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
What Supplements Aid Weight Loss?
Many people search for supplements to support weight loss, but the evidence shows that most over-the-counter supplements have limited impact on their own. The most effective approaches to weight management in the UK combine lifestyle changes—reduced-calorie diet and increased physical activity—with evidence-based interventions. For significant weight loss, prescription weight loss medication and NHS weight management programmes offer stronger clinical support than supplements alone. This guide explores what the research actually shows about supplements, and what genuinely works for sustainable 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.
Which Supplements Have Research Behind Them?
Several supplements have been studied for weight loss, though most show modest effects at best. Caffeine may modestly increase metabolism and fat burning, particularly when combined with exercise. Green tea extract contains catechins that studies suggest may support fat oxidation, though results are variable. Glucomannan (a dietary fibre) may help people feel fuller, reducing overall calorie intake. Conjugated linoleic acid (CLA) has been researched for body composition but evidence is mixed. Protein powders can be useful as part of a reduced-calorie diet because protein increases satiety and helps preserve muscle during weight loss.
However, none of these supplements produce significant weight loss on their own. The NHS weight loss guidance emphasises that supplements work best alongside dietary changes and increased physical activity. Individual results vary considerably, and quality varies across commercial supplement brands.
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 Supplements
If you're seeking more effective weight management options in the UK, prescription weight loss medications have substantially stronger clinical evidence than supplements. GLP-1 weight loss injections like Mounjaro (tirzepatide) and Wegovy (semaglutide) are prescription-only medicines that work through a different mechanism than supplements—they activate natural hormone pathways that regulate appetite and food intake.
In clinical trials, Mounjaro helped participants lose an average of 15–21% of body weight, whilst Wegovy showed average losses around 14–15%—far greater than most supplements achieve. Both are available through NHS specialist weight management services or private online prescribing following a clinical assessment. Use our free GLP-1 weight loss calculator to estimate potential results, and our BMI calculator to check your starting point for NHS eligibility. For sustainable weight management, prescription options combined with lifestyle changes offer evidence-based support that supplements alone typically cannot provide.
- 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?
Most over-the-counter supplements have limited evidence and produce modest results at best. Those with some research—like caffeine, green tea extract, and glucomannan—may have small effects but are not substitutes for lifestyle changes or prescription medication. Individual results vary, and the NHS emphasises that sustainable weight loss requires reduced-calorie diet and increased physical activity.
What's the difference between supplements and prescription weight loss medication?
Supplements are unregulated and generally have weak evidence. Prescription medications like Mounjaro and Wegovy are rigorously tested medicines that activate hormone pathways controlling appetite. Clinical trials show prescription weight loss medications produce 15–21% average weight loss compared to 1–3% with most supplements.
Can I use supplements instead of seeing my GP about weight management?
No. If you're concerned about your weight, speak to your GP first. They can assess your individual health, discuss lifestyle changes, refer you to NHS weight management services, or discuss prescription options if appropriate. Supplements should never replace medical advice.
Are weight loss supplements safe?
Supplements are less regulated than medications. Quality, purity, and safety vary between brands. Some can interact with medications or medical conditions. Always check with your GP or pharmacist before taking supplements, especially if you're on other medications or have existing health conditions.
Is there a quick weight loss supplement that works?
No supplement produces gradual weight management safely. The NHS recommends losing 0.5–1 kg per week for sustainable results. If you want faster, evidence-backed results, prescription weight loss medication is more effective—but always requires clinical assessment and is combined with lifestyle changes.
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.