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 that works as a dual GIP and GLP-1 receptor agonist. While eye problems are not listed as common side effects, some people using GLP-1 medications report vision changes. If you're considering Mounjaro in the UK, it's important to understand potential eye-related risks, especially if you have diabetes or existing eye conditions. This guide explains what the evidence shows and what to watch for.
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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.
Mounjaro And Vision Changes — What The Evidence Shows
Vision changes reported by people using tirzepatide and other GLP-1 medications include temporary blurred vision, difficulty focusing, and changes in prescription strength. These are not listed as very common side effects in clinical trials, but some users report them during dose titration.
Important context: gradual weight management itself can cause temporary vision changes as the body adjusts. Mounjaro works by supporting gradual weight loss (typically 15–21% body weight over several months), which minimises sudden physical changes.
The most significant eye concern for people with type 2 diabetes or prediabetes is diabetic retinopathy — damage to blood vessels in the eye. GLP-1 medications including tirzepatide may improve blood sugar control, which can reduce long-term diabetic eye disease risk. However, rapid improvements in blood sugar control can temporarily worsen existing diabetic retinopathy in the short term. If you have diabetes and existing eye damage, your prescriber must assess this before starting Mounjaro.
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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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Accessing Mounjaro In The UK — Cost And Routes
Mounjaro is available in the UK through two routes: NHS specialist services or private prescription. NHS access requires referral to a tier 3 weight management service, and availability varies significantly by region with waiting lists often extending many months. Private access is through online consultations with UK-licensed prescribers, with costs typically ranging from £129–£320 per month depending on your dose.
Before any prescription, a licensed healthcare professional will assess your medical history, including any existing eye conditions or diabetes. This clinical assessment is essential — your prescriber needs to know about any vision problems, diabetic retinopathy, or recent eye procedures. Use our free BMI calculator to check your eligibility and our GLP-1 weight loss calculator to explore potential outcomes with professional support.
Before starting Mounjaro, inform your GP or prescriber if you have: diabetic retinopathy (current or history of), type 2 diabetes, any eye condition requiring treatment, or recent eye surgery. These factors don't necessarily exclude you from treatment but must be assessed individually. Regular eye tests with your optician are recommended, especially if you have diabetes. Discuss any vision changes with your prescriber immediately — they may adjust your dose or monitor you more closely.
- 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 permanent vision problems?
Permanent vision damage is not a listed side effect of Mounjaro in clinical trials. However, if you have existing diabetic retinopathy, rapid improvements in blood sugar control may temporarily worsen it. This requires monitoring by your healthcare team. Report any vision changes to your GP immediately.
What eye symptoms should I report to my prescriber?
Report blurred vision, difficulty focusing, flashing lights, floaters, shadows in your vision, or eye pain immediately. These could indicate retinopathy changes or other eye conditions requiring urgent assessment. Don't wait for your next appointment.
Is Mounjaro safe if I have type 2 diabetes?
Yes, Mounjaro can be prescribed to people with type 2 diabetes as it helps improve blood sugar control. However, your prescriber must know if you have diabetic retinopathy. GLP-1 medications may improve long-term eye health by controlling blood sugar, but rapid control changes require monitoring.
How often should I have eye tests while on Mounjaro?
If you have diabetes, the NHS recommends annual diabetic retinopathy screening. If you don't have diabetes but are using Mounjaro, routine eye tests as per your optician's recommendation are appropriate. Report any new vision changes between appointments.
Does the UK KwikPen injection affect my eyes?
The KwikPen device itself doesn't affect your eyes. Vision changes, if they occur, are related to Mounjaro's effect on blood sugar or gradual weight management, not the injection method. If vision changes happen, they're typically temporary during dose titration.
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