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 Loss with Rheumatoid Arthritis — A UK Health Guide
Rheumatoid arthritis (RA) can make weight management particularly challenging due to inflammation, reduced mobility, and medication effects. If you have RA and are looking to lose weight or understand your weight in relation to your health, this guide explains how RA affects weight, what support is available through the NHS, and how to approach weight management safely alongside your treatment. Using our free BMI calculator above can help you understand your current weight status and set realistic health goals.
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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 RA Affects Weight and Weight Management
Rheumatoid arthritis creates unique challenges for weight management. Inflammation and joint pain often reduce physical activity levels, making it harder to burn calories and maintain muscle mass. Some RA medications — particularly corticosteroids like prednisolone — can increase appetite and promote weight gain, especially around the abdomen. Additionally, fatigue is a common RA symptom that can reduce motivation for exercise and healthy eating.
- Reduced mobility due to joint pain limits physical activity and calorie burning
- Corticosteroids and other DMARDs may affect appetite and metabolism
- Chronic inflammation increases energy demands but also increases fatigue
- Weight gain itself can increase stress on affected joints, worsening symptoms
This creates a difficult cycle: excess weight increases joint stress and inflammation, while the RA itself makes weight loss harder. Managing weight can actually help reduce RA symptoms and improve overall health outcomes. Your GP or rheumatology team can provide personalised advice about weight management alongside your RA treatment.
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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 Weight Loss Support for RA Patients
The NHS offers weight management support specifically for people with chronic conditions like rheumatoid arthritis. Your GP can refer you to tier 2 or tier 3 weight management services, which provide specialist support tailored to your individual circumstances. These services take into account your RA, current medications, mobility limitations, and any other health conditions.
If your BMI is in the overweight or obese range (above 25 for most adults, or above 23 for people of South Asian heritage), your GP may recommend structured support. This might include dietetic advice, behaviour change programmes, or — if appropriate — assessment for prescription weight loss medication. Prescription weight loss treatments like GLP-1 injections (Wegovy or Mounjaro) may be considered for eligible patients, though individual assessment is essential. Our GLP-1 weight loss calculator can help you understand potential weight loss trajectories if medication is being considered.
- 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.
Does rheumatoid arthritis make weight loss harder?
Yes. RA reduces mobility due to joint pain and fatigue, limiting physical activity. Many RA medications, especially corticosteroids, can increase appetite and affect metabolism. However, weight loss is still achievable with appropriate support, dietary adjustments, and sometimes medication to help manage appetite.
Can I use weight loss injections if I have rheumatoid arthritis?
Potentially, yes — but this requires individual assessment by your GP or rheumatology team. GLP-1 medications like Wegovy are prescription-only and eligibility depends on your BMI, overall health, current RA medications, and any interactions. Always discuss this with your healthcare provider before starting any new treatment.
What's a safe rate of weight loss when you have RA?
The NHS recommends losing 0.5 to 1 kg per week for sustainable results. This is especially important with RA because gradual weight management can lead to muscle loss, which may worsen joint stability. Work with your GP or a dietitian to find a pace that works for your condition.
How do RA medications affect weight?
Corticosteroids (like prednisolone) commonly increase appetite and cause weight gain. Some DMARDs and biologic medications have less effect on weight. Your rheumatology team can discuss medication options and their effects with you. Never stop or change your RA medication without medical advice.
Should I use the BMI calculator if I have RA and limited mobility?
Yes — BMI is still a useful screening tool for people with RA. However, discuss your individual weight health with your GP, as they'll consider your mobility, muscle strength, inflammation levels, and overall fitness alongside your BMI.
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.