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 Flu Symptoms: UK Cost and Access Information
Mounjaro (tirzepatide) can cause flu-like symptoms in some people, particularly during the initial weeks of treatment or when increasing doses. Understanding what these symptoms are, how long they typically last, and how to access Mounjaro in the UK—whether through the NHS or privately—can help you make informed decisions about prescription weight management. This guide covers everything you need to know about Mounjaro flu symptoms alongside practical information about costs and eligibility in the UK.
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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.
What Are Mounjaro Flu-Like Symptoms and When Do They Occur?
Flu-like symptoms with Mounjaro can include fatigue, headache, dizziness, and general malaise, though these are not actually caused by a virus. These symptoms may occur during the initial adjustment phase (weeks 1–4) or when dose titration increases the concentration of tirzepatide in your body. Most people experience these effects as mild and temporary, typically resolving within a few days as the body adjusts to the medication.
- Fatigue and tiredness are among the most commonly reported symptoms
- Headaches may accompany nausea or gastrointestinal changes
- Dizziness can occur, especially if you stand up quickly
- Symptoms usually improve within 3–7 days of starting or increasing your dose
If symptoms persist beyond two weeks or become severe, contact your GP or the prescriber who issued your prescription. In rare cases, severe fatigue may indicate a need for dose adjustment. Use our free GLP-1 weight loss calculator to understand what dose escalation might look like over your treatment timeline.
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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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Mounjaro Cost and Access in the UK: NHS vs Private Routes
In the UK, you can access Mounjaro through two main routes: the NHS or private prescription. NHS access is through specialist tier 3 weight management services, typically via GP referral, though availability and waiting times vary significantly by region and ICB (Integrated Care Board). Private access is available through GPhC-registered online prescribers without NHS referral, costing approximately £129–£280 per month depending on dose.
- NHS: Free on prescription, but long waiting lists in many areas; requires specialist service referral
- Private: Faster access, ranges from initial consultation to first dose in 1–2 weeks; cost varies by dose and provider
- Online consultations: Prescriber assesses your BMI, health history, and eligibility before issuing a prescription
Calculate your BMI using our free BMI calculator to check your eligibility (BMI 30+ or 27+ with weight-related health conditions) before booking a consultation.
- 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.
Are flu-like symptoms with Mounjaro dangerous?
Flu-like symptoms from Mounjaro are typically mild and temporary, not dangerous. They usually resolve within 3–7 days as your body adjusts. However, if symptoms persist beyond two weeks, worsen, or you develop severe fatigue, contact your GP or prescriber immediately. Severe or persistent symptoms may warrant a dose adjustment.
How much does Mounjaro cost privately in the UK?
Private Mounjaro costs range from approximately £129–£280 per month depending on the dose (2.5 mg to 15 mg). Initial consultation fees vary but typically range from £30–£50. NHS prescription is free, but access via the NHS involves waiting lists that can span months to years depending on your region and local specialist service availability.
Can I get Mounjaro through the NHS in the UK?
Yes, Mounjaro (tirzepatide) is NICE-approved for NHS use through specialist tier 3 weight management services. Access requires a GP referral and assessment, but availability varies significantly by ICB. Some regions have long waiting lists. Private access may be faster if you wish to start treatment sooner without waiting.
What is the difference between Mounjaro and Wegovy for cost and access?
Mounjaro (tirzepatide) and Wegovy (semaglutide) are both available privately and via NHS, with similar private costs (£129–£280/month). Mounjaro is a dual GIP+GLP-1 agonist with a maximum dose of 15 mg weekly. Wegovy is a GLP-1 agonist with a maximum dose of 2.4 mg weekly. Clinical trials showed Mounjaro achieved slightly higher average weight loss, but individual results vary significantly.
What happens if I experience flu-like symptoms during Mounjaro dose titration?
Flu-like symptoms during dose increases are common and usually mild. Continue your regular schedule unless symptoms are severe. Stay hydrated, rest, and eat small, regular meals. If symptoms persist beyond one week or interfere with daily life, contact your prescriber—they may adjust your dose schedule or recommend additional support during this adjustment period.
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