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 and Appendicitis — Cost and Access in the UK
If you're considering Mounjaro (tirzepatide) for weight management, it's important to understand how this prescription-only injection may affect your digestive health, including appendicitis risk. This guide explains the potential connection between GLP-1 medications and gastrointestinal complications, the costs of accessing Mounjaro in the UK, and your options for getting treatment safely. Whether you're exploring NHS or private routes, understanding both the risks and access pathways will help you make an informed decision with your healthcare provider.
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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.
Private Mounjaro Costs by Dose in the UK
Private prescription costs for Mounjaro vary depending on the dose you're prescribed and your route of access. The following reflects typical private pricing for each KwikPen dose strength:
- 2.5 mg dose: Approximately £129–£159 per pen (4-week supply)
- 5 mg dose: Approximately £149–£179 per pen
- 7.5 mg dose: Approximately £169–£199 per pen
- 10 mg dose: Approximately £189–£229 per pen
- 15 mg dose (maximum): Approximately £229–£269 per pen
These are approximate costs and may vary by provider. Each KwikPen contains 4 once-weekly doses (one month's supply). Private prescriptions require an online clinical assessment with a UK-licensed prescriber, who will review your medical history, including any digestive conditions or appendicitis history, before issuing a prescription.
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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
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NHS vs Private Access Routes
NHS route: Mounjaro is available through NICE-approved specialist weight management services (tier 3), but availability and waiting times vary significantly by region. Your GP must refer you to a specialist service for assessment. Regional ICBs determine eligibility, and you may wait several months to over a year in some areas. The NHS path prioritises patients with significant obesity-related health conditions.
Private route: Online consultation with a UK-licensed prescriber is faster—typically within 24 hours. You'll complete a detailed health questionnaire covering digestive history, previous appendicitis, and current medications. If approved, your prescription is sent to a GPhC-registered pharmacy for dispensing. This route does not require NHS referral but requires you to cover the full cost of treatment, including consultations (usually £20–£50) and prescriptions.
- 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 Mounjaro increase appendicitis risk?
GLP-1 and GIP/GLP-1 medications like Mounjaro slow gastric emptying (how quickly food leaves the stomach). Theoretically, this could increase intestinal obstruction risk in susceptible individuals. However, clinical trial data does not show a significantly elevated appendicitis rate. Anyone with a history of appendicitis, severe gastroparesis, or recurring bowel obstruction should discuss Mounjaro safety with their GP or prescriber before starting treatment.
Can I get Mounjaro on the NHS if I've had appendicitis?
Having had appendicitis doesn't automatically disqualify you from NHS Mounjaro access, but it's a relevant medical history. You must declare this to your GP and the specialist weight management service. The prescriber will assess whether your past condition creates additional risk with Mounjaro dose titration. This assessment is part of the specialist evaluation process.
How much does a Mounjaro KwikPen cost privately?
A single KwikPen (4 doses, one month) costs approximately £129–£269 depending on dose strength—lower doses like 2.5 mg are cheaper, maximum 15 mg doses are more expensive. You'll also pay for the online consultation (£20–£50). Total first-month cost is typically £150–£320. Subsequent months cost the pen price plus any ongoing consultation fees.
What digestive side effects should I report immediately while on Mounjaro?
Seek urgent medical attention if you experience severe, persistent stomach pain radiating to your back (possible pancreatitis), sudden severe pain in the upper right abdomen (gallbladder), signs of bowel obstruction, or unexplained vomiting. These require same-day GP or A&E evaluation. Milder nausea, constipation, and diarrhoea are common but should improve as your body adjusts to the dose.
How is Mounjaro vs Wegovy assessed if I have digestive concerns?
Both Mounjaro (tirzepatide) and Wegovy (semaglutide) slow digestion, but Mounjaro's dual GIP/GLP-1 action may affect gastric emptying differently. Your prescriber will consider your individual digestive history when choosing between them. If you've had appendicitis or have ongoing digestive concerns, make this clear during your clinical assessment—the prescriber may recommend starting at a lower Mounjaro dose or exploring alternative weight management approaches first.
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