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 — How Weight Loss May Help
Excess weight places significant strain on joints, particularly in the knees, hips, and lower back, which can worsen arthritis symptoms and pain. Mounjaro (tirzepatide) is a prescription weight loss injection licensed in the UK that may help reduce body weight, potentially easing joint stress and arthritis discomfort. This guide explains how Mounjaro works, whether you might be eligible, costs in the UK, and how to access it through NHS or private prescription routes. Always discuss any changes to your weight management or arthritis treatment with your GP first.
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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.
How Weight Loss Can Support Arthritis Management
Arthritis—both osteoarthritis and rheumatoid arthritis—affects millions of UK adults and causes pain, stiffness, and reduced mobility. Research shows that excess weight significantly increases stress on weight-bearing joints, particularly knees, hips, ankles, and the lower back.
- Every 1 kg of excess weight adds approximately 4 kg of force across the knee joint when walking
- Even a 5–10% reduction in body weight can meaningfully reduce arthritis pain and improve joint function
- Weight loss combined with appropriate arthritis treatment (medication, physiotherapy, exercise) often produces better outcomes than either alone
Mounjaro is a dual GIP and GLP-1 receptor agonist that works by regulating appetite hormones and supporting a feeling of fullness. When combined with reduced-calorie diet and physical activity, tirzepatide (the active ingredient in Mounjaro) has helped adults lose an average of 15–21% of body weight in clinical trials—though individual results vary. For people with arthritis seeking weight management support, Mounjaro may be an option worth discussing with your GP, particularly if lifestyle changes alone have not been effective.
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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.
Mounjaro Access and Costs in the UK
NHS access: Mounjaro is approved by NICE for use within NHS specialist tier 3 weight management services. However, NHS access is limited and varies significantly by region. Your GP can refer you to your local specialist weight management service, though waiting lists can extend several months or longer depending on availability in your area.
Private access: Private prescription Mounjaro is available through UK-licensed prescribers via online consultation, typically costing £130–£320 per month depending on your dose (starting dose 2.5 mg, titrating up to 15 mg maximum). Private prescriptions are dispensed by GPhC-registered pharmacies without requiring an NHS referral. The online assessment process usually takes 24–48 hours.
Whichever route you choose, a prescriber will assess your eligibility based on your BMI, health conditions, and current medications before issuing a prescription. Use our free GLP-1 weight loss calculator to estimate potential weight loss outcomes at different Mounjaro doses alongside a reduced-calorie diet.
UK eligibility: You may be eligible for Mounjaro if you have a BMI of 30 or above, or 27–29.9 with weight-related health conditions (including arthritis). South Asian, Chinese, Black African, and Black Caribbean adults may have lower BMI eligibility thresholds (from BMI 27.5). You cannot take Mounjaro if you are under 18, pregnant, breastfeeding, or have a personal or family history of medullary thyroid cancer.
Mounjaro vs Wegovy: Both are once-weekly weight loss injections licensed in the UK. Mounjaro uses a dual GIP+GLP-1 mechanism and showed slightly higher average weight loss (15–21% vs approximately 15% for Wegovy) in clinical trials. Choice between them depends on your prescriber's assessment and individual response. Check your BMI using our free BMI calculator to confirm whether you fall into the eligibility range.
- 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.
Will Mounjaro supports my arthritis?
No. Mounjaro is not an arthritis treatment—it is a weight loss medication. However, reducing excess weight through Mounjaro, combined with your existing arthritis treatment (medication, physiotherapy, exercise), may help reduce joint pain and improve mobility. Always continue taking prescribed arthritis medications and consult your rheumatologist or GP before starting Mounjaro.
How much weight do I need to lose to feel arthritis pain relief?
Clinical evidence suggests that losing even 5–10% of body weight can meaningfully reduce arthritis symptoms and joint stress. A greater loss (15–20%+) typically produces more noticeable improvement. Individual results vary depending on which joints are affected, type of arthritis, and overall health. Your GP can discuss realistic expectations for your situation.
Can I take Mounjaro if I'm on arthritis medications?
Mounjaro can be used alongside most arthritis medications (NSAIDs, biologics, steroids, DMARDs). However, Mounjaro may slow absorption of oral medications taken at the same time. Your prescriber will review all your medications before issuing a prescription and advise on timing if necessary. Always disclose all current medications when applying for Mounjaro.
How quickly will I lose weight on Mounjaro?
Weight loss timing varies by individual. Most people begin losing weight within 2–4 weeks of starting. Mounjaro is given as once-weekly injections with a dose titration schedule—your dose increases gradually over 16–20 weeks to reach your target maintenance dose. Total weight loss builds over months, with maximum results typically seen at 12+ months. Sustained weight loss requires ongoing use alongside diet and activity changes.
Is Mounjaro available on the NHS for arthritis-related weight loss?
Mounjaro is available on the NHS through specialist tier 3 weight management services if you meet eligibility criteria (BMI ≥30, or ≥27 with weight-related health conditions). Arthritis alone does not automatically grant priority—access depends on your BMI, other health factors, and regional availability. Your GP can refer you; private prescription is an alternative if NHS waiting times are lengthy in your area.
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.