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 Problems — What You Need to Know
If you're considering Mounjaro (tirzepatide) for weight management or already taking it, you may have questions about potential eye-related side effects. Mounjaro is a prescription-only GLP-1 and GIP receptor agonist that's become increasingly available in the UK through NHS specialist services and private prescribing. While nausea and gastrointestinal side effects are most commonly reported, some users have reported vision changes. This guide explains what the evidence shows about Mounjaro and eye health, when to contact your GP, and how to monitor your vision safely while using this medication.
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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.
Vision Changes and Mounjaro — What the Evidence Shows
Vision changes have been reported by some people taking Mounjaro, though they are not listed as a common side effect in the official product information. The primary concern relates to diabetic retinopathy — a diabetes-related eye condition where high blood sugar damages blood vessels in the retina. Mounjaro rapidly improves blood sugar control, which is beneficial, but rapid improvements can occasionally cause temporary vision changes in people with existing diabetes or prediabetes.
This occurs because sudden blood sugar drops can affect the lens of the eye temporarily. The effect is usually temporary and improves as your eyes adjust. However, if you have existing diabetic retinopathy or are at high risk of diabetes-related eye complications, your GP or optometrist should monitor your vision more closely. The tirzepatide prescription dose you're prescribed will be assessed based on your individual health status, including any existing eye conditions. Always inform your prescriber if you have a history of eye problems or diabetes complications 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.
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Accessing Mounjaro in the UK — NHS vs Private Routes
Mounjaro is available in the UK through two main routes: NHS specialist weight management services and private prescription through online clinics. The KwikPen device comes in doses from 2.5 mg to 15 mg, with doses typically escalated every 4 weeks. NHS access is usually through tier 3 weight management services following a GP referral, though availability varies significantly by region and waiting times can be lengthy.
Private prescribing involves an online consultation with a UK-licensed prescriber who assesses your eligibility based on your BMI and health conditions. If approved, you'll receive a prescription dispensed by a GPhC-registered pharmacy. The Mounjaro UK prescription cost through private routes typically ranges from £129–£320 per month depending on the dose. Use our free BMI calculator to check your current status, and discuss all options with your GP before deciding between NHS and private access routes.
- 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 loss?
There is no evidence that Mounjaro causes permanent vision loss. Vision changes reported are typically temporary and related to rapid blood sugar improvements in people with diabetes. However, if you experience sudden vision changes, floaters, or flashing lights, contact your optometrist or GP immediately, as these can indicate serious eye conditions unrelated to Mounjaro.
Should I have an eye test before starting Mounjaro?
If you have diabetes, prediabetes, or a history of eye problems, inform your prescriber and optometrist before starting Mounjaro. A baseline eye examination can be helpful to establish your current eye health, especially if you have diabetic retinopathy risk. Your GP can advise whether a pre-treatment eye test is needed based on your individual circumstances.
What vision changes might happen when starting Mounjaro?
Some users report blurred vision, difficulty focusing, or temporary changes in vision clarity when blood sugar is improving rapidly. These typically resolve within days to weeks as your eyes adjust. If vision changes persist beyond a few weeks or worsen, contact your eye care professional or GP for assessment.
Is Mounjaro safe if I already have diabetic retinopathy?
Mounjaro may be prescribed to people with diabetic retinopathy, but requires careful monitoring. Rapid blood sugar improvement can temporarily worsen retinopathy symptoms in some people. Your GP and eye specialist should coordinate your care. Always disclose your retinopathy history before starting tirzepatide treatment.
How do I get a Mounjaro prescription in the UK if I'm concerned about my eyes?
Contact your GP to discuss your eye concerns and weight management options. They can refer you to a specialist weight management service (NHS) or you can pursue private prescribing through an online clinic. Any reputable prescriber will ask about your medical history, including eye conditions, before issuing a Mounjaro KwikPen prescription.
Ready to take control of your weight loss journey?
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