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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Best Dietary Supplements For Weight Loss
Dietary supplements are widely marketed for weight loss, but evidence for most is limited. This guide examines which supplements have scientific backing, how they compare to prescription weight management options, and what the NHS recommends. If you're exploring weight management options in the UK, understanding both supplements and prescription treatments can help you make an informed choice alongside diet and exercise.
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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.
Evidence-Based Weight Loss Supplements
Several supplements have research supporting modest weight loss effects when combined with a reduced-calorie diet and physical activity:
- Caffeine: May increase fat burning and energy expenditure. Typical dose 200–400mg daily. Effects are modest (1–2kg over several months).
- Green tea extract (EGCG): Contains catechins that may support fat oxidation. Evidence is mixed, with average weight loss around 1–3kg over 12 weeks.
- Glucomannan (soluble fibre): Absorbs water in the stomach, promoting fullness. May help with appetite control. Requires adequate water intake.
- Conjugated linoleic acid (CLA): Found in dairy and beef. Evidence suggests minimal weight loss benefit (approximately 0.5–1kg over several months).
Most supplements produce small, variable results. None are as effective as prescription weight loss medication or sustained lifestyle changes. Always check with your GP before starting any supplement, especially if you take other medications.
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 Loss vs Dietary Supplements
Prescription weight management medications have significantly stronger clinical evidence than supplements. GLP-1 medications like Wegovy (semaglutide) have demonstrated average weight loss of approximately 15% of body weight in clinical trials—far greater than dietary supplements. Prescription options are available through NHS weight management services or private prescribing following clinical assessment. Unlike supplements, prescription medications are regulated, quality-assured, and prescribed based on your individual health profile. Use our GLP-1 weight loss calculator above to estimate potential outcomes with prescription options, or check your BMI using our free BMI calculator to understand whether you may be eligible for prescription weight management.
The NHS recommends a comprehensive approach: sustainable weight management in the UK typically involves dietary changes (approximately 500 kcal daily deficit), increased physical activity, and behavioural support. Supplements can be part of this approach but should not be relied upon as primary treatment. If you're overweight or obese (BMI ≥25), your GP can discuss personalised options including NHS weight loss programmes, prescription medication eligibility, or structured dietary approaches. There is no single "best" supplement—consistency with lifestyle changes matters far more than any individual product.
- 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.
Do weight loss supplements actually work?
Some supplements like caffeine and green tea extract have modest scientific support, but effects are typically small (1–3kg over several months). Most weight loss supplements produce variable and inconsistent results. Prescription medications like GLP-1 treatments show significantly stronger evidence, with average weight loss around 15% of body weight. Lifestyle changes—diet and exercise—remain the foundation of sustainable weight management.
Which supplements are safest for weight loss?
Generally safe options with some evidence include caffeine (200–400mg daily), green tea extract, and glucomannan fibre. However, safety varies by individual health, medications, and underlying conditions. Always consult your GP before starting any supplement, especially if you have diabetes, heart conditions, or take medications. Some supplements can interact with medicines or aggravate existing health problems.
Are prescription weight loss medications better than supplements?
Yes. Prescription options like Wegovy (semaglutide) are NHS-licensed for weight management and have strong clinical trial evidence supporting significant weight loss. They require a prescription and clinical assessment but offer much greater effectiveness than dietary supplements. GLP-1 medications may help you lose approximately 15% of body weight alongside reduced-calorie diet and exercise—far superior to supplement results.
Can I get weight loss medication on the NHS?
Yes. The NHS funds prescription weight loss medications through specialist tier 3 weight management services. Access typically requires referral from your GP and assessment by a specialist team. Availability varies by region and waiting lists can be lengthy. Private prescribing is also available in the UK through online consultations with licensed prescribers following clinical assessment.
What does the NHS recommend for weight management?
The NHS recommends a sustainable approach: calorie deficit (approximately 0.5–1kg weekly loss), increased physical activity, and behavioural support. Supplements can be considered but are not primary treatment. Your GP can advise whether you're eligible for NHS weight management services, prescription medication, or community programmes. Use our free BMI calculator to check your starting point and discuss personalised options with your healthcare team.
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.