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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Safe Dietary Supplements For Weight Loss: What Works?
If you're looking to lose weight in the UK, you may have heard about dietary supplements claiming to support weight management. While some supplements have modest evidence behind them, the safest and most effective approach combines lifestyle changes with evidence-based options — and understanding what actually works is essential. This guide covers the science, NHS guidance, and what you need to know before trying any supplement for weight loss.
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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 Dietary Supplements for Weight Loss
Several dietary supplements have some scientific support for weight management, though most show modest effects:
- Glucomannan — a soluble fibre that absorbs water and may help you feel fuller. Evidence suggests modest weight loss when combined with diet and exercise.
- Green tea extract — contains catechins that may slightly increase fat burning. Effects are small and most noticeable with regular exercise.
- Conjugated linoleic acid (CLA) — a fatty acid that may support fat loss, though clinical trial results are mixed.
- Caffeine — well-established to modestly increase metabolism and energy. Most effective when combined with exercise.
- Whole grain and soluble fibre supplements — support satiety and digestive health, helping with portion control.
The NHS emphasises that no supplement replaces the fundamentals: a reduced-calorie diet, regular physical activity, and consistent lifestyle changes. Supplements work best as additions to, not replacements for, these proven strategies. Use our free BMI calculator above to check your current weight status and understand your baseline.
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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 Medication vs. Over-the-Counter Supplements
For NHS weight loss guidance, it's important to distinguish between dietary supplements (unregulated, over-the-counter) and prescription weight loss medications (regulated by the MHRA, require clinical assessment). If you're overweight or obese and interested in weight management support in the UK, your GP can discuss options with you.
Prescription GLP-1 medications such as Wegovy (semaglutide) or Mounjaro (tirzepatide) are licensed for weight management and work through a completely different mechanism than dietary supplements — they activate specific hormone pathways that regulate appetite. Clinical trials show significantly greater weight loss compared to supplements alone. However, these require a prescription and clinical assessment. Try our GLP-1 weight loss calculator to understand potential outcomes with medication-supported weight management.
Always consult your GP before starting any supplement or considering prescription options, especially if you take other medications or have existing health conditions.
- 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 dietary supplements for weight loss safe?
Most commonly used weight loss supplements have a reasonable safety profile when taken as directed, but quality and safety standards vary widely. The Medicines and Healthcare products Regulatory Agency (MHRA) does not regulate dietary supplements as strictly as prescription medications. Always check the source, read the label, and speak to your GP before starting any supplement — especially if you take other medications or have health conditions.
What's the difference between a dietary supplement and a weight loss medication?
Dietary supplements are unregulated products with modest evidence of effect. Prescription weight loss medications (like Wegovy or Mounjaro) are MHRA-licensed, require clinical assessment, and have strong clinical trial evidence. Prescription options are typically reserved for people with a BMI of 30 or above, or 27–29.9 with weight-related health conditions. Your GP can advise which approach suits you.
Can I use dietary supplements instead of lifestyle changes?
No. The NHS emphasises that sustainable weight management requires a reduced-calorie diet and increased physical activity — the foundation. Supplements can offer modest additional support, but no supplement replaces these fundamentals. A calorie deficit of around 500 kcal daily typically results in approximately 0.5 kg weight loss per week.
Should I try supplements before asking my GP about weight loss options?
You don't need to try supplements first. If you're concerned about your weight or BMI, it's always worth speaking to your GP. They can assess your individual situation, discuss all evidence-based options (including NHS weight management programmes, prescription medications, and healthy lifestyle approaches), and rule out underlying health issues affecting your weight.
How do I know if a weight loss supplement is evidence-based?
Look for supplements with clinical trial data published in peer-reviewed journals, not just marketing claims. The NHS and NICE provide evidence-based guidance. Be sceptical of supplements promising dramatic results or gradual weight management — sustainable, evidence-based weight loss is 0.5–1 kg per week. Your GP or a registered dietitian can recommend supplements with genuine support.
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.