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, Fibromyalgia, and Weight Management in the UK
Fibromyalgia is a long-term pain condition that affects millions of UK adults, and weight management can play an important role in symptom management. Mounjaro (tirzepatide) is a prescription-only injection approved for weight management in the UK, but it is not specifically approved to treat fibromyalgia itself. However, losing weight may help reduce pain and improve quality of life for people with fibromyalgia. If you're considering Mounjaro alongside fibromyalgia management, understanding how it works and what NHS support is available is essential. This guide explains the UK context, eligibility criteria, and how to discuss weight management with your NHS team.
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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 Relates to Fibromyalgia and Mounjaro's Role
Fibromyalgia causes widespread musculoskeletal pain, fatigue, and sleep disturbance, and it often co-exists with weight gain. Research shows that even modest weight loss—5 to 10% of body weight—can reduce fibromyalgia pain intensity, improve mobility, and decrease fatigue in some patients. This is why NHS specialists view weight management as part of holistic fibromyalgia care.
Mounjaro (tirzepatide) is a GIP and GLP-1 receptor agonist—meaning it works through two natural hormone pathways to help reduce appetite and support weight loss. In clinical trials, patients on Mounjaro lost an average of 15 to 21% of their body weight over 72 weeks, though individual results vary significantly. For fibromyalgia patients, weight loss via Mounjaro might help ease joint stress and improve symptom control, but Mounjaro itself does not treat fibromyalgia pain or fatigue.
If you're overweight or obese (BMI 30+) or overweight with fibromyalgia-related health complications (high blood pressure, sleep apnoea), you may be eligible for prescription weight loss treatment through NHS tier 3 specialist services or via private prescribing following clinical assessment.
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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 Eligibility and Accessing Mounjaro in the UK
On the NHS, Mounjaro is available through specialist tier 3 weight management services, not from your GP directly. You'll typically need referral from your GP to these services, though availability varies significantly by region and ICB (Integrated Care Board). Waiting lists can be lengthy—sometimes 12+ months in some areas.
To be eligible, you must have a BMI of 30 or above, or BMI 27–29.9 with weight-related health conditions. For fibromyalgia patients, sleep apnoea, high blood pressure, or reduced mobility from pain may qualify as comorbidities. Once referred and assessed by the specialist team, they will evaluate whether Mounjaro is clinically appropriate for you, considering your fibromyalgia management and other medications.
Alternatively, private prescribing through a GPhC-registered online service can provide faster access following an online clinical assessment—typically within days rather than months.
- 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 Mounjaro treat fibromyalgia pain?
No. Mounjaro (tirzepatide) is approved for weight management only, not fibromyalgia treatment. However, losing weight through Mounjaro may help reduce pain severity and improve mobility by decreasing joint stress—which is why weight management is recommended as part of overall fibromyalgia care in the NHS guidelines.
Am I eligible for Mounjaro if I have fibromyalgia?
You may be eligible if you have a BMI of 30+ or BMI 27–29.9 with weight-related health conditions. For fibromyalgia patients, conditions like sleep apnoea, high blood pressure, or reduced mobility may qualify you. You'll need referral to NHS tier 3 weight management services or a clinical assessment via private prescribing.
What is the dose titration schedule for Mounjaro?
Mounjaro uses a gradual dose titration starting at 2.5 mg weekly for 4 weeks, then increasing every 4 weeks (5 mg, 7.5 mg, 10 mg, 12.5 mg) up to a maximum of 15 mg weekly. Your prescriber will adjust based on tolerability and response. Lower doses suit some patients well.
Can I take Mounjaro with fibromyalgia medications?
This depends on your specific fibromyalgia medications. Mounjaro may reduce absorption of some oral medications. Always inform your GP or prescriber of all fibromyalgia treatments (painkillers, muscle relaxants, antidepressants) before starting Mounjaro to check for interactions.
How long does it take to see weight loss results with Mounjaro?
Most people see gradual weight loss beginning around week 4–6 at higher doses. Clinical trials showed average losses of 15–21% body weight over 72 weeks. Results vary widely—some lose more, others less. Combine Mounjaro with reduced-calorie diet and physical activity (as tolerated with fibromyalgia) for best results.
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.