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
Mounjaro and Retinopathy: What UK Patients Need to Know
Retinopathy is damage to the blood vessels in the retina, often linked to type 2 diabetes or rapid blood sugar changes. If you're considering Mounjaro (tirzepatide) for weight management, understanding how it may affect eye health is important. This guide explains the relationship between GLP-1 and GIP receptor agonists like Mounjaro, blood sugar control, and retinopathy risk. We'll cover what the evidence shows, when to seek eye screening, and how to discuss this with your GP before starting treatment.
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.
Retinopathy Risk and GLP-1 Medications: What the Evidence Shows
Retinopathy occurs when high blood sugar levels damage small blood vessels in the retina over time. The relationship between weight loss medications and retinopathy is complex. Mounjaro (tirzepatide) works as a dual GIP and GLP-1 receptor agonist, helping improve blood sugar control in people with type 2 diabetes or prediabetes.
Clinical trials and real-world data suggest that improved blood sugar control with Mounjaro generally reduces retinopathy risk long-term. However, rapid improvements in blood sugar levels (sometimes called "rapid glycaemic control") can occasionally cause transient worsening of existing retinopathy in the short term, particularly in people with pre-existing diabetic retinopathy. This is not unique to Mounjaro — it can occur with any treatment that rapidly improves blood sugar control, including insulin.
If you have existing diabetic retinopathy, your GP or eye specialist should assess whether Mounjaro is suitable before starting treatment. Baseline eye screening is recommended before beginning any weight loss medication if you have type 2 diabetes or prediabetes.
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.
Eye Screening and Monitoring on Mounjaro: UK Guidance
The NHS recommends that adults with type 2 diabetes should have regular diabetic retinopathy screening (typically annually through the NHS Diabetic Eye Screening Programme). If you're starting Mounjaro, discuss eye health with your GP before treatment begins.
During Mounjaro treatment, continue regular eye screening appointments as recommended. If you experience sudden changes in vision, flashing lights, floaters, or blurred sight — seek urgent medical attention from your GP or eye casualty. These symptoms may indicate retinopathy progression or other eye complications unrelated to Mounjaro.
Weight loss and improved blood sugar control with Mounjaro can benefit overall metabolic health and reduce long-term diabetes complications, but individual eye health assessment is essential before starting treatment.
- 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 retinopathy?
Mounjaro itself does not directly cause retinopathy. However, rapid improvements in blood sugar control can occasionally cause transient worsening of pre-existing retinopathy. This is a known effect of any rapid blood sugar improvement, not unique to Mounjaro. Long-term improved control reduces retinopathy risk.
Should I have an eye test before starting Mounjaro?
Yes. If you have type 2 diabetes or prediabetes, baseline eye screening is recommended before starting Mounjaro. This establishes your baseline status and allows your GP or eye specialist to advise whether treatment is suitable for you.
What's the difference between Mounjaro and Wegovy for eye health?
Both Mounjaro (tirzepatide) and Wegovy (semaglutide) are GLP-1 receptor agonists that improve blood sugar control. Mounjaro is a dual GIP and GLP-1 agonist. Eye health risks and benefits are similar — rapid blood sugar improvement can transiently worsen pre-existing retinopathy, but long-term control reduces risk.
How often should I have eye screening while taking Mounjaro?
Continue regular NHS Diabetic Eye Screening Programme appointments as recommended (typically annually). Your GP or eye specialist may recommend more frequent screening if you have existing retinopathy. Always discuss monitoring frequency with your healthcare team.
What should I do if my vision changes on Mounjaro?
Seek urgent medical attention. Contact your GP, eye casualty, or call 111 if you experience sudden vision changes, flashing lights, floaters, or blurred sight. These symptoms need prompt assessment to rule out serious eye complications.
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.