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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Thyroid Vitamins, Weight Loss, and UK Prescription Options
If you're interested in thyroid vitamins and weight loss, it's important to understand that thyroid health and weight management are connected — but prescription weight loss medication may also be an option if you're eligible. The UK has several licensed weight management options available through the NHS and privately, including GLP-1 injections like Mounjaro and Wegovy. This guide explains what's available, who qualifies, and how to find out whether prescription weight loss medication might be right for you. Always speak to your GP before making any changes to your health routine.
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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 Weight Loss Medication Options
For adults struggling with weight management in the UK, several prescription medications are now available. Mounjaro (tirzepatide) is a once-weekly injection that acts as a dual GIP and GLP-1 receptor agonist. Clinical trials showed average weight loss of approximately 15–21% of body weight over 72 weeks, though individual results vary. Wegovy (semaglutide) is another once-weekly GLP-1 injection with average weight loss around 15% in clinical trials. Saxenda (liraglutide) is a daily GLP-1 injection option.
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 cardiovascular disease. For adults of South Asian, Chinese, Black African, or Black Caribbean heritage, eligibility may start at lower BMI thresholds. Use our free BMI calculator above to check your BMI instantly and see where you fall on the NHS scale.
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: Referral to a tier 3 specialist weight management service through your GP. Availability varies significantly by region, and waiting lists can be lengthy. Private access: Online consultation with a UK-licensed prescriber, prescription issued if clinically appropriate, dispensed by a GPhC-registered pharmacy. No NHS referral needed, but costs typically range from £129–£320 per month depending on dose.
The first step is to speak to your GP about whether prescription weight loss medication might be suitable for you. Your GP can assess your individual health, discuss your weight loss goals, and explain options available in your area. Remember, prescription medications work best alongside dietary changes and increased physical activity — use our free weight loss calculator to project potential outcomes with GLP-1 medication.
- 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 thyroid vitamins help with weight loss?
Thyroid vitamins like selenium and zinc support thyroid function, which affects metabolism. If you have a thyroid deficiency, treating it can help normalise weight. However, for many people, thyroid function is normal, and weight loss requires dietary changes or prescription medication. Speak to your GP to check your thyroid if you suspect it's affecting your weight.
What's the difference between Mounjaro and Wegovy for weight loss?
Mounjaro (tirzepatide) is a dual GIP and GLP-1 receptor agonist with average weight loss around 15–21%. Wegovy (semaglutide) is a GLP-1 agonist with average weight loss around 15%. Both are once-weekly injections. Individual results vary significantly. Your prescriber will recommend the most suitable option based on your health.
How do I know if I'm eligible for prescription weight loss medication in the UK?
You may be eligible if your BMI is 30 or above, or 27–29.9 with weight-related health conditions such as diabetes or high blood pressure. Lower thresholds apply if you're of South Asian, Chinese, Black African, or Black Caribbean heritage. Use our BMI calculator to check your BMI, then speak to your GP about eligibility.
How much weight can I expect to lose with Mounjaro or Wegovy?
In clinical trials, people using these medications lost an average of 15–21% of their body weight over several months. However, individual results vary significantly. Weight loss depends on your starting weight, dose, diet, and physical activity. Our weight loss calculator can help you estimate potential outcomes.
Can I get prescription weight loss medication through the NHS?
Yes, the NHS does provide access to prescription weight loss medication through specialist tier 3 weight management services. You'll need a GP referral. Availability and waiting times vary by region. Private access is also available through online prescribers without an NHS referral, though there is a cost involved.
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.