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
Nutritional Supplements for Weight Loss — UK Prescription Options
Nutritional supplements are popular for weight management, but many lack strong clinical evidence. If you're looking to lose weight in the UK, it's worth knowing that prescription weight loss medications — such as Mounjaro and Wegovy — are now available for eligible adults. These prescription options have clinical trial data backing their effectiveness. This guide explains the difference between supplements and prescription weight management, who qualifies for NHS or private weight loss medication, and how to get started. Use our free BMI calculator above to check your current weight status and explore whether prescription options might be right for you.
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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.
UK-Licensed Prescription Weight Loss Options
If you're considering nutritional supplements for weight loss, you should also know about prescription alternatives available in the UK. Three medications are currently licensed for weight management: Mounjaro (tirzepatide), Wegovy (semaglutide), and Saxenda (liraglutide). All are prescription-only and require a clinical assessment before use. Mounjaro and Wegovy are once-weekly injections, whilst Saxenda is a daily injection. Unlike many supplements, these medications have undergone rigorous clinical trials. In trials, Mounjaro helped participants lose an average of 15–21% of their body weight, and Wegovy around 15%, when used alongside a reduced-calorie diet and increased physical activity. Individual results vary significantly. You can use our free GLP-1 weight loss calculator to explore potential outcomes at different dose levels.
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 Access, Eligibility, and Next Steps
Prescription weight loss medication is available through both NHS specialist services and private online prescribing in the UK. NHS access is through tier 3 specialist weight management services — typically requiring a GP referral. Eligibility includes a BMI of 30 or above, or 27–29.9 with weight-related health conditions such as type 2 diabetes, high blood pressure, or sleep apnoea. For adults of South Asian, Chinese, Black African, or Black Caribbean heritage, lower BMI thresholds apply. Private prescribing is available without NHS referral through UK-licensed online prescribers. The first step is a conversation with your GP about your weight loss options. They can assess your health, discuss whether prescription medication is appropriate, and refer you to NHS specialist services if suitable. Track your progress with our free progress tracker as part of your weight management journey.
- 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 nutritional supplements as effective as prescription weight loss medication?
Most nutritional supplements lack robust clinical trial evidence. Prescription medications like Mounjaro and Wegovy have undergone rigorous clinical trials showing significant average weight loss. However, individual results vary. Your GP can discuss which option is most appropriate for your health situation.
Do I need to be referred to an NHS specialist to get prescription weight loss medication?
For NHS access, you typically need a GP referral to a tier 3 specialist weight management service. Private prescribing is available through UK-licensed online prescribers without NHS referral. Eligibility and wait times vary by region and provider.
What's the difference between Mounjaro and Wegovy for weight loss?
Both are prescription-only once-weekly injections. Mounjaro (tirzepatide) is a dual GIP and GLP-1 agonist; Wegovy (semaglutide) is a GLP-1 agonist only. In trials, Mounjaro showed slightly higher average weight loss, but results vary between individuals. A prescriber will advise which is most suitable for you.
Who is eligible for prescription weight loss medication in the UK?
Adults with a BMI of 30 or above, or 27–29.9 with weight-related health conditions (type 2 diabetes, hypertension, sleep apnoea), may be eligible. Lower BMI thresholds apply for South Asian, Chinese, and Black African/Caribbean adults. A clinical assessment determines individual eligibility.
How do I find out if I'm eligible for weight loss medication?
Start with a conversation with your GP about weight management options. They can assess your health, BMI, and any existing health conditions to advise whether prescription medication is suitable. Use our free BMI calculator to check your current BMI before your appointment to help guide the discussion.
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.