vary. Most people notice meaningful results within 8–12 weeks on a stable dose. Clinical trials measured outcomes at 68–72 weeks. These medications work best as part of a sustained approach combining dietary changes, physical activity, and lifestyle support.
Can I get weight loss medication through the NHS without a long wait?
NHS availability for specialist weight management services varies by region and current demand. Many areas have significant waiting lists (months to years). Private routes offer faster access following an online clinical assessment. Discuss both options with your GP to understand what's available in your area.
What happens to excess skin if I lose weight slowly with medication?
Gradual weight loss (0.5–1 kg per week) may allow skin to adapt better than rapid loss, potentially reducing loose skin. However, significant weight loss typically results in some degree of skin laxity regardless of pace. Strength training, adequate hydration, and sun protection may help skin elasticity. Dermatological treatments exist if loose skin becomes a concern.
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.