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
Is Collagen Good for Weight Loss?
Collagen supplements are popular in the UK health market, but evidence for weight loss is limited. While collagen may support skin and joint health, it doesn't meaningfully reduce body weight on its own. If you're looking for evidence-based weight management options in the UK, prescription medications like Mounjaro (tirzepatide) and Wegovy (semaglutide) have strong clinical trial data supporting weight loss. This guide explains why collagen alone won't help you lose weight, and what prescription options are actually available to eligible UK adults. Start by checking your BMI using our free BMI calculator above to understand your current health status.
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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 Prescription Weight Loss Medication
If you're interested in weight management in the UK, prescription weight loss medication offers much stronger evidence than collagen supplements. Two main options are currently licensed:
- Mounjaro (tirzepatide) — a dual GIP and GLP-1 receptor agonist. In clinical trials, it helped participants lose an average of 15–21% of their body weight over 72 weeks, alongside a reduced-calorie diet and increased physical activity.
- Wegovy (semaglutide) — a GLP-1 receptor agonist. Clinical trial data showed an average weight loss of approximately 15% of body weight at the maximum dose.
- Saxenda (liraglutide) — an older GLP-1 option, administered as a daily injection rather than once-weekly.
All three are prescription-only medicines requiring clinical assessment. Individual results vary significantly. Try our free GLP-1 weight loss calculator to explore potential outcomes at different doses if you're eligible.
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.
Who Is Eligible and How to Access These Medications in the UK
You may be eligible for prescription weight loss medication if you have a BMI of 30 or above, or 27–29.9 with a weight-related health condition (such as type 2 diabetes, high blood pressure, or sleep apnoea). Access in the UK works two ways: through the NHS via your GP (referred to specialist tier 3 services, though waiting lists vary significantly by region), or privately through an online prescriber following a clinical assessment.
Your first step is to speak with your GP about weight management options available in your area. They can assess your eligibility, discuss your health goals, and explain both NHS and private pathways. Using our weight converter and progress tracker, you can track your weight in the units you prefer whilst exploring your options with your healthcare provider.
- 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.
Why isn't collagen effective for weight loss?
Collagen is a protein, but it doesn't contain compounds that regulate appetite or metabolism the way prescription weight loss medications do. Collagen may support skin elasticity and joint health, but these benefits are separate from weight management. Clinical evidence for collagen-specific weight loss is minimal, whereas GLP-1 and GIP/GLP-1 medications have robust trial data.
What's the difference between Mounjaro and Wegovy for weight loss?
Mounjaro uses a dual GIP and GLP-1 mechanism, whilst Wegovy uses GLP-1 only. In clinical trials, Mounjaro showed slightly higher average weight loss (15–21%) compared to Wegovy (approximately 15%), but individual results vary. Both are once-weekly injections and require prescription. Your prescriber will assess which is more suitable for you.
Can I get prescription weight loss medication on the NHS?
Yes, but access is through specialist weight management services (tier 3), not routine GP prescription. You'll need referral from your GP, and availability varies significantly across UK regions. Some areas have short waiting lists; others have long delays. Private access via online prescribers is often faster, though costs apply.
How much weight will I lose with prescription medication?
This varies considerably between individuals. Clinical trials show average weight loss of 15–21% of body weight over several months, but some people lose more and some less. Results depend on your starting weight, adherence, diet, physical activity, and individual metabolism. Your prescriber can discuss realistic expectations for your situation.
Is prescription weight loss medication safer than supplements like collagen?
Prescription medications like Mounjaro and Wegovy have undergone rigorous clinical trials and are monitored by the MHRA. They do have side effects (mainly nausea and digestive changes), but their safety profile is well-documented. Collagen supplements are generally well-tolerated but lack evidence for weight loss. Always discuss any new medication or supplement with your GP before starting.
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.