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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Weight Management After Thyroidectomy in the UK
After thyroidectomy, many people find weight management more challenging due to changes in metabolism and thyroid hormone replacement. If you're struggling with weight loss in the UK, prescription weight management options are available. This guide explains NHS-approved medications, eligibility criteria, and how to access support through your GP or private prescribers. You can also use our free BMI calculator to track where you currently sit on the NHS health scale and monitor progress over time.
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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 Options
Three prescription-only weight loss medications are currently licensed in the UK: Mounjaro (tirzepatide), Wegovy (semaglutide), and Saxenda (liraglutide). These work by activating GLP-1 pathways (or dual GLP-1/GIP pathways in Mounjaro's case) to help reduce appetite, support feeling fuller after meals, and assist weight management alongside diet and physical activity.
- Mounjaro: Once-weekly injection, doses 2.5–15mg, average clinical trial weight loss 15–21% of body weight
- Wegovy: Once-weekly injection, doses 0.25–2.4mg, average clinical trial weight loss approximately 15% of body weight
- Saxenda: Daily injection, doses 0.6–3mg, established GLP-1 option with long track record
Eligibility typically requires a BMI of 30 or above, or 27+ with weight-related health conditions such as type 2 diabetes or cardiovascular concerns. Post-thyroidectomy weight gain may qualify you. Individual results vary, and all three medications require a clinical assessment before prescription.
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.
Accessing Weight Loss Medication: NHS vs Private Routes
NHS route: Speak with your GP about referral to a specialist tier 3 weight management service. NHS access to prescription weight loss medications is available but varies significantly by region and waiting times can be lengthy. Your GP can assess your eligibility and discuss whether medication is appropriate alongside your thyroid hormone replacement management.
Private route: UK-licensed prescribers offer online consultations and prescription services without NHS referral. Following a clinical assessment, medication can be dispensed by GPhC-registered pharmacies. Costs typically range from £129–£320 monthly depending on dose and provider.
Try our free GLP-1 weight loss calculator to explore how different medication doses might support your goals, and use our weight converter to track measurements in kg, stone, and lbs.
- 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've had a thyroidectomy?
Yes, if you meet NHS eligibility criteria (BMI ≥30 or ≥27 with health conditions), you can be assessed for prescription weight loss medication. Your GP needs to know about your thyroidectomy history to ensure your thyroid hormone replacement is stable. Always inform any prescriber about your thyroidectomy and current levothyroxine dose.
How does thyroidectomy affect weight loss efforts?
After thyroidectomy, metabolism may slow and weight management becomes harder. Proper levothyroxine replacement helps, but many people still struggle. This is where lifestyle changes and, if eligible, prescription weight management medication can provide additional support alongside good thyroid hormone control.
Will weight loss medication interact with my thyroid medication?
GLP-1 medications may slow stomach emptying, which could theoretically affect levothyroxine absorption. Always take levothyroxine on an empty stomach as directed, separate from other medications. Discuss timing with your GP or prescriber to ensure your thyroid hormone levels remain stable.
How long does it take to see weight loss results with prescription medication?
Results vary, but most people see noticeable changes within 8–12 weeks of starting or increasing doses. Weight loss is gradual and sustainable when combined with reduced-calorie diet and increased physical activity. Your GP can monitor your progress.
What's the difference between Mounjaro and Wegovy for weight loss?
Mounjaro is a dual GIP/GLP-1 agonist (doses 2.5–15mg weekly), whilst Wegovy is GLP-1 only (0.25–2.4mg weekly). Clinical trials suggest Mounjaro may have a slight edge in average weight loss, but individual results vary significantly. Your prescriber will recommend the most suitable option based on your health profile.
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.