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 Dietary Supplements For Weight Loss In The UK
While dietary supplements are widely marketed for weight loss, the evidence for most is limited. In the UK, if you're looking to manage your weight effectively, prescription weight management medications have stronger clinical evidence and are available through the NHS or private prescribing. This guide explains the supplement landscape, compares evidence-based approaches, and introduces prescription options that may be suitable if you meet eligibility criteria. We'll help you understand what works and how to find personalised support for your weight management journey.
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.
UK-Licensed Prescription Weight Management Options
If you're struggling with weight management, prescription medications offer evidence-based alternatives to dietary supplements. In the UK, three medications are licensed specifically for weight loss: Mounjaro (tirzepatide), Wegovy (semaglutide), and Saxenda (liraglutide). These are not dietary supplements — they are prescription-only medicines that work by mimicking natural hormones that regulate appetite and blood sugar.
Eligibility criteria: You may be eligible for prescription weight loss medication if you have a BMI of 30 or above, or a BMI of 27–29.9 with weight-related health conditions such as type 2 diabetes, high blood pressure, or sleep apnoea. Clinical trials show that these medications, used alongside lifestyle changes, help people lose an average of 15–21% of their body weight — significantly more than most dietary supplements achieve. Use our free GLP-1 weight loss calculator to estimate potential results at different doses, and our BMI calculator to check your current BMI category.
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.
NHS vs Private Access — How To Get Started
In the UK, prescription weight loss medication is available through two routes. NHS access: Referral to a tier 3 specialist weight management service through your GP — however, waiting lists vary significantly by region and can be lengthy. Private access: Online consultation with a UK-licensed prescriber, prescription issued if clinically appropriate, dispensed by a registered pharmacy. Both routes require a clinical assessment to confirm you're suitable for treatment. If you're interested in exploring prescription options for weight management UK, start by discussing with your GP or consulting an online prescriber. They will assess your individual health, medical history, and eligibility. This personalised approach ensures you receive the right support.
- 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 dietary supplements effective for weight loss?
Most dietary supplements have limited clinical evidence for weight loss. While some ingredients like caffeine or fibre may provide modest support, the effects are small compared to prescription medications or lifestyle changes. Always check ingredients for safety and discuss with your GP before taking any supplements, especially if you're on other medications.
What's the difference between a dietary supplement and a prescription weight loss medication?
Dietary supplements are not strictly regulated and claims are not always evidence-based. Prescription weight loss medications, like Mounjaro and Wegovy, are licensed by the MHRA, have undergone clinical trials, and their safety and efficacy are proven. They require a prescription and clinical assessment before use.
How much weight can you lose with prescription weight loss medication?
Clinical trials show that Mounjaro and Wegovy help people lose an average of 15–21% of their body weight when used alongside a reduced-calorie diet and increased physical activity. Individual results vary significantly — some people lose more, others less. Our weight loss calculator can give you a personalised estimate.
How do I know if I'm eligible for prescription weight loss treatment on the NHS?
Eligibility generally requires a BMI of 30 or above, or 27–29.9 with weight-related health conditions. Speak with your GP, who can refer you to a specialist tier 3 weight management service for assessment. Alternatively, private online prescribers can assess your eligibility following an online consultation.
Is prescription weight loss medication better than trying dietary supplements first?
If you meet eligibility criteria, prescription weight loss medication has stronger clinical evidence. However, lifestyle changes — reduced-calorie diet, physical activity, and behaviour support — remain essential for sustainable weight management UK, whether or not you use medication. Your GP can advise on the best approach for your situation.
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.