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 Vision Changes — What UK Patients Need to Know
If you're taking Mounjaro (tirzepatide) and experiencing vision changes, it's important to understand what might be causing them and when to seek help from your GP. Vision changes are not listed as a common side effect of Mounjaro in UK clinical trials, but they can occur in people with type 2 diabetes or those at risk of diabetic complications. This guide explains what vision changes might mean, how they relate to Mounjaro eligibility and prescribing in the NHS, and what steps you should take if you notice any eye problems while on this medication.
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.
Vision Changes and Mounjaro — NHS Context
Vision changes during Mounjaro treatment can have several causes. Most commonly, they relate to changes in blood sugar levels rather than the medication itself. Rapid improvements in blood glucose control — which Mounjaro helps achieve — can temporarily affect how the eye lens focuses, causing blurred vision or difficulty adjusting between near and far objects. This typically resolves within weeks as your eyes adapt to your new blood sugar levels.
More serious vision changes — such as sudden blurriness, flashing lights, or dark spots — may indicate diabetic retinopathy complications, particularly if you have existing diabetes. This is why the MHRA requires that Mounjaro carries additional safety monitoring. When assessing eligibility for Mounjaro through NHS tier 3 specialist weight management services, your prescriber will review your diabetes history and any existing eye complications. If you have a history of diabetic retinopathy, your GP or prescriber must assess whether Mounjaro is appropriate for you before starting treatment. Report any vision changes immediately to your GP or eye care specialist.
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 Contact Your GP — NHS Guidance
Contact your GP immediately if you experience sudden vision loss, persistent blurriness, new floaters, flashing lights, or pain in or around your eyes while taking Mounjaro. These symptoms may indicate a serious eye condition requiring urgent assessment. The NHS advises that any new vision changes during weight loss treatment should be evaluated by your GP or optician, especially if you have diabetes or prediabetes.
When you access Mounjaro through NHS specialist services — typically tier 3 weight management clinics — your team will have access to your full medical history, including any existing eye conditions. This is one advantage of NHS prescribing: coordinated care between your GP, ophthalmologist (if you have one), and weight management specialist. If you're considering private prescribing of Mounjaro via online assessment, always disclose any vision problems or diabetes complications to the prescriber so they can make an informed decision about whether the medication is suitable for you.
- 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 directly cause vision changes?
Vision changes are not a common side effect of Mounjaro itself in clinical trials. However, they can occur due to rapid improvements in blood sugar control or, rarely, due to existing diabetic eye complications becoming apparent. The MHRA monitors Mounjaro closely (Black Triangle ▼ status), so report any vision changes to your GP promptly.
Are vision changes more likely with Mounjaro than with Wegovy?
Both Mounjaro (tirzepatide) and Wegovy (semaglutide) work on similar pathways and have similar safety profiles. Vision changes are not common with either. Individual factors like existing diabetes and blood sugar control are more relevant than the specific medication. Your prescriber can help determine which is more suitable for you.
Will vision changes stop if I stop taking Mounjaro?
Vision changes related to blood sugar improvements usually resolve within weeks as your eyes adjust to your new metabolic state. If caused by diabetic retinopathy, stopping Mounjaro may not reverse the changes — these require specialist eye care. Always discuss stopping Mounjaro with your prescriber, not your optician.
How does the NHS assess eye safety before prescribing Mounjaro?
NHS tier 3 specialist weight management services review your full medical history, including diabetes status and any known eye conditions. Your prescriber will consider your risk of diabetic complications. Use our free BMI calculator to check your current status, and be transparent with your GP about any vision concerns during your referral assessment.
Should I have my eyes checked before starting Mounjaro?
If you have diabetes or prediabetes, it's sensible to have a recent eye test before starting Mounjaro. Your GP or prescriber may recommend this. If accessing Mounjaro privately, disclose any eye conditions in your clinical assessment. The UK dose titration schedule (starting at 2.5 mg and escalating weekly over weeks) allows time to monitor for any emerging symptoms.
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.