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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RA and Weight Loss — Medication Options in the UK
Rheumatoid arthritis (RA) can make weight management challenging due to inflammation, reduced mobility, and medication side effects. If you're living with RA and looking to lose weight, prescription weight management options are available through the NHS and private prescribing in the UK. These medications may help alongside lifestyle changes, particularly if you meet eligibility criteria. It's important to discuss weight management with your GP or rheumatology team, as they can assess what's safe for your individual health situation.
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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 medications are currently licensed for weight management in the UK and may be suitable for people with RA, depending on individual circumstances:
- Mounjaro (tirzepatide) — a once-weekly injection that works as a dual GIP and GLP-1 receptor agonist. Clinical trials showed an average weight loss of 15–21% body weight alongside reduced-calorie diet and increased physical activity.
- Wegovy (semaglutide) — a once-weekly GLP-1 injection. Average weight loss in trials was approximately 15% body weight.
- Saxenda (liraglutide) — a daily GLP-1 injection, typically prescribed when weekly options are unsuitable.
You're eligible if you have a BMI of 30 or above, or 27 or above with weight-related health conditions. Your prescriber will assess whether medication is appropriate alongside your RA management. Use our free GLP-1 weight loss calculator to explore potential outcomes at different doses — though individual results vary significantly.
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 and Getting Started
NHS access: Weight loss medications are available through specialist tier 3 weight management services by GP referral. Availability and waiting times vary significantly by region. Your GP or rheumatology team can refer you if you meet eligibility criteria.
Private access: Available through UK-licensed online prescribers following a clinical assessment, without NHS referral. Costs typically range from £129–£320 monthly depending on dose.
Both routes require a full health assessment to confirm suitability. Be honest about your RA diagnosis and current medications — your prescriber needs this information to ensure safety. Calculate your BMI using our free BMI calculator to understand your starting point before speaking with your GP.
- 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 RA?
Weight loss medications like Mounjaro and Wegovy may be suitable for people with RA, but your individual circumstances matter. Your GP or rheumatology team must assess whether it's safe alongside your current RA treatments and other medications. Inform any prescriber about your RA diagnosis. Some people with RA benefit from weight loss to reduce joint stress.
Will weight loss help my RA symptoms?
Modest weight loss (even 5–10% of body weight) may help reduce stress on joints, potentially easing RA symptoms. However, weight loss is not a treatment for RA itself — it's a complementary approach. Your rheumatology team remains your primary source for RA management. Weight management should work alongside your existing RA medication.
What weight management options are available on the NHS for RA?
The NHS offers tier 3 specialist weight management services available by GP referral. Prescription medications like Mounjaro, Wegovy, and Saxenda are available through these services for eligible adults. However, availability and waiting times vary significantly by region. Ask your GP about local services and whether you might be eligible.
How do GLP-1 weight loss injections work?
GLP-1 medications like Wegovy activate the GLP-1 hormone pathway to reduce appetite, increase fullness, and support feeling satisfied after smaller meals. They work best alongside a reduced-calorie diet and increased physical activity. Individual responses vary. They do not replace RA treatment and are a separate weight management tool.
Are weight loss injections safe alongside RA medication?
Safety depends on your specific RA medications and overall health. Your prescriber will review all your medications during the clinical assessment. Some RA drugs may interact with weight loss injections, or your prescriber might need to monitor you more closely. Always disclose your complete medical history and all current medications.
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.