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 Blurred Vision — What UK Patients Need to Know
Blurred vision is a potential side effect of Mounjaro (tirzepatide), though it is not listed as a very common or common side effect. If you experience blurred vision or changes in your eyesight while taking Mounjaro, it's important to understand when this requires urgent medical attention and when to contact your GP. This guide explains what the NHS says about this side effect, how it relates to your health, and what steps to take if it occurs.
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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.
Why Mounjaro May Cause Blurred Vision
Blurred vision can occur with Mounjaro because tirzepatide affects blood sugar levels and how quickly food moves through your stomach. Changes in blood glucose can temporarily affect the lens of the eye, altering how light focuses on the retina. This is particularly relevant if you have type 2 diabetes or prediabetes — conditions that may have already affected your vision.
Additionally, gradual weight management itself can sometimes trigger temporary vision changes as your body adjusts. However, blurred vision is not a common side effect reported in clinical trials. Most people taking Mounjaro do not experience this symptom. If you do notice changes in your eyesight, the key is determining whether it requires urgent attention or routine GP follow-up.
Your prescriber will have assessed your individual health profile before issuing your tirzepatide prescription, including any existing eye conditions. Always inform your GP or prescriber if you have diabetic eye disease or other vision problems before starting Mounjaro.
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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.
When to Seek Urgent Medical Help
Contact NHS 111 or attend A&E immediately if you experience:
- Sudden, severe blurred vision or vision loss
- Eye pain or redness alongside vision changes
- Flashing lights, floaters, or dark spots appearing suddenly
- Double vision that develops suddenly
These symptoms may indicate diabetic retinopathy complications, detached retina, or other serious eye conditions that need urgent assessment. Do not delay — vision problems can progress rapidly and early treatment is critical.
For mild, gradual blurred vision without pain or other symptoms, contact your GP during normal hours. They can review your Mounjaro dose, check your blood sugar control, and refer you to an eye specialist if needed. Keep using MyWeightCheck's free GLP-1 weight loss calculator and BMI calculator to track your health progress alongside professional medical monitoring.
- 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?
No. Blurred vision is not listed as a very common or common side effect in clinical trials or the product information. However, it can occur due to changes in blood glucose levels or gradual weight management. If it develops, report it to your GP rather than stopping treatment without medical advice.
Should I stop taking Mounjaro if my vision becomes blurred?
Do not stop Mounjaro without speaking to your prescriber. If vision changes are mild and gradual, contact your GP to discuss. If vision loss is sudden or severe, seek urgent medical help via NHS 111 or A&E. Your prescriber may adjust your dose or investigate underlying causes.
Can Mounjaro worsen existing eye conditions like diabetic retinopathy?
If you have diabetic retinopathy, MHRA guidance suggests Mounjaro requires careful monitoring. Inform your prescriber of any existing eye conditions before starting treatment. Rapid blood sugar changes can affect retinopathy, so regular eye checks and GP monitoring are essential.
What should I tell my GP about blurred vision and Mounjaro?
Tell your GP when the blurred vision started, whether it's in one or both eyes, if it's constant or intermittent, and any other symptoms (pain, floaters, flashing lights). Also report your current Mounjaro dose and your recent blood sugar levels if you have diabetes. This helps your GP determine the cause.
How does MyWeightCheck help monitor my health while taking Mounjaro?
Use our free BMI calculator to track your weight progress and understand your health category. Our GLP-1 weight loss calculator can show projected outcomes at different doses. Keep records of any side effects using our progress tracker to share with your GP at appointments.
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.