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 Is The Best Vitamin For Weight Loss In The UK?
When it comes to weight loss, vitamins and supplements have limited scientific evidence for effectiveness. However, prescription weight management medication is available in the UK for eligible adults. If you're interested in losing weight, understanding your BMI, eligibility criteria, and the UK options available—from NHS specialist services to private prescribing—is far more valuable than relying on supplements alone. This guide covers the prescription alternatives that are clinically proven to support weight loss alongside lifestyle changes.
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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 Medication
For eligible UK adults, three prescription medications are licensed for weight management and offer evidence-based support for weight loss. Mounjaro (tirzepatide) is a once-weekly injection that works as a dual GIP and GLP-1 receptor agonist, helping regulate appetite and food intake. Clinical trials showed participants lost an average of 15–21% of their body weight. Wegovy (semaglutide) is a once-weekly GLP-1 injection, with trial data showing average weight loss of around 15% body weight. Saxenda (liraglutide) is a daily GLP-1 injection offering similar weight loss support.
To be eligible for prescription weight loss medication in the UK, you typically need a BMI of 30 or above, or 27–29.9 with weight-related health conditions such as type 2 diabetes, high blood pressure, or cardiovascular disease. Lower thresholds apply for adults of South Asian, Chinese, Black African, or Black Caribbean heritage due to higher health risks at lower BMI levels. Use our free BMI calculator to check your BMI instantly—this is the first step in understanding your eligibility.
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 Specialist Services Versus Private Access
In the UK, prescription weight loss medication is available through two main routes: NHS specialist weight management services and private online prescribing. NHS access typically requires referral from your GP to a tier 3 specialist service, though waiting times and availability vary significantly by region. Private prescribing offers faster access—you can complete an online consultation with a UK-licensed prescriber without an NHS referral, though you'll pay for the medication privately.
Your GP is the best starting point. They can assess whether you're eligible, discuss your weight management options, and either refer you to NHS specialist services or advise on private routes. Track your weight loss progress using our free progress tracker alongside any treatment you pursue. Remember, prescription medication works best when combined with reduced-calorie diet and increased physical activity.
- 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.
Is there a vitamin that actually helps with weight loss?
Most vitamins and supplements lack strong clinical evidence for weight loss. While B vitamins support metabolism and vitamin D is important for overall health, they won't produce meaningful weight loss on their own. Prescription weight loss medications like Mounjaro and Wegovy have robust clinical trial evidence supporting their effectiveness for eligible adults.
What's the difference between weight loss vitamins and prescription medication?
Supplements are largely unregulated and evidence for weight loss is weak. Prescription medications like GLP-1 injections are licensed, MHRA and MHRA-approved, and backed by large clinical trials. They work on specific appetite and metabolic pathways and require clinical assessment before prescribing.
How do I know if I'm eligible for prescription weight loss medication in the UK?
You're potentially eligible if you have a BMI of 30 or above, or 25–29.9 with weight-related health conditions. Lower BMI thresholds apply if you're of South Asian, Chinese, Black African, or Black Caribbean heritage. Book an appointment with your GP to discuss whether prescription treatment is right for you.
Can I access weight loss injections through the NHS?
Yes. Mounjaro and Wegovy are available through NHS specialist tier 3 weight management services. You'll need a GP referral, but availability varies by region and waiting times can be lengthy. Private prescribing offers faster access without NHS referral, though you'll pay privately.
What's the best approach if I want to explore weight loss options?
Start by calculating your BMI using our free BMI calculator to understand your current status. Then book a GP appointment to discuss your weight management goals and eligibility. Your GP can either refer you to NHS specialist services or advise on private prescribing options. Combine any medication with dietary changes and increased physical activity for best results.
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.