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
Vitamins Good for Weight Loss — What Works in the UK
While certain vitamins support overall health, they're not effective for weight loss on their own. If you're looking for evidence-based support for weight management in the UK, prescription medications like Mounjaro and Wegovy are available for eligible adults. These are licensed GLP-1 medications that work alongside a reduced-calorie diet and physical activity. This guide explains UK prescription options, eligibility criteria, and how to discuss weight loss medication with your GP. Use our free BMI calculator above to check if you might qualify for support.
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 Loss Options
For eligible UK adults, three prescription medications are licensed for weight management: Mounjaro (tirzepatide), Wegovy (semaglutide), and Saxenda (liraglutide). These work differently to vitamins — they're GLP-1 receptor agonists that help regulate appetite and support feeling fuller after smaller meals.
- Mounjaro: 2.5–15 mg once weekly. Clinical trials showed average weight loss of 15–21% of body weight alongside diet and exercise.
- Wegovy: 0.25–2.4 mg once weekly. STEP trials showed average weight loss of approximately 15% of body weight.
- Saxenda: 0.6–3 mg once daily. Earlier clinical data supports modest weight loss benefits.
All three are prescription-only and require a clinical assessment before being prescribed. Individual results vary significantly. Access is available through NHS specialist weight management services or private online prescribing in the UK.
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.
Eligibility and How to Get Started
You may be eligible for prescription weight loss medication if you have a BMI of 30 or above, or BMI of 27–29.9 with weight-related health conditions like type 2 diabetes, high blood pressure, or heart disease. Adults of South Asian, Chinese, Black African, or Black Caribbean heritage may qualify at lower BMI thresholds.
Start by speaking to your GP about NHS weight loss support. They can refer you to a specialist tier 3 or 4 weight management service, though waiting lists vary by region. Alternatively, you can access prescription weight loss medications privately through a UK-licensed prescriber following an online clinical assessment. Track your progress with our free progress tracker once you begin treatment.
- 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 help with weight loss?
Vitamins support overall health and metabolism, but they don't cause weight loss on their own. A balanced diet with adequate vitamin intake matters, but weight loss requires a calorie deficit. Prescription medications like Mounjaro and Wegovy work through specific hormonal pathways and are far more effective for weight management.
What's the difference between Mounjaro and Wegovy?
Both are GLP-1 medications, but Mounjaro (tirzepatide) is a dual GIP and GLP-1 agonist, while Wegovy (semaglutide) is a GLP-1 agonist only. Clinical trials showed Mounjaro may help slightly more weight loss on average, but individual results vary. Both are prescription-only and require clinical assessment.
How do I know if I'm eligible for prescription weight loss medication?
You may qualify if your BMI is 30 or above, or 27–29.9 with weight-related health conditions. Ethnicity-adjusted thresholds are lower for certain groups. Your GP or a licensed prescriber can assess your eligibility. Use our free BMI calculator to check your starting point.
What's the difference between NHS and private weight loss medication access?
NHS access is through specialist weight management services — usually tier 3 or 4 — with referral from your GP. Private access is through online prescribers and GPhC-registered pharmacies without NHS referral. NHS availability varies by region; private access is often faster but has a cost.
Do I need to change my diet and exercise if I take Mounjaro or Wegovy?
Yes. These medications work best alongside a reduced-calorie diet and increased physical activity. Clinical trials included both dietary and lifestyle changes. Medication alone won't produce lasting results — it's a tool to support behaviour change, not a replacement for it.
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.