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 Over The Counter Weight Loss Supplement in the UK
When searching for over-the-counter weight loss supplements in the UK, it's important to understand what's actually available and what the evidence shows. The truth is that most over-the-counter supplements have limited clinical support for significant weight loss. If you're looking for evidence-based options, prescription weight loss medications like Mounjaro and Wegovy have strong clinical trial data behind them. This guide covers what OTC supplements exist, their effectiveness, and why many UK adults turn to prescription alternatives for meaningful results alongside healthy eating and increased physical activity.
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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 Over-The-Counter Weight Loss Supplements Are Available?
The UK supplements market includes several over-the-counter products marketed for weight management, though clinical evidence for most is limited. Common options include caffeine-based supplements, which may provide modest metabolic support, fibre-based products like glucomannan that can increase satiety, and herbal blends containing ingredients like green tea extract or conjugated linoleic acid (CLA). Most of these show only small, short-term weight loss effects in research. The Medicines and Healthcare products Regulatory Agency (MHRA) regulates supplements in the UK, but the bar for approval is lower than for prescription medications. Important consideration: over-the-counter supplements do not require clinical assessment before use, which means there's no personalised evaluation of whether they're suitable for your individual health profile. Many UK adults find that prescription weight loss medication, which requires a clinical assessment and GP or prescriber involvement, offers more substantial and measurable support for their weight management journey.
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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 OTC Supplements
Prescription options like Wegovy (semaglutide) and Mounjaro (tirzepatide) have substantially stronger clinical evidence than over-the-counter supplements. In the STEP-1 trial, semaglutide resulted in an average weight loss of approximately 14.9% of body weight, whilst most OTC supplements show results of 2–4% at best. Prescription weight loss medications work on the body's natural hormone systems — GLP-1 agonists like Wegovy mimic the GLP-1 hormone to reduce appetite and increase satiety, whilst Mounjaro uses a dual GIP and GLP-1 mechanism for potentially greater effect. Both require a prescription and clinical assessment to ensure they're safe and appropriate for you. Alongside dietary changes and increased physical activity, these offer measurable support. If you're considering weight loss support, use our free BMI calculator to establish your current health context, and speak with your GP about whether prescription weight loss medication might be suitable for you.
- 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 over-the-counter weight loss supplements safe?
Most OTC supplements sold in the UK are safe for healthy adults when used as directed, as they're regulated by the MHRA. However, safety depends on individual health conditions, existing medications, and ingredients. Some can interact with medications or affect certain health conditions. Always read labels carefully and discuss with your GP if you have any medical conditions or take other medicines.
Do over-the-counter weight loss supplements actually work?
Clinical evidence for most OTC supplements is limited. Whilst some ingredients like caffeine may provide modest metabolic benefits, average weight loss is typically 2–4% of body weight. Results are not assured and vary significantly between individuals. Weight loss is most effective when supplements are combined with reduced-calorie diet and increased physical activity.
What's the difference between OTC supplements and prescription weight loss medication?
Prescription medications like Wegovy and Mounjaro have strong clinical trial data showing average weight loss of 15–21% of body weight, compared to 2–4% for most supplements. Prescription medications require clinical assessment and a prescriber's evaluation, whilst supplements do not. Prescription options work on natural hormone pathways and may be more effective for meaningful, sustained weight loss.
Can I get prescription weight loss medication on the NHS?
Prescription weight loss medications like Mounjaro and Wegovy are available through NHS specialist weight management services (tier 3), though availability varies significantly by region and there may be waiting lists. You can also access these medications privately through online prescribing services following a clinical assessment. Your GP can advise on NHS access in your area.
What should I do if I'm struggling to lose weight?
Start by speaking with your GP, who can assess your individual situation and rule out underlying health conditions. Use our free BMI calculator to understand your current health context. If diet and lifestyle changes alone aren't working, ask about referral to specialist weight management services or discuss whether prescription weight loss medication might be appropriate. Track your progress using our free weight loss progress tracker.
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.