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
Free tracker included with every download this week
Arthritis and Weight Loss in the UK
Extra weight places additional strain on joints, often making arthritis pain worse. Losing weight can significantly reduce joint stress and improve mobility, particularly for osteoarthritis sufferers. The good news is that prescription weight management medication is now available in the UK for eligible adults. This guide explains how weight loss helps arthritis, the UK-licensed options available, and how to find out if you're eligible for treatment through the NHS or privately.
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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 Prescription Weight Loss Options for Arthritis
For adults struggling with both arthritis and excess weight, prescription weight loss medication may help alongside lifestyle changes. Three GLP-1 medications are currently licensed in the UK for weight management:
- Mounjaro (tirzepatide) — dual GIP and GLP-1 receptor agonist, once-weekly injection, doses 2.5 mg to 15 mg
- Wegovy (semaglutide) — GLP-1 receptor agonist, once-weekly injection, doses 0.25 mg to 2.4 mg
- Saxenda (liraglutide) — GLP-1 receptor agonist, once-daily injection, doses 0.6 mg to 3 mg
Clinical trials show these medications help achieve average weight loss of 15–21% of body weight when combined with a reduced-calorie diet and increased physical activity. Individual results vary significantly. You must be assessed by a licensed prescriber before starting any weight loss medication. Eligibility typically requires a BMI of 30 or above, or BMI 27–29.9 with weight-related health conditions — and arthritis-related mobility limitations may be considered as a relevant comorbidity.
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.
NHS vs Private Access to Weight Loss Medication
NHS route: Weight loss medication is available through specialist tier 3 weight management services, accessed via GP referral. However, availability varies significantly by region and waiting lists can be lengthy — in some areas, several months to over a year. Ask your GP about local NHS weight management services and referral pathways.
Private route: Prescription weight loss medication is available through GPhC-registered online pharmacies following a clinical assessment with a UK-licensed prescriber. Access is faster and does not require NHS referral. Costs typically range from £129–£320 per month depending on dose and provider. Both routes require a prescription from a licensed healthcare professional who will assess your individual health, medications, and suitability.
- 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 weight loss medication help my arthritis?
Weight loss of even 5–10% of body weight can significantly reduce joint pain and improve mobility in arthritis sufferers, particularly with osteoarthritis. Prescription weight loss medication may help you achieve this alongside diet and exercise, but medication is a tool to support lifestyle change, not a replacement for it.
Am I eligible for weight loss medication on the NHS?
Generally, yes, if you have a BMI of 30 or above, or 27–29.9 with weight-related health conditions. Arthritis-related mobility issues or other comorbidities may strengthen your eligibility. Contact your GP for an assessment and referral to your local NHS weight management service.
How much weight can I expect to lose with Mounjaro or Wegovy?
Clinical trials show average weight loss of 15–21% of body weight over several months, but individual results vary considerably. Some people lose more, some less. Results depend on your starting weight, adherence to a reduced-calorie diet, physical activity level, and individual metabolism.
What are the main side effects of weight loss injections?
Common side effects include nausea, diarrhoea, constipation, and stomach pain — usually mild and temporary as your body adjusts. Less common side effects include vomiting, indigestion, and injection site reactions. Speak to your prescriber about managing side effects and when to seek medical attention.
How do I check my BMI and if I'm a suitable weight for medication?
Use our free BMI calculator above to check your personal BMI instantly. If your BMI is in the overweight or obese range and you have joint pain or arthritis, use our GLP-1 weight loss calculator to explore potential outcomes, then discuss your results with your GP to discuss prescription options and referral.
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.