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
Free tracker included with every download this week
Does Mounjaro Affect Eyesight?
Mounjaro (tirzepatide) is a prescription-only weight management injection licensed in the UK. Some people have reported vision changes while using this medication, though these are not listed as common side effects. If you have existing eye problems or take Mounjaro for type 2 diabetes, it's important to understand how this injection may affect your eyesight and when to contact your GP. This guide explains what NHS guidance says about Mounjaro and vision concerns.
10,000+ calculations today · NHS-aligned thresholds · 100% free
Calculate Your BMI Instantly
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 Does NHS Guidance Say About Mounjaro and Eyesight?
The UK Medicines and Healthcare products Regulatory Agency (MHRA) has approved Mounjaro with a Black Triangle (▼) status, meaning it remains under additional monitoring. Eye problems are not listed as a common or very common side effect in the official product information, though vision changes have been reported by some users.
However, if you have type 2 diabetes or prediabetes, Mounjaro may indirectly affect your eyes through changes in blood sugar control. Diabetic retinopathy — damage to blood vessels in the retina — can worsen if blood sugar levels drop too quickly. If you're taking Mounjaro alongside diabetes medication, your GP or eye care specialist should monitor for any changes in your vision.
- Report any blurred vision, floaters, or visual changes to your GP immediately
- Have your eyes checked regularly if you have diabetes
- Inform your eye care professional that you're taking Mounjaro
- Do not stop your medication without consulting your prescriber
Clinically BackedWeight Loss
No appointments. No waiting rooms. Just care — from a UK-regulated online pharmacy.
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 Medical Advice About Mounjaro and Vision
Contact your GP or NHS 111 if you experience sudden vision changes, blurred eyesight, eye pain, or flashing lights while taking Mounjaro. These symptoms may indicate a serious eye condition, though they may not be directly caused by the medication.
If you have a history of diabetic retinopathy or other eye disease, your prescriber must know this before starting Mounjaro. In the UK, prescription weight loss medications like Mounjaro are dispensed following a clinical assessment where your full medical history is reviewed. Use our free BMI calculator to understand your baseline health status, and discuss any eye concerns with your GP before requesting a Mounjaro prescription through NHS specialist weight management services or private online prescribing.
- 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.
Can Mounjaro cause blurred vision as a side effect?
Blurred vision is not listed as a common side effect of Mounjaro by the MHRA, but some users have reported visual changes. If you experience blurred vision, contact your GP. In people with diabetes, rapid blood sugar changes can affect eyesight temporarily. Always inform your prescriber of any vision problems.
Is it safe to take Mounjaro if I have diabetic retinopathy?
If you have diabetic retinopathy, your GP or eye specialist must assess whether Mounjaro is safe for you. Rapid improvements in blood sugar control can sometimes worsen retinopathy temporarily. This requires careful monitoring and specialist guidance before starting the medication.
Does Mounjaro affect eyesight differently than Wegovy?
Both Mounjaro (tirzepatide) and Wegovy (semaglutide) are GLP-1-based medications, and neither lists vision changes as a common side effect. However, both may indirectly affect eyes in people with diabetes through blood sugar changes. Your prescriber will assess individual risk based on your medical history.
Should I have an eye test before starting Mounjaro?
If you have diabetes, prediabetes, or a history of eye disease, inform your GP before starting Mounjaro. They may recommend an eye test beforehand. An NHS clinical assessment before prescription will identify if an eye test is needed based on your personal health profile.
What should I tell my optician about taking Mounjaro?
Always inform your optician or eye care professional that you're taking Mounjaro, especially if you have diabetes. This helps them interpret any vision changes and monitor for diabetes-related eye complications. Regular eye checks are important for all people taking weight loss injections with diabetes.
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.