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
Which Supplement Is Best For Weight Loss?
There's no single "best" weight loss supplement — the right choice depends on your health, BMI, and what you're looking for. In the UK, the most effective evidence-backed options are prescription weight loss medications (not traditional supplements), alongside lifestyle changes like diet and exercise. If you have a BMI of 30 or above, or 27 or above with weight-related health conditions, you may be eligible for prescription options like Mounjaro or Wegovy. For others, proven approaches include calorie deficit, physical activity, and consulting your GP about personalised weight management UK strategies.
10,000+ calculations today · NHS-aligned thresholds · 100% free
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.
Prescription Weight Loss Medications vs Traditional Supplements
When people ask "which supplement is best", they're often confusing traditional supplements (like vitamins or herbal products) with prescription weight loss medications. The distinction matters:
Traditional supplements (green tea extract, conjugated linoleic acid, glucomannan) show modest evidence for weight loss but results are usually small — often just 1–3kg over several months. They're not regulated as strictly as medications and individual results vary widely.
Prescription weight loss medications like Wegovy (semaglutide) and Mounjaro (tirzepatide) are NHS-approved and show much stronger evidence. In clinical trials, Wegovy helped participants lose an average of approximately 15% of their body weight, while Mounjaro showed average losses of 15–21%. Both work by reducing appetite and helping you feel fuller after smaller meals. These require a prescription following clinical assessment and are used alongside diet and exercise. Prescription weight loss medication is part of nhs weight loss pathways for eligible adults.
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.
How to Choose: Evidence-Based Weight Loss Approach
The best approach depends on your eligibility and health needs. First, calculate your BMI using our free BMI calculator above to see if you're in a category where prescription medication might help. If your BMI is under 25, focus on lifestyle: calorie deficit, increased physical activity, and reducing processed foods show the strongest, most sustainable results.
For glp-1 weight loss medication eligibility (BMI 30+, or 27+ with conditions like diabetes or high blood pressure), speak to your GP about referral to specialist weight management services, or consult a licensed prescriber. Track your progress with our free progress tracker to monitor both weight and lifestyle changes. Remember: medication works best alongside reduced-calorie diet and physical activity, not instead of them.
- 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 effective?
Some show modest evidence — glucomannan fibre may help with appetite, green tea extract may support modest fat loss. However, results are typically small (1–3kg) and inconsistent. They're not regulated like medications, so quality varies. Prescription weight loss medications show much stronger clinical evidence and are a better choice if you're eligible.
What's the difference between Wegovy and over-the-counter supplements?
Wegovy is a prescription GLP-1 injection licensed specifically for weight management in the UK. Clinical trials showed average weight loss of approximately 15% of body weight. Over-the-counter supplements lack this level of clinical evidence and regulatory oversight. Wegovy requires a prescription and clinical assessment — it's not available without professional evaluation.
Can I get weight loss medication on the NHS?
Yes. If you have a BMI of 30 or above, or 27+ with weight-related health conditions, you may be eligible for prescription weight loss treatment through NHS specialist weight management services. Access varies by region. Your GP can refer you to tier 3 services. Private online prescribing is also available if NHS waiting lists are long in your area.
What's the safest way to lose weight — supplements or prescription medication?
Both should be combined with calorie deficit and exercise. Prescription medications like Mounjaro and Wegovy are formally tested and monitored by the MHRA. If eligible, they offer stronger, evidence-backed results than most supplements. Any medication or significant supplement use should be discussed with your GP first.
How quickly can I expect weight loss results?
With prescription weight loss medication, results typically appear within 4–8 weeks but vary by individual. With traditional supplements, results (if any) are slower. The NHS recommends losing 0.5–1kg per week as sustainable. Use our free progress tracker to monitor your journey and stay motivated over time.
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.