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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Mounjaro and Arthritis — What You Need to Know
Many people with arthritis wonder whether prescription weight loss medication could help their joint pain. Mounjaro (tirzepatide) is a once-weekly GLP-1 and GIP receptor agonist injection licensed for weight management in UK adults. Because excess weight increases stress on joints and can worsen arthritis symptoms, losing weight may help reduce pain and improve mobility. This guide explains how Mounjaro works, how weight loss may benefit arthritis, and what the NHS says about eligibility for this prescription medication in the UK.
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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.
How Weight Loss May Help Arthritis Symptoms
Osteoarthritis develops when cartilage in joints wears down, and excess weight increases the load on weight-bearing joints like knees, hips, and ankles. Research consistently shows that losing even 5–10% of body weight can reduce joint pain, improve mobility, and lower inflammation markers in the body. When taking a GLP-1 medication like Mounjaro (tirzepatide), weight loss typically occurs through reduced appetite and feeling fuller after smaller meals. In clinical trials, participants on the maximum 15 mg dose lost an average of around 20.9% of their body weight over 72 weeks, though individual results vary. Alongside dietary changes and increased physical activity, this weight loss may ease pressure on joints. If you have arthritis and are overweight or obese, your GP may refer you to an NHS tier 3 specialist weight management service, where Mounjaro eligibility can be assessed. Use our free BMI calculator above to check your current BMI and understand your starting point for weight loss.
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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.
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NHS Eligibility and Important Considerations
NHS access: Mounjaro is available through NHS tier 3 specialist weight management services for adults with a BMI of 30 or above, or 27–29.9 with weight-related health conditions (which may include arthritis complications). However, NHS availability varies significantly by region, and waiting lists can be lengthy. Important: Mounjaro is prescription-only and requires a clinical assessment before being prescribed. It is not recommended during pregnancy or whilst breastfeeding. Common side effects include nausea, diarrhoea, and stomach discomfort—typically temporary and manageable. If you have severe arthritis or are taking specific medications, your prescriber will assess suitability. Discuss with your GP whether specialist weight management services in your area may be appropriate for you.
- 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 Mounjaro directly treat arthritis?
No. Mounjaro is a weight loss medication that works by reducing appetite. It does not directly treat arthritis. However, by supporting weight loss, it may reduce stress on joints and potentially ease arthritis symptoms. Always discuss joint pain with your GP before starting any weight loss treatment.
What does the NHS say about weight loss and arthritis?
The NHS recognises that excess weight worsens osteoarthritis and recommends weight management as part of arthritis care. A 5–10% reduction in body weight can significantly reduce joint pain and improve mobility. Your GP can advise whether specialist weight management services are appropriate for you.
How quickly might arthritis symptoms improve with Mounjaro?
Weight loss typically begins within 4–8 weeks, but significant joint pain improvement usually takes several months as cartilage adjusts to reduced load. Results vary between individuals. Some people notice improved mobility within 12 weeks; others take longer. Consistent lifestyle changes alongside any medication are important.
What are the side effects of Mounjaro, and could they affect arthritis?
Common side effects include nausea, diarrhoea, and stomach pain—usually temporary. These are unlikely to directly worsen arthritis, but if you experience severe joint pain alongside medication side effects, contact your GP. Staying hydrated and eating small, frequent meals can help manage gastrointestinal effects.
Is Mounjaro available on the NHS for weight loss related to arthritis?
Mounjaro is available through NHS tier 3 specialist weight management services for eligible adults. Arthritis alone is not an automatic eligibility criterion, but if you have arthritis and meet BMI thresholds (30+, or 27–29.9 with comorbidities), you may qualify. Availability varies by region. Ask your GP for a referral to local services.
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.