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
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Best Vitamins for Weight Loss — What Actually Works in the UK
Whilst certain vitamins and supplements are marketed for weight loss, the evidence is mixed — and vitamins alone won't deliver significant results. If you're looking for serious weight management UK support, prescription medications like Mounjaro and Wegovy have shown meaningful results in clinical trials. This guide explains what vitamins might help, why they're limited, and what prescription weight loss options are actually available to eligible UK adults.
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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.
Prescription Weight Loss Medication Available in the UK
If you have a BMI of 30 or above, or a BMI of 27–29.9 with weight-related health conditions like type 2 diabetes or high blood pressure, you may be eligible for prescription weight loss medication. The UK-licensed options are:
- Mounjaro (tirzepatide) — a dual GIP and GLP-1 receptor agonist. Clinical trials showed participants lost an average of 15–21% of their body weight. Once-weekly injection, doses from 2.5 mg to 15 mg.
- Wegovy (semaglutide) — a GLP-1 receptor agonist. Average weight loss around 15% of body weight in trials. Once-weekly injection, maximum dose 2.4 mg.
- Saxenda (liraglutide) — also a GLP-1 agonist. Daily injection, maximum dose 3 mg.
All three are prescription-only and require a clinical assessment. Weight loss with these medications is most effective when combined with a reduced-calorie diet and increased physical activity. Try our GLP-1 weight loss calculator to see estimated results at different doses.
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, you can access prescription weight loss medication through two routes. NHS access requires a referral from your GP to a specialist tier 3 weight management service — availability varies significantly by region and waiting lists can be lengthy. Private access is available through UK-licensed prescribers via online consultation, without needing an NHS referral.
Start by speaking to your GP about your weight management goals. They can assess your BMI and eligibility, discuss whether prescription medication is appropriate for you, and explain NHS options in your area. Use our free BMI calculator above to check your personal BMI before your appointment — this helps you understand where you fall on the NHS eligibility thresholds.
- 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.
Can vitamins and supplements help with weight loss?
Some vitamins may support metabolism and energy (like B vitamins), but clinical evidence for weight loss is weak. Supplements are not regulated as strictly as medications. Vitamin deficiencies should be corrected, but vitamins alone won't deliver significant weight loss. For meaningful results, prescription medication combined with diet and exercise is more effective.
What's the difference between Mounjaro and Wegovy for weight loss?
Mounjaro (tirzepatide) activates two hormone pathways (GIP and GLP-1), while Wegovy (semaglutide) activates only GLP-1. Clinical trial data shows Mounjaro users lost slightly more weight on average (15–21% vs approximately 15%). Both are once-weekly injections, but Mounjaro has higher maximum doses. Choice depends on individual suitability assessed by a prescriber.
Do I need to change my diet if I take weight loss medication?
Yes. GLP-1 and GIP/GLP-1 medications work best alongside a reduced-calorie diet and regular physical activity. Medications help reduce appetite and support feeling fuller, but they're not a replacement for lifestyle changes. Clinical trials combined medication with structured diet and exercise programmes for best results.
How do I know if I'm eligible for prescription weight loss treatment in the UK?
You're potentially eligible if you have a BMI of 30 or above, or a BMI of 27–29.9 with at least one weight-related health condition (type 2 diabetes, high blood pressure, high cholesterol, or sleep apnoea). Your GP can assess your eligibility and discuss whether medication is appropriate for you.
Will the NHS prescribe these medications, or do I need to go private?
Both options exist in the UK. NHS access is through specialist tier 3 weight management services — you need a GP referral and availability varies by region. Private access is faster, available without referral, but costs approximately £129–£320 per month depending on dose and provider. Your GP can explain what's available in your area.
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.