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
Best Supplements for Weight Loss in the UK
Supplements marketed for weight loss are popular in the UK, but most lack strong scientific evidence. While some may provide modest support for weight management when combined with a reduced-calorie diet and physical activity, they are not a substitute for lifestyle changes. This guide covers evidence-based supplements, their limitations, and when prescription weight loss medication might be appropriate. Always consult your GP before starting any new supplement, especially if you take other medications or have existing health conditions.
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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.
What the Evidence Shows About Weight Loss Supplements
Most common weight loss supplements show limited scientific evidence for effectiveness in UK clinical trials. Caffeine and green tea extract may provide modest support (approximately 1–3 kg additional loss over several months), but effects are small and vary between individuals. Glucomannan (soluble fibre) can help with satiety if adequate water is consumed, while conjugated linoleic acid (CLA) shows mixed results. Garcinia cambogia, forskolin, and many herbal blends lack robust evidence. The NHS advises that diet and physical activity remain the foundation of weight management. Supplements should never replace these core strategies. Quality varies significantly between brands — look for third-party tested products. Use our free BMI calculator to establish your current weight status before selecting any supplement approach.
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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.
When Supplements Aren't Enough: Prescription Weight Loss Options
If you have a BMI of 30 or above (or 27 or above with weight-related health conditions), prescription weight loss medication may be more effective than supplements. GLP-1 weight loss injections like Mounjaro and Wegovy are licensed in the UK and have stronger clinical evidence than most supplements — clinical trials showed average weight loss of 15–21% of body weight. These are prescription-only and require a clinical assessment. Your GP can refer you to NHS specialist weight management services, or you can access private prescribing through a licensed UK prescriber. Try our GLP-1 weight loss calculator to explore potential outcomes with prescription medication, and use our weight converter to track progress in your preferred units.
- 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 show modest evidence—caffeine and green tea may support 1–3 kg additional loss when combined with diet and exercise. However, most lack strong clinical evidence. They work best alongside lifestyle changes, not as replacements. Always check with your GP before starting any supplement.
What's the best supplement for weight loss in the UK?
No single "best" supplement exists. Glucomannan (fibre), caffeine, and green tea extract have the most evidence, but effects are small. Your GP or a registered nutritionist can recommend options based on your individual health. Consider lifestyle changes as your primary strategy.
Are weight loss supplements safe?
Quality and safety vary. Some supplements interact with medications or have side effects. Always inform your GP of any supplements you're considering, especially if you take other medicines. Look for third-party tested products and avoid unregulated herbal blends.
Should I use supplements or ask my GP about prescription weight loss medication?
If your BMI is 30 or above (or 27+ with health conditions), prescription options like GLP-1 injections have stronger evidence than supplements. Ask your GP about referral to specialist weight management services, which can assess your suitability for prescription treatment.
How do I track weight loss from supplements?
Use our free progress tracker on MyWeightCheck to log weekly weight changes. Record your starting weight, BMI, and measurements. This helps you assess whether supplements are genuinely supporting your goals or whether a different approach (including prescription options) might be more effective.
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.