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
Do Supplements Really Help with Weight Loss?
Weight loss supplements are widely advertised in the UK, but the evidence supporting most of them is limited. While some natural ingredients may offer modest support, sustainable weight management typically requires dietary changes and increased physical activity. This guide explains what the research shows about popular supplements, how they compare to prescription weight loss medication, and how to approach weight management safely and effectively.
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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.
Popular Weight Loss Supplements and What Research Shows
Common weight loss supplements sold in UK health shops and online include caffeine, green tea extract, conjugated linoleic acid (CLA), glucomannan, and garcinia cambogia. The evidence for most is weak or inconclusive. Green tea extract may support modest fat oxidation when combined with exercise. Glucomannan, a soluble fibre, may help with satiety if taken with adequate water. However, most supplements show only small effects in clinical studies — typically less than 1–2 kg weight loss over several months, and often not significantly better than placebo.
- Caffeine: May increase energy and slightly boost metabolism, but effects are temporary and individual tolerance varies
- Green tea extract: Some evidence for modest metabolic support alongside exercise
- Fibre supplements: May aid feeling fuller, but whole foods like vegetables are more effective
- Herbal blends: Usually lack robust clinical trial data in the UK
The NHS does not recommend relying on supplements as a primary weight management strategy. Regulatory standards in the UK mean supplements are not subject to the same rigorous testing as prescription medications, so quality and ingredient accuracy can vary significantly between brands.
Clinically BackedWeight Loss
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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.
Prescription Weight Management — Evidence-Based Alternative
If you're struggling with weight management through diet and exercise alone, prescription weight loss medications offer a more evidence-based approach. GLP-1 weight loss injections like Wegovy (semaglutide) have been extensively studied in clinical trials and may support significant weight loss when combined with lifestyle changes. Mounjaro (tirzepatide), a dual GIP/GLP-1 agonist, has shown similar or greater results in clinical trials. Both are prescription-only and require a clinical assessment to determine if they're suitable for you.
Use our free BMI calculator to assess your current weight category, and our GLP-1 weight loss calculator can help you estimate potential results with prescription medication. NHS weight management services are available through your GP, though access varies by region. Private prescribing is also available following an online clinical assessment with a UK-licensed prescriber.
Sustainable weight loss typically requires a calorie deficit of around 500 kcal per day, resulting in approximately 0.5–1 kg weight loss per week — the NHS-recommended safe rate. While supplements may provide psychological reassurance, they cannot create the calorie deficit needed for meaningful weight loss. A balanced, reduced-calorie diet with whole foods (vegetables, lean proteins, whole grains) combined with regular physical activity remains the foundation of successful weight management. Track your progress using our free progress tracker to stay motivated and accountable over time.
- 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?
Weight loss supplements are regulated as food products, not medicines, so they undergo less rigorous testing than prescription medications. The MHRA monitors supplements for safety, but manufacturers do not need to prove effectiveness. Always check ingredient lists and buy from reputable UK retailers.
Can supplements replace diet and exercise?
No. Supplements cannot create the calorie deficit needed for weight loss. Diet and exercise are the foundation. Supplements may offer modest additional support, but they're not a substitute for lifestyle changes.
How do GLP-1 injections compare to supplements?
GLP-1 medications like Wegovy have been proven in large clinical trials to support significant weight loss — typically 14–21% of body weight. Supplements typically show minimal effects (1–2 kg). However, GLP-1 medications are prescription-only and require clinical assessment.
Is it safe to mix supplements with weight loss medication?
Some supplements may interact with prescription medications. Always inform your GP or prescriber of all supplements you're taking before starting any weight loss treatment. Your prescriber can advise on safety.
What's the fastest way to lose weight safely in the UK?
The NHS recommends losing 0.5–1 kg per week as the safe, sustainable rate. A 500 kcal daily deficit through diet and exercise achieves this. Prescription weight loss medication, used alongside lifestyle changes, may accelerate results under medical supervision.
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.