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, Epilepsy, and Weight Management — What You Need to Know
If you have epilepsy and are considering weight management medication, it's important to understand how Mounjaro (tirzepatide) interacts with your specific health situation. This guide explains the key safety considerations, how Mounjaro works compared to alternatives like Wegovy, and why a thorough prescriber assessment is essential before starting any weight loss injection. Epilepsy and weight management can both significantly affect your health, so personalised medical guidance is vital.
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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.
How Mounjaro and Wegovy Differ in Mechanism and Clinical Context
Mounjaro (tirzepatide) is a dual GIP and GLP-1 receptor agonist — meaning it activates two different hormone pathways in the body. In clinical trials (SURMOUNT-1), participants on Mounjaro lost an average of 15–21% of their body weight at various doses, alongside reduced-calorie diet and increased physical activity.
Wegovy (semaglutide) is a single GLP-1 receptor agonist, activating only the GLP-1 pathway. STEP trial data showed average weight loss of approximately 15% body weight on the maximum 2.4 mg dose.
Both are prescription-only injections given once weekly. The key difference is mechanism: Mounjaro's dual action may provide additional appetite regulation, but both work on overlapping pathways. Neither medication is specifically contraindicated in epilepsy, but individual suitability depends on your specific epilepsy type, current anticonvulsant medications, and overall health profile — this is why prescriber assessment is crucial.
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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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Why Epilepsy Requires Specialist Prescriber Assessment
Epilepsy is a complex neurological condition managed with specific anticonvulsant medications (such as levetiracetam, lamotrigine, or sodium valproate). When considering weight management injections like Mounjaro or Wegovy, your prescriber needs to assess:
- Whether the injection might affect seizure threshold or medication absorption
- Your seizure control stability on current medication
- Any potential drug interactions between your anticonvulsants and the weight loss injection
- Your overall metabolic and neurological health
This is not a decision to make without qualified medical input. Your GP can refer you to specialist weight management services (available through NHS tier 3 services or private prescribers) where a prescriber can assess your full health picture and advise on suitability. Our free BMI calculator can help you understand your baseline health metrics before that conversation.
- 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 I take Mounjaro if I have epilepsy?
Mounjaro is not absolutely contraindicated in epilepsy, but suitability depends on your specific seizure type, anticonvulsant medications, and seizure control. A qualified prescriber must assess your individual situation before any prescription. Never start without this assessment — your GP or a licensed prescriber can discuss whether Mounjaro is appropriate for you.
Does Mounjaro interact with epilepsy medications?
Mounjaro itself is not known to directly interact with most anticonvulsants, but prescriber assessment is essential because weight loss medications can affect stomach function and oral medication absorption. Your prescriber needs to know all your current medications to ensure safe combined use.
Is Wegovy safer than Mounjaro for epilepsy?
Both are prescription-only and require individual assessment in epilepsy. Neither is inherently "safer" — suitability depends on your seizure type, anticonvulsants, and overall health. Your prescriber will advise which (if either) is appropriate after reviewing your full medical history.
How do I access weight management medication if I have epilepsy?
Contact your GP and mention both your epilepsy and interest in weight management. Your GP can refer you to NHS tier 3 specialist weight management services or you can pursue private prescribing through a licensed UK prescriber who can conduct a thorough clinical assessment of your epilepsy and suitability.
What's the difference between Mounjaro's dual mechanism and Wegovy's single mechanism?
Mounjaro (tirzepatide) is a GIP and GLP-1 agonist — dual action. Wegovy (semaglutide) activates GLP-1 only. Mounjaro's dual mechanism may provide additional appetite suppression, but clinical trial data shows both effective for weight loss. In epilepsy, mechanism differences matter less than individual prescriber assessment of your specific needs.
Ready to take control of your weight loss journey?
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