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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Blurred Vision and Mounjaro — What You Need to Know
Blurred vision is a reported side effect that some people experience while taking Mounjaro (tirzepatide) in the UK. While it's not one of the most common side effects, it's important to understand what may cause it, when it typically occurs, and what steps you can take if you experience vision changes. If you're considering Mounjaro or already taking it, this guide explains the connection and advises when to seek medical help. Always contact your GP if you have concerns about any symptoms.
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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.
What Causes Blurred Vision with Mounjaro?
Blurred vision with Mounjaro may occur through several mechanisms. First, gradual weight management can cause changes in blood sugar levels, which affects the lens of the eye and temporarily impacts focus. Second, if you have type 2 diabetes or prediabetes, improved blood sugar control with Mounjaro can cause a refractive shift — meaning your eyes adjust to new glucose levels, leading to temporary blurred vision. Third, dehydration is a possible contributing factor, as Mounjaro side effects like nausea and diarrhoea can reduce fluid intake. Finally, some people experience blurred vision as part of the initial adjustment period when starting tirzepatide or escalating doses during dose titration. In clinical trials, vision changes were reported in a small proportion of users. If you experience persistent blurred vision, contact your GP to rule out other causes and discuss whether continuing Mounjaro is appropriate for your situation.
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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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Managing Blurred Vision and When to Seek Help
If you develop blurred vision while taking Mounjaro, first ensure you're staying well hydrated and eating balanced meals — dehydration and gradual weight management can worsen the symptom. Many people find vision improves as their body adjusts to the medication, typically within days or weeks. However, seek urgent medical attention if blurred vision is severe, sudden, or accompanied by eye pain, flashing lights, or loss of peripheral vision — these could indicate a serious eye condition like retinopathy or acute angle-closure glaucoma. Contact your GP promptly if blurred vision persists beyond two weeks or worsens. Your GP can assess whether the symptom is related to Mounjaro, your diabetes control, or another underlying cause. Be transparent with your prescriber about all side effects so they can decide whether to continue, pause, or adjust your Mounjaro dose.
- 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 very common side effect of Mounjaro in UK prescribing information, but it is reported by some users. Vision changes are more common in people with diabetes when blood sugar control improves rapidly. If you experience it, contact your GP to discuss whether it's related to Mounjaro or another cause.
Can Mounjaro cause permanent vision damage?
No evidence suggests Mounjaro causes permanent vision damage. However, in people with existing diabetic retinopathy, rapid improvements in blood sugar control can temporarily worsen vision. Your GP can monitor this if you have diabetes. Always report vision changes to your healthcare provider promptly.
How long does blurred vision last when taking Mounjaro?
For most people, blurred vision resolves within days to weeks as the body adjusts to the medication and blood sugar levels stabilise. However, duration varies between individuals. If blurred vision persists beyond two weeks, contact your GP to investigate other possible causes and discuss whether to continue Mounjaro.
What's the difference between Mounjaro and Wegovy for vision side effects?
Both Mounjaro (tirzepatide) and Wegovy (semaglutide) are GLP-1-based medications that can affect vision through similar mechanisms — improved blood sugar control and gradual weight management. Neither has a significantly higher risk. Vision side effects depend more on individual factors like diabetes status and rate of weight loss than on which medication is used.
Should I stop taking Mounjaro if my vision becomes blurred?
Do not stop Mounjaro without speaking to your prescriber first. Contact your GP or the clinician who prescribed it to discuss your symptoms. They will assess whether blurred vision is medication-related and advise whether to continue, pause, or adjust your dose. In rare cases of severe vision changes, seek urgent care immediately.
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