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
Can Collagen Help With Weight Loss?
Collagen is a popular supplement marketed for skin, joints, and metabolism support, but evidence for weight loss is limited. While collagen may support muscle maintenance during weight loss, it is not a weight loss medication. If you're looking for clinical evidence-backed options for weight management in the UK, prescription medications are available for eligible adults. Our free GLP-1 weight loss calculator can help you understand what evidence-based options might look like with medical support.
10,000+ calculations today · NHS-aligned thresholds · 100% free
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 Prescription Weight Loss Options
If you're interested in medically-supervised weight management in the UK, three prescription medications are currently licensed and approved by the MHRA:
- Mounjaro (tirzepatide) — a dual GIP and GLP-1 receptor agonist, given once weekly. Clinical trials showed participants lost an average of 15–21% of their body weight over 72 weeks, though individual results vary significantly.
- Wegovy (semaglutide) — a GLP-1 receptor agonist, given once weekly. STEP trial data showed an average weight loss of approximately 15% of body weight at 68 weeks, alongside a reduced-calorie diet and increased physical activity.
- Saxenda (liraglutide) — a GLP-1 receptor agonist, given as a daily injection. Evidence supports modest weight loss outcomes, typically around 5–10% of body weight.
These are prescription-only medicines requiring clinical assessment. Eligibility is based on your BMI and individual health circumstances. You can check your current BMI using our free BMI calculator above to understand where you stand on NHS guidelines.
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.
Eligibility and How to Access Weight Loss Treatment in the UK
To be eligible for prescription weight loss medication in the UK, you typically need a BMI of 30 kg/m² or above, or a BMI of 27–29.9 kg/m² if you have weight-related health conditions such as type 2 diabetes, high blood pressure, or sleep apnoea. Adults of South Asian, Chinese, Black African, or Black Caribbean heritage may be eligible at lower BMI thresholds due to higher health risks at these levels.
You can access prescription weight loss treatment through the NHS specialist weight management services (tier 3) by asking your GP for a referral, though waiting times vary by region. Alternatively, private online clinics offer prescription weight loss treatment following an online clinical assessment. Have a conversation with your GP about which option is 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.
Does collagen actually help with weight loss?
Collagen may support muscle maintenance and satiety due to its high protein content, but there is no strong clinical evidence that collagen supplements directly cause weight loss. Collagen is not a licensed weight loss medication. If weight management is a priority, prescription options like Mounjaro, Wegovy, or Saxenda have clinical trial evidence behind them.
What's the difference between weight loss supplements and prescription medications?
Weight loss supplements like collagen are over-the-counter products with limited regulatory oversight and modest evidence. Prescription weight loss medications like Mounjaro and Wegovy are licensed by the MHRA, have undergone rigorous clinical trials, and require a GP or prescriber assessment. Only prescription options are evidence-based for significant, measurable weight loss.
How do I know if I'm eligible for NHS weight loss medication?
You may be eligible if your BMI is 30 or above, or 27–29.9 with weight-related health conditions. Use our free BMI calculator to check your current BMI. Your GP can then assess your individual circumstances and refer you to specialist weight management services if appropriate.
Can I get weight loss injections on the NHS?
Yes. The NHS offers prescription weight loss injections through tier 3 specialist weight management services, but access varies significantly by region and waiting lists can be long. Ask your GP for a referral to your local service. Private online prescribing is also available for eligible adults who prefer faster access.
How much weight could I lose with prescription medication?
Clinical trials show average weight loss of 15–21% of body weight with Mounjaro and around 15% with Wegovy over 68–72 weeks, alongside diet and exercise changes. However, individual results vary significantly. Use our free weight loss calculator to see projected outcomes, and discuss realistic expectations with your prescriber.
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.