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
Weight Loss Supplement Reviews — What Really Works in the UK
Weight loss supplements are widely marketed in the UK, but the evidence for most is limited. This guide reviews common supplements, explains what clinical research shows, and explores prescription alternatives that have stronger evidence backing. Whether you're looking for herbal options or prescription medications, understanding what actually works is essential for making an informed health decision.
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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.
Over-the-Counter Supplements vs Prescription Options
Most over-the-counter weight loss supplements sold in the UK have minimal clinical evidence. Common ingredients like caffeine, green tea extract, and conjugated linoleic acid (CLA) show modest effects in research — typically resulting in only 1–3 kg additional loss compared to diet alone. The challenge is that supplement quality varies, ingredients aren't always what labels claim, and the Food Standards Agency does not regulate supplements as strictly as medicines.
By contrast, prescription weight loss medications have undergone rigorous clinical trials. Wegovy (semaglutide) and Mounjaro (tirzepatide) are licensed by the MHRA specifically for weight management. In clinical trials, Wegovy helped participants lose an average of around 15% of their body weight, whilst Mounjaro achieved approximately 15–21% average loss — substantially more than supplements. Both are prescription-only medicines requiring a clinical assessment from a UK-licensed prescriber.
- Supplements: limited evidence, unregulated quality, modest results
- Prescription medications: clinical trial evidence, MHRA-approved, stronger outcomes
- NHS weight management: structured programmes combining diet, exercise, and medication where appropriate
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.
How to Evaluate Weight Loss Claims
When reviewing any weight loss product — supplement or otherwise — look for clinical trial data published in peer-reviewed journals, not just marketing claims. Check whether the research was funded by the product manufacturer (potential bias) and whether results were sustainable long-term.
The NHS recommends a sustainable approach combining a reduced-calorie diet, increased physical activity, and behaviour change support. For weight management in the UK, you can access tier 1 support (digital tools and community programmes) through your GP, or request referral to specialist tier 3 services where prescription weight loss medication may be considered. Try our free weight loss calculator to explore projected outcomes with evidence-based options, and use our BMI calculator to assess your starting point and healthy weight range.
- 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.
Are weight loss supplements regulated in the UK?
Supplements are regulated less strictly than medicines by the Food Standards Agency. They don't require the same clinical evidence as prescription medications. Always check the product label for a UK Medicines and Healthcare products Regulatory Agency (MHRA) registration if claiming therapeutic effects.
Do herbal weight loss supplements work?
Limited evidence supports most herbal supplements for significant weight loss. Ingredients like caffeine and green tea extract show modest effects (1–3 kg additional loss in trials), but results vary widely between individuals and studies are often small or industry-funded.
What's the difference between Wegovy and over-the-counter supplements?
Wegovy (semaglutide) is prescription-only and MHRA-approved with strong clinical trial evidence showing average clinically studied weight loss. Supplements are unregulated, lack substantial clinical backing, and typically produce minimal results. Wegovy requires clinical assessment; supplements do not.
Can I get prescription weight loss medication through the NHS?
Yes, through specialist tier 3 weight management services. Your GP can refer you, or you can access private prescribing through UK-licensed online prescribers following a clinical assessment. NHS availability varies by region and there may be waiting lists.
Should I use supplements alongside prescription weight loss medication?
Always discuss any supplements with your prescriber before combining them with prescription medication. Some supplements may interact with medicines like Wegovy or Mounjaro, and combining treatments without professional guidance could be unsafe.
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.