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 Dementia: What the Evidence Shows
There is currently no established link between Mounjaro (tirzepatide) and dementia risk in UK clinical evidence or approved guidance. Both Mounjaro and Wegovy are prescription-only weight loss medications licensed for UK adults with obesity or overweight with health conditions. This guide compares the two medications factually, explains their mechanisms, and clarifies what prescribers consider when assessing individual suitability. Always consult your GP for personalised advice about any weight loss medication.
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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 vs Wegovy: Mechanism and Trial Evidence
Mounjaro (tirzepatide) is a dual GIP and GLP-1 receptor agonist — it activates two natural hormone pathways to help regulate appetite and blood sugar control. In the SURMOUNT-1 clinical trial, participants achieved an average weight loss of approximately 15–21% of body weight over 72 weeks, depending on dose.
Wegovy (semaglutide) is a GLP-1 receptor agonist only — it activates a single hormone pathway. In the STEP-1 trial, participants achieved an average weight loss of approximately 15% of body weight over 68 weeks.
Both medications slow gastric emptying and may help reduce food cravings. Individual results vary significantly. Neither trial data nor UK regulatory approval documentation identifies dementia as a known risk. Your prescriber will assess which medication suits your health profile, taking into account your medical history, current medications, and any existing health conditions.
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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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Prescriber Assessment and Individual Suitability
Mounjaro requires a UK prescription and clinical assessment from a licensed prescriber — either through NHS specialist weight management services or private online prescribing. The same applies to Wegovy. A prescriber will review your full medical history, including any neurological concerns, before recommending either medication.
Both drugs are contraindicated in certain situations — for example, personal or family history of medullary thyroid carcinoma. If you have concerns about dementia risk, cognitive health, or any other health condition, discuss these openly with your GP or prescriber. They can weigh the benefits against risks for your specific circumstances and suggest alternatives if either medication is unsuitable.
- 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.
Is there evidence linking Mounjaro to dementia?
No. Current UK clinical trial data and regulatory guidance for Mounjaro do not identify dementia as a known risk. The SURMOUNT trials monitored participants over 72 weeks with no reported dementia-related concerns. If you have specific health worries, discuss them with your GP.
What is the difference between Mounjaro and Wegovy mechanism?
Mounjaro is a dual GIP and GLP-1 agonist (two hormone pathways), while Wegovy is a GLP-1 agonist only (single pathway). This dual action may contribute to Mounjaro's slightly higher average weight loss in trials, though individual results vary significantly.
Can I choose between Mounjaro and Wegovy on the NHS?
NHS prescription of either medication depends on specialist tier 3/4 weight management services in your region. Availability and choice vary. Private prescribing offers more choice but requires payment. Your prescriber will assess suitability based on your health profile.
What should I tell my prescriber before taking either medication?
Inform your prescriber of all medical conditions (especially neurological or mental health history), current medications (especially oral contraceptives or diabetes drugs), family history of thyroid cancer, and any concerns about cognitive health or dementia risk.
How do I check my current BMI to assess weight loss medication eligibility?
Use our free BMI calculator above to check your BMI instantly. You may be eligible for weight loss medication if your BMI is 30 or above, or 27 or above with weight-related health conditions. Always discuss eligibility with your GP or prescriber.
Ready to take control of your weight loss journey?
Start with a free BMI check, explore your GLP-1 options, or begin tracking your progress today. No sign-up. No cost. Just results.