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 Eye Issues — What You Need to Know
Mounjaro (tirzepatide) is a prescription-only weight management injection available through NHS specialist services and private prescribers in the UK. Eye-related issues have been reported by some people taking Mounjaro, though they are not common. This guide explains what eye problems may occur, how they relate to weight loss medication, and when to contact your GP. If you're considering Mounjaro or currently taking it, understanding potential visual side effects helps you make informed decisions about your treatment.
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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.
Eye Issues Associated with Mounjaro — Clinical Evidence
Eye-related side effects reported with Mounjaro include blurred vision, changes in vision, and in rare cases, problems related to diabetic retinopathy (a complication of diabetes affecting the eyes). These are not listed as common side effects in clinical trials, but have been reported during real-world use. The mechanism is not fully understood, though gradual weight management and changes in blood sugar levels may play a role.
The SURMOUNT-1 clinical trial, which tested tirzepatide (the active ingredient in Mounjaro), recorded vision-related adverse events, though these were infrequent. People with type 2 diabetes who take Mounjaro may be at slightly higher risk of retinopathy changes — not because of the medication itself, but because gradual weight management and improved blood sugar control can sometimes unmask or temporarily worsen existing eye complications.
If you experience sudden vision changes, blurred vision, floaters, or flashing lights while taking Mounjaro, inform your GP immediately. Your optician or eye care professional should also know you are taking this medication.
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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.
What to Do If You Experience Eye Problems
Contact your GP urgently if you develop:
- Blurred or sudden vision changes
- Floaters or flashing lights
- Difficulty focusing
- Eye pain or redness
- Double vision
Your GP may refer you to an eye specialist for assessment. Before starting Mounjaro, inform your prescriber if you have a history of eye problems, diabetes-related eye disease, or recent eye surgery. If you've been prescribed Mounjaro through NHS tier 3 weight management services, you should have access to ongoing clinical monitoring, which includes screening for potential complications.
- 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 blurred vision a common side effect of Mounjaro?
Blurred vision is not listed as a common side effect of Mounjaro in clinical trials, though it has been reported in some patients using the medication. If you develop vision changes while taking Mounjaro, contact your GP or optician to rule out other causes and assess whether the medication may be responsible.
Can Mounjaro cause diabetic retinopathy?
Mounjaro does not directly cause diabetic retinopathy, but people with existing diabetes taking Mounjaro may experience changes in eye complications due to gradual weight management and blood sugar fluctuations. Regular eye checks are recommended if you have diabetes and are considering Mounjaro. Discuss your eye health history with your prescriber before starting treatment.
Should I have my eyes checked before starting Mounjaro?
If you have diabetes, a history of eye problems, or are over 40, an eye check before starting Mounjaro is advisable. Inform your optician that you are considering or taking tirzepatide. Your GP or prescriber can advise whether a baseline eye assessment is needed based on your individual health profile.
What's the difference between Mounjaro and Wegovy regarding eye issues?
Both Mounjaro (tirzepatide) and Wegovy (semaglutide) are GLP-1-based medications with similar profiles for rare eye-related side effects. Eye problems are uncommon with both but should be reported promptly. Your prescriber can advise which medication may be safer based on your specific health circumstances and eye health history.
How can I track any side effects while taking Mounjaro?
Keep a simple log of any symptoms you experience, including vision changes, and their timing relative to your Mounjaro dose. Our free progress tracker on this page can help you record not just weight, but also how you're feeling generally. Always report any new symptoms to your GP, especially vision-related changes, which warrant urgent review.
Ready to take control of your weight loss journey?
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