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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Headaches and Mounjaro — What You Need to Know
Headaches are a common side effect reported during Mounjaro (tirzepatide) treatment in the UK. While most people experience mild symptoms that improve over time, understanding how headaches fit into the wider picture of Mounjaro side effects — and knowing how to access this prescription medication through either NHS or private routes — can help you make informed decisions about weight management. This guide covers managing headaches, accessing Mounjaro in the UK, and the costs involved.
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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.
Mounjaro Headaches: Frequency, Severity, and Management
Headaches are listed as a common side effect of Mounjaro, occurring in up to 1 in 10 people during clinical trials. Most headaches are mild to moderate and tend to reduce as your body adjusts to the medication over the first few weeks. Headaches may be linked to nausea, dehydration, or dietary changes as you adapt to reduced food intake.
- Prevention: Stay well hydrated, eat regular balanced meals (even in smaller portions), and avoid skipping meals entirely
- Management: Paracetamol or ibuprofen are typically safe to use; consult your GP if headaches are severe or persistent
- When to seek help: If headaches worsen significantly or are accompanied by vision changes, contact your GP immediately
Most people find headaches settle within 2–4 weeks as their body adjusts to the medication and dose escalation. If you're starting Mounjaro through NHS specialist services or a private online consultation, your prescriber will discuss all potential side effects upfront.
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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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Accessing Mounjaro in the UK: NHS vs Private Routes
In the UK, Mounjaro is available through two main routes: NHS specialist weight management services and private online prescribing. NHS access involves referral to a tier 3 or tier 4 weight management service and varies significantly by region; waiting lists can be lengthy. Private online prescribers can assess you without NHS referral, and treatment begins faster — typically within days. Costs range from approximately £129 to £320 per month depending on your dose. Both routes require a clinical assessment to confirm eligibility (BMI 30+ or 27+ with weight-related health conditions). Whichever route you choose, your prescriber will explain side effects, including headaches, and monitor your progress. Use our free GLP-1 weight loss calculator above to explore potential outcomes, and check your BMI with our calculator to confirm your eligibility.
- 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 headaches a serious side effect of Mounjaro in the UK?
Headaches are common but typically mild to moderate and tend to improve within 2–4 weeks as your body adjusts. They are not listed as a serious side effect. However, if headaches are severe, persistent, or accompanied by other symptoms like vision changes, contact your GP immediately for advice.
How much does Mounjaro cost on the NHS in the UK?
Mounjaro is available on the NHS through specialist tier 3 or tier 4 weight management services, but availability and waiting times vary significantly by region and Integrated Care Board (ICB). There is no direct cost to you if prescribed via the NHS, but access can involve lengthy waits.
What does Mounjaro cost on a private prescription in the UK?
Private Mounjaro costs typically range from £129 to £320 per month depending on your starting dose and the prescriber. Higher doses cost more. Prices vary between private providers. This is an estimate — confirm exact costs with your chosen provider.
Can I get Mounjaro on prescription without NHS referral in the UK?
Yes. Private UK-licensed prescribers can issue Mounjaro prescriptions following an online clinical assessment, without NHS referral. You'll be assessed for eligibility (BMI and health conditions), and if suitable, a prescription is issued to a GPhC-registered pharmacy for dispensing.
How do I access Mounjaro: NHS or private?
For NHS access, ask your GP for referral to a specialist weight management service (availability varies by region). For private access, find a UK online prescriber, complete an online health questionnaire, have a video consultation, and if approved, receive a prescription. Private typically takes days; NHS can take months to years depending on your region.
Ready to take control of your weight loss journey?
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