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 Plan & Weight Loss — UK Medication Options
A thyroid diet plan can support weight loss, but for some people in the UK, prescription weight management medication may also help. This guide explains how thyroid health affects weight, dietary approaches, and the prescription weight loss options available to eligible adults through NHS weight loss services or private prescribing. We'll help you understand what's available and how to find out if you qualify for treatment that could support your weight management journey alongside lifestyle changes.
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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 Prescription Weight Loss Options for Weight Management
Several prescription weight loss medications are licensed in the UK for adults with excess weight. The main options include Mounjaro (tirzepatide), a dual GIP and GLP-1 receptor agonist, Wegovy (semaglutide), a GLP-1 agonist, and Saxenda (liraglutide), also a GLP-1 agonist. Clinical evidence shows these medications may help reduce appetite and support weight management when combined with dietary changes and increased physical activity. In clinical trials, eligible adults lost an average of 15–21% of their body weight over several months, though individual results vary significantly. These are prescription-only medicines requiring assessment by a licensed prescriber to confirm suitability based on your personal health profile, BMI, and any weight-related health conditions.
Eligibility typically includes adults with a BMI of 30 or above, or 27 or above if you have weight-related conditions such as type 2 diabetes, high blood pressure, or sleep apnoea. Use our free BMI calculator to check your personal BMI and understand where you fall on NHS weight categories, which is the first step in assessing potential eligibility for prescription weight management support.
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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 to Weight Loss Medication
NHS route: Weight loss medication is available through specialist tier 3 weight management services, usually following referral from your GP. Access and waiting times vary significantly by region and ICB (integrated care board). Some areas have substantial waiting lists.
Private route: Prescription weight loss medication is available through GPhC-registered online pharmacies after a consultation with a UK-licensed prescriber. This route typically offers faster access without NHS referral. Your GP can still provide support and monitoring alongside private treatment. Either way, medication works best alongside a reduced-calorie diet and increased physical activity—consider tracking your progress using our free progress tracker to monitor weight changes over time.
Q1: Can a thyroid diet plan alone help with weight loss? A1: Yes, dietary changes can support weight loss, especially if thyroid function is optimised. A balanced diet lower in processed foods and higher in whole grains, lean protein, and vegetables supports general health. However, if thyroid medication dosage is suboptimal, weight loss may be harder to achieve through diet alone. Your GP can check your thyroid levels and ensure your medication is properly adjusted. For those who need additional support, prescription weight loss medication may be appropriate. Q2: Who is eligible for NHS weight loss medication in the UK? A2: Adults with a BMI of 30 kg/m² or above, or 27–29.9 with weight-related health conditions (type 2 diabetes, high blood pressure, sleep apnoea), may be eligible. Eligibility varies by NHS region. Your GP can assess whether you meet the criteria for referral to specialist weight management services. Use our free BMI calculator to check your starting point, then discuss options with your GP. Q3: How much weight can I expect to lose with prescription medication? A3: Clinical trials show average weight loss of 15–21% of body weight over several months, depending on the medication and dose. However, individual results vary significantly—some people lose more, some less. Results depend on medication adherence, dietary changes, physical activity level, genetics, and metabolism. Weight loss medication works best as part of a comprehensive approach including lifestyle changes, not as a standalone treatment. Q4: What's the difference between Mounjaro and Wegovy for weight loss? A4: Both are prescription-only injections administered once weekly. Mounjaro (tirzepatide) is a dual GIP and GLP-1 agonist; Wegovy (semaglutide) is a GLP-1 agonist only. Clinical evidence suggests Mounjaro may produce slightly greater average weight loss (15–21% vs approximately 15%), though results vary. Your prescriber will assess which is more suitable based on your health profile. Try our GLP-1 weight loss calculator to explore potential outcomes at different doses. Q5: Can I access weight loss medication without NHS referral? A5: Yes. Prescription weight loss medication is available privately through online consultations with UK-licensed prescribers, followed by dispensing through GPhC-registered pharmacies. This route doesn't require NHS referral but does require a valid prescription and clinical assessment. Private costs typically range from £129–£320+ monthly depending on medication and dose. Many people combine private medication with NHS GP monitoring for ongoing health support.- 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.
What is BMI and how is it calculated?
BMI (Body Mass Index) is calculated by dividing your weight in kilograms by your height in metres squared. It's the standard screening tool used by the NHS to assess whether adults are a healthy weight.
Is BMI accurate for everyone?
BMI is a useful screening tool but doesn't account for muscle mass, bone density, or body fat distribution. Athletes may have a high BMI without excess fat. The NHS recommends using BMI alongside waist circumference for a more complete picture.
What are GLP-1 medications like Mounjaro and Wegovy?
GLP-1 receptor agonists are prescription medications that mimic gut hormones to reduce appetite and help with weight loss. Mounjaro (tirzepatide) and Wegovy (semaglutide) are the two most widely used for weight management in the UK.
Am I eligible for GLP-1 weight loss medication in the UK?
Generally, you need a BMI of 30+ (obese) or 27+ with a weight-related health condition. You must be 18 or over. Use our BMI calculator to check.
What is the difference between Mounjaro and Wegovy?
Mounjaro (tirzepatide) is a dual GIP/GLP-1 agonist with up to 22.5% weight loss. Wegovy (semaglutide) is GLP-1-only with up to 15-17% weight loss. Both are weekly injections.
Is this website free to use?
Yes, 100% free. No sign-up required. All tools work instantly in your browser and no personal data is stored on our servers.
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.