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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Does Mounjaro Cause Headaches?
Yes, headaches are a recognised side effect of Mounjaro (tirzepatide), though they are relatively uncommon compared to other side effects. In clinical trials, fatigue and dizziness were more frequently reported than headaches. If you experience persistent headaches after starting Mounjaro, it's important to discuss this with your prescriber, as they can advise whether the symptom is likely to settle or suggest management strategies. This guide explains what the evidence shows about Mounjaro headaches, when they typically occur, and what to do if you experience them.
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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 — What the Evidence Shows
Headaches are listed as a common side effect of Mounjaro in the UK product information, meaning they may affect up to 1 in 10 people taking the medication. However, in the SURMOUNT clinical trials, the actual reported rate was lower than some other side effects like nausea, diarrhoea, and vomiting.
When headaches do occur with Mounjaro, they typically develop in the first few weeks of treatment or during dose titration (when your dose is being gradually increased). Many people find that headaches improve or resolve as their body adjusts to the medication, usually within 2–4 weeks. If you're taking Mounjaro alongside a reduced-calorie diet, dehydration can contribute to headaches, so staying well hydrated is important.
Headaches may also be related to other Mounjaro effects — for example, if nausea or dizziness is present, these can trigger or worsen headaches. Your prescriber can help determine whether the headache is directly related to the tirzepatide or connected to other factors.
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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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Managing Headaches and Accessing Mounjaro in the UK
If you develop headaches while taking Mounjaro, contact your prescriber before taking over-the-counter pain relief to rule out any other causes. Your GP or the prescriber managing your prescription can advise whether paracetamol or ibuprofen is appropriate for you. Headaches may settle without intervention, but they should not be ignored if they're severe or persistent.
In the UK, Mounjaro is available through two routes: NHS specialist weight management services (tier 3 services) and private online prescribing following a clinical assessment. Whichever route you use, your prescriber will monitor your side effects and can adjust your dose or discuss management strategies if headaches are problematic. Use our free GLP-1 weight loss calculator to understand what Mounjaro doses are available and their typical outcomes, and our BMI calculator to check whether you may be eligible for prescription weight loss treatment.
- 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 Mounjaro headaches permanent?
No. Most headaches associated with Mounjaro resolve within 2–4 weeks as your body adjusts. However, if headaches persist beyond 4 weeks or worsen, discuss this with your prescriber — they may suggest a dose adjustment or investigate other causes.
Should I stop Mounjaro if I get a headache?
Do not stop Mounjaro without speaking to your prescriber first. A single headache is unlikely to require stopping the medication. However, if headaches are severe, frequent, or accompanied by other concerning symptoms (vision changes, severe dizziness), contact your prescriber urgently for advice.
How does Mounjaro compare to Wegovy for headaches?
Both Mounjaro and Wegovy can cause headaches as a common side effect. There is no clear evidence that one causes headaches more frequently than the other. Individual responses vary, and your prescriber can discuss which medication may be more suitable for you based on your health history.
Can I take paracetamol with Mounjaro?
Paracetamol is generally considered safe to use alongside Mounjaro for headache relief, but always check with your prescriber first, especially if you're taking other medications. Your prescriber can confirm what's appropriate for you.
What's the difference between Mounjaro side effects and other health conditions?
Headaches can have many causes — stress, dehydration, hormonal changes, or other health conditions. Your prescriber will help determine whether your headache is likely related to Mounjaro or another cause. Keep a record of when headaches occur to share with them.
Ready to take control of your weight loss journey?
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