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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Coccyx Pain After Weight Loss: UK Prescription Options
Coccyx pain (tailbone discomfort) can sometimes occur during or after weight loss, particularly if weight loss is rapid or accompanied by reduced muscle support. In the UK, if you're managing your weight using prescription weight loss medication—such as Mounjaro, Wegovy, or other options available through NHS weight loss services or private prescribing—it's important to understand how these medicines work and what support is available. This guide explains UK-licensed weight management options and when to seek GP advice about any pain or discomfort during your weight loss journey.
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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.
UK Prescription Weight Loss Medications and Weight Management
If you're eligible for prescription weight loss treatment in the UK, several prescription medications are available to support your health goals. These include:
- Mounjaro (tirzepatide) — a dual GIP and GLP-1 receptor agonist that may help reduce appetite and support sustainable weight loss. Clinical trials showed users lost an average of 15–21% of body weight alongside diet and exercise.
- Wegovy (semaglutide) — a GLP-1 receptor agonist available as a once-weekly injection. Evidence suggests users may lose approximately 15% of body weight on average.
- Saxenda (liraglutide) — a daily GLP-1 injection option for eligible adults.
You're generally eligible if your BMI is 30 or above, or 27–29.9 with weight-related health conditions. All are prescription-only medicines requiring clinical assessment. Individual results vary significantly, and these medications work best alongside reduced-calorie diet and increased physical activity.
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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.
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NHS vs Private Access and Next Steps
In the UK, prescription weight loss medications are available through two main routes: NHS specialist weight management services (tier 3 services) and private online prescribing following clinical assessment. NHS access typically requires GP referral and varies by region. Private prescribing is available without NHS referral through GPhC-registered online pharmacies, though costs apply. If you experience coccyx pain or other discomfort during weight loss, speak with your GP or prescriber immediately—they can assess whether the pain is related to weight changes, posture, muscle loss, or other factors, and recommend appropriate support such as physiotherapy or postural advice.
- 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 prescription weight loss medication like Mounjaro cause coccyx pain?
Weight loss medications themselves don't typically cause coccyx pain. However, gradual weight management can sometimes affect muscle support around the tailbone area. If you develop pain while using weight loss medication, speak with your GP or prescriber. They can assess whether it's related to weight changes, posture, muscle loss, or an unrelated condition and recommend physiotherapy or other support if needed.
How can I find out if I'm eligible for prescription weight loss medication in the UK?
You're generally eligible if your BMI is 30 kg/m² or above, or 27–29.9 with at least one weight-related health condition such as type 2 diabetes, high blood pressure, or sleep apnoea. Speak with your GP about referral to NHS tier 3 weight management services, or use our free BMI calculator to check your starting point and understand your eligibility criteria.
What's the difference between NHS and private weight loss medication in the UK?
NHS access is through specialist tier 3 weight management services (requires GP referral, regional availability varies, and waiting lists can be long). Private access is through online prescribing services following clinical assessment, available without NHS referral, with costs typically ranging from £129–£320 per month depending on dose and provider.
Should I see my GP if I have pain during my weight loss journey?
Yes, absolutely. Any new pain or discomfort should be discussed with your GP or healthcare provider. They can determine whether it's related to weight loss, posture changes, reduced muscle support, or another condition entirely, and recommend appropriate treatment such as physiotherapy, postural adjustment, or other interventions tailored to your needs.
How much weight loss can I realistically expect with prescription medication?
In clinical trials, GLP-1 and dual GIP/GLP-1 medications resulted in average weight losses of 15–21% of body weight. However, individual results vary significantly based on dose, adherence, diet, exercise, and personal factors. Use our free GLP-1 weight loss calculator to see projected outcomes at different doses, and remember that medication works best alongside lifestyle changes, not instead of them.
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.