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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OTC Weight Loss Supplements — What You Need to Know
Over-the-counter weight loss supplements are widely available in UK pharmacies and online, but evidence for most is limited. This guide covers what supplements are available, what the research actually shows, NHS weight loss guidance, and how prescription weight loss medication compares. If you're considering weight management, understanding your options—from supplements to evidence-based prescription treatments—is important for making an informed choice.
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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 OTC Weight Loss Supplements Are Available in the UK?
The UK market offers a range of non-prescription weight loss supplements, including caffeine-based products, conjugated linoleic acid (CLA), green tea extract, garcinia cambogia, konjac fibre, and glucomannan. These are sold as dietary supplements, not medicines, and are not subject to the same regulatory scrutiny as prescription medications.
- Caffeine supplements — may provide modest appetite suppression and slight metabolic boost; evidence is limited and effects are typically small
- Fibre supplements — soluble fibres like glucomannan may help with satiety and digestive health when combined with adequate water intake
- Herbal extracts — green tea and other plant-based products claim weight loss benefits but clinical evidence is weak for most
- CLA and other fatty acids — some studies suggest modest fat loss effects, though results are inconsistent
The NHS notes that most OTC supplements have limited scientific evidence for weight loss effectiveness. Unlike prescription weight loss medication or nhs weight loss programmes, supplements are not approved by medicines regulators and their quality and potency can vary significantly.
Clinically BackedWeight Loss
No appointments. No waiting rooms. Just care — from a UK-regulated online pharmacy.
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 weight loss injections like Mounjaro (tirzepatide) and Wegovy (semaglutide) have robust clinical trial data showing average weight loss of 15–21% body weight in SURMOUNT trials. These glp-1 weight loss medications work through well-understood biological mechanisms and are approved by the MHRA for weight management in eligible adults.
OTC supplements, by contrast, typically show much smaller effects (if any) in clinical studies. Prescription weight loss medication nhs guidelines recommend these treatments for adults with a BMI of 30 or above, or 27 or above with weight-related health conditions. If you qualify for prescription weight loss uk treatments, evidence suggests these are significantly more effective than over-the-counter options. Use our free BMI calculator to check if you may be eligible, and consult your GP about prescription alternatives.
- 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?
Many OTC supplements are generally safe at recommended doses, but safety varies. Some contain stimulants that may cause side effects like jitteriness or sleep disruption. Always check ingredients, avoid if pregnant or taking medications, and discuss with your GP before starting any supplement, especially if you have existing health conditions.
Do OTC weight loss supplements actually work?
Most OTC weight loss supplements show minimal evidence of effectiveness. Any weight loss is typically modest (0.5–2 kg over several weeks) and often not significantly better than diet and exercise alone. Prescription medications like GLP-1 injections show much stronger clinical evidence for weight loss.
What does the NHS say about weight loss supplements?
The NHS recommends focusing on evidence-based approaches: a balanced diet, regular physical activity, and behavioural support. For significant weight loss, NHS specialists may prescribe approved medications like tirzepatide or semaglutide rather than recommend unproven supplements.
How do GLP-1 weight loss injections compare to OTC supplements?
Prescription GLP-1 medications (Mounjaro, Wegovy) have strong clinical trial data showing 15–21% average body weight loss. OTC supplements typically show minimal effects. Prescription weight loss medication requires a clinical assessment and is available through NHS tier 3 services or private prescribing.
Should I try supplements before prescription weight loss medication?
If you have a BMI qualifying you for prescription weight loss treatment, evidence suggests prescription medications are more effective. Talk to your GP or a licensed prescriber about your options. Use our free GLP-1 weight loss calculator to explore potential outcomes with evidence-based medication.
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.