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 Vision Changes — What You Need to Know
Vision changes, including rare cases of serious vision problems, are a recognised potential side effect of Mounjaro (tirzepatide) in the UK. This guide explains what you should know about Mounjaro and eye health, when to seek medical attention, and how to access this prescription medication safely through NHS or private routes. If you're considering Mounjaro or already using it, understanding vision-related risks is essential for informed decision-making alongside your GP or prescriber.
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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.
Vision Changes and Mounjaro — What the Evidence Shows
Mounjaro (tirzepatide), a dual GIP and GLP-1 receptor agonist prescription injection, can in rare cases affect vision. Changes reported include blurred vision, flashing lights, and in serious cases, complications related to diabetic retinopathy—particularly in people with existing type 2 diabetes. The mechanism isn't fully understood, but gradual weight management and changes in blood sugar control may play a role.
- Most vision changes are mild and temporary, resolving as the body adjusts
- Serious vision problems (diabetic retinopathy worsening) are rare but require urgent medical attention
- People with pre-existing diabetes or diabetic eye disease face higher risk
- Regular eye monitoring is recommended, especially during the first weeks of treatment
Your prescriber should assess your individual risk before starting Mounjaro. Inform them immediately of any vision changes: sudden blurred vision, floaters, flashing lights, or dark spots in your visual field.
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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
Everything you need to understand your weight, explore medication options, and track your progress — completely free.
UK Access Routes — NHS vs Private Prescription
In the UK, Mounjaro is prescription-only and available through two routes. NHS access is through specialist tier 3 weight management services following GP referral; availability and waiting times vary significantly by region. Private access is through GPhC-registered online pharmacies offering consultations with UK-licensed prescribers, without NHS referral.
Both routes require a clinical assessment to confirm eligibility and review your medical history, including any existing eye conditions or diabetes. Private prescription typically costs £129–£320 per month depending on dose and provider. Our GLP-1 weight loss calculator can help you understand potential outcomes at different doses, whilst our BMI calculator provides baseline health context before consultation.
When accessing Mounjaro privately, you'll typically complete an online health questionnaire reviewed by a UK-licensed prescriber. Your medical history, current medications, and any vision-related concerns are assessed. If approved, a prescription is issued to a GPhC-registered pharmacy for dispatch. The Mounjaro kwikpen (pre-filled injection device) is injected once weekly at home. Regular communication with your prescriber about side effects—including any vision changes—is essential throughout 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.
What vision problems can Mounjaro cause?
Mounjaro can cause blurred vision, flashing lights, or floaters in rare cases. More seriously, it may worsen diabetic retinopathy in people with existing type 2 diabetes. Most cases are mild and temporary, but any sudden vision changes require immediate medical attention from your GP or eye doctor.
Who is at higher risk of vision changes from Mounjaro?
People with type 2 diabetes, pre-existing diabetic eye disease, or uncontrolled blood sugar are at higher risk. gradual weight management itself can temporarily affect vision. Your prescriber will assess your individual risk during consultation before prescribing Mounjaro.
How much does Mounjaro cost on prescription in the UK?
Private Mounjaro prescriptions typically cost £129–£320 per month depending on dose and provider. NHS access is free but available only through specialist tier 3 weight management services with regional availability. Costs vary by dose: lower doses (2.5–5 mg) cost less than higher maintenance doses (10–15 mg).
Can I get Mounjaro on the NHS for weight loss?
Yes, Mounjaro is NICE-approved for NHS use in specialist weight management services. Access requires GP referral to your local tier 3 service. Eligibility depends on BMI (30+ or 27+ with health conditions) and varies by region; waiting lists can be lengthy in many areas.
How do I access Mounjaro privately in the UK?
Use an online consultation with a GPhC-registered pharmacy offering Mounjaro prescriptions. Complete a health questionnaire, have it reviewed by a UK-licensed prescriber, and if approved, receive a prescription dispensed by post. The process typically takes 3–7 days from consultation to delivery.
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.