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 Medication for Rheumatoid Arthritis in the UK
Living with rheumatoid arthritis (RA) can make weight management challenging, especially if mobility is limited or if certain medications affect appetite and metabolism. If you have RA and are overweight or living with obesity, prescription weight loss medication may be an option worth discussing with your GP. The NHS now offers several licensed weight management treatments that can support sustainable weight loss alongside your existing RA care. This guide explains what's available in the UK and how to find out if you're eligible.
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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 RA
Three prescription-only weight loss medications are currently licensed in the UK and may be suitable if you have RA and meet eligibility criteria:
- Mounjaro (tirzepatide) — a once-weekly injection that activates GLP-1 and GIP pathways, helping regulate appetite and support feeling fuller after meals. Clinical trials showed average weight loss of 15–21% of body weight over 72 weeks.
- Wegovy (semaglutide) — a once-weekly GLP-1 injection. STEP trials showed average weight loss of approximately 14.9% of body weight over 68 weeks alongside reduced-calorie diet and increased activity.
- Saxenda (liraglutide) — a daily GLP-1 injection, slightly different dosing but similar mechanism to Wegovy.
All three require a clinical assessment before prescription. Your GP or prescriber will check whether you're eligible based on BMI and health factors, and whether the medication is safe alongside your RA treatments — important because some weight loss medications may interact with immunosuppressants or other RA therapies.
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 Access vs Private — How to Start
NHS route: Your GP can refer you to a specialist tier 3 weight management service if you meet criteria (BMI 30+, or 27–29.9 with health conditions like RA). NHS availability varies by region, and waiting lists can be long. Some ICBs now cover tirzepatide (Mounjaro) and semaglutide (Wegovy) through specialist services, but access is not uniform across the UK.
Private route: If NHS waiting times are prohibitive, GPhC-registered online pharmacies offer weight loss medication following an online consultation with a UK-licensed prescriber. This can be faster but involves out-of-pocket cost.
Your next step: Book a conversation with your GP about weight loss medication. Bring your BMI and describe how weight affects your RA symptoms (e.g., joint strain, mobility). Your GP can advise on NHS eligibility or signpost you to private options. Always use our free BMI calculator to know your starting point before the appointment.
- 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 I take weight loss injections if I have rheumatoid arthritis?
Possibly, but it depends on your specific RA medications and overall health. Some weight loss medications may interact with immunosuppressants used in RA treatment. Your GP or rheumatologist must assess safety before prescribing. Never start any new medication without informing your healthcare team about your RA diagnosis and current drugs.
Will losing weight help my rheumatoid arthritis symptoms?
Evidence suggests that losing weight can reduce joint stress and inflammation burden, potentially easing RA symptoms. Even modest weight loss (5–10% of body weight) may improve pain and mobility. However, weight loss doesn't replace RA medication — it complements your existing treatment plan.
How much weight can I expect to lose with prescription medication?
Clinical trials show average weight loss of 15–21% of body weight with Mounjaro and around 14.9% with Wegovy over several months. However, individual results vary significantly. Weight loss occurs alongside a reduced-calorie diet and increased physical activity — medication alone is not effective without lifestyle changes.
Is prescription weight loss medication available on the NHS for RA patients?
Yes, if you meet eligibility criteria (BMI 30+, or 27–29.9 with weight-related health conditions like RA). You'll need to be referred to a specialist tier 3 weight management service by your GP. Availability and waiting times vary across UK regions.
What's the difference between Mounjaro and Wegovy?
Both are once-weekly injections, but Mounjaro (tirzepatide) activates two hormone pathways (GIP and GLP-1), while Wegovy (semaglutide) activates GLP-1 only. Clinical data suggests Mounjaro may produce slightly higher average weight loss, but individual responses vary. Your prescriber will recommend the most suitable option based on your health profile.
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.