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 Diet Charts and Weight Loss Medication in the UK
If you're a woman managing thyroid health and weight loss, you may be wondering whether prescription medication could support your goals alongside dietary changes. While thyroid-specific diet charts can help with managing symptoms, the UK has several licensed weight management medications available for eligible adults. This guide explores how prescription options like Mounjaro and Wegovy fit alongside lifestyle approaches, and how to find out if you qualify for NHS or private support.
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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 Management Medication Options
For women eligible for weight management medication in the UK, three prescription-only options are currently available:
- Mounjaro (tirzepatide) — a dual GIP and GLP-1 injection taken once weekly, with an average clinical trial weight loss of 15–21% body weight
- Wegovy (semaglutide) — a GLP-1 injection taken once weekly, supporting approximately 15% average weight loss in clinical trials
- Saxenda (liraglutide) — a GLP-1 injection taken daily, approved for weight management in eligible adults
Eligibility generally requires a BMI of 30 or above, or 27 or above with weight-related health conditions. Individual results vary, and these medications work best alongside a reduced-calorie diet and increased physical activity. You can calculate your personal BMI using our free BMI calculator to see where you stand, and our GLP-1 weight loss calculator can help estimate potential outcomes at different doses if you were to become eligible.
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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 and Next Steps
Access to prescription weight management medication in the UK differs between NHS and private routes. NHS access is through tier 3 specialist weight management services — your GP can refer you, though waiting lists vary significantly by region and can be lengthy. Private access is available through GPhC-registered online pharmacies following a clinical assessment with a UK-licensed prescriber, typically without NHS referral.
The best first step is to speak with your GP about your weight management goals and thyroid health. They can assess whether prescription medication is appropriate for you, discuss eligibility, and explain both NHS and private options available in your area. Your GP can also ensure any medication is safe alongside your thyroid 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 I take weight loss medication if I have a thyroid condition?
Possibly, but it requires individual assessment. You must inform your GP or prescriber about your thyroid condition and any medications you take (including thyroid replacement). Some people with thyroid issues are eligible for prescription weight management medication, but suitability depends on your specific health profile. Your GP can advise whether medication is safe for you.
How much weight will I lose on GLP-1 medication?
Clinical trials show average weight loss of 15–21% body weight with Mounjaro and around 15% with Wegovy, but individual results vary significantly. Some people lose more, others less. Results depend on dose, adherence to diet and exercise changes, and individual factors. Our free GLP-1 weight loss calculator can give you a rough estimate based on current clinical trial data.
What is the difference between Mounjaro and Wegovy?
Mounjaro (tirzepatide) is a dual GIP and GLP-1 receptor agonist taken once weekly, whilst Wegovy (semaglutide) is a GLP-1 agonist only, also taken once weekly. Clinical trial data suggests slightly higher average weight loss with Mounjaro, but both are effective. Your prescriber will assess which is most suitable for you based on your health profile.
How do I know if I'm eligible for prescription weight loss medication?
You're generally eligible if you have a BMI of 30 or above, or 27–29.9 with weight-related health conditions such as type 2 diabetes, hypertension, or cardiovascular disease. Use our free BMI calculator to check your current BMI. Your GP or a licensed prescriber will perform a full clinical assessment to confirm eligibility and safety for you personally.
Can I get weight loss medication through the NHS?
Yes, but access is through specialist tier 3 weight management services, not standard GP prescription. Ask your GP for a referral to your local specialist weight management service. Alternatively, prescription weight loss medication is available privately through GPhC-registered online pharmacies following clinical assessment. Availability and waiting times vary significantly by region.
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.