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
Blurred Vision on Mounjaro — What You Need to Know
Blurred vision is a reported side effect of Mounjaro (tirzepatide), the prescription-only GLP-1 and GIP receptor agonist used for weight management in the UK. If you're taking Mounjaro or considering it, understanding this potential side effect—including when it's temporary and when to contact your GP—is essential. This guide covers NHS guidance, what to expect, and how to manage blurred vision safely whilst using 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.
Blurred Vision as a Mounjaro Side Effect — NHS Context
Blurred vision is not listed as a very common side effect of Mounjaro in UK clinical summaries, but some users have reported visual changes after starting the medication. Why this happens: Rapid blood sugar changes—particularly if you have diabetes or prediabetes—can temporarily affect lens hydration and focusing ability in the eye. Additionally, Mounjaro may affect blood pressure and blood vessel function in the eye.
- Visual changes can occur at any dose but are more common during dose escalation phases
- Blurred vision may be temporary and resolve as your body adjusts
- Pre-existing eye conditions (diabetic retinopathy, glaucoma) may be more sensitive to medication effects
- Weight loss itself can sometimes trigger temporary vision changes
If you experience blurred vision whilst taking Mounjaro, contact your GP or prescriber promptly. Vision changes can occasionally signal more serious complications like retinopathy or acute angle-closure glaucoma, which require urgent assessment.
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 Urgent Medical Help
Seek immediate medical attention (call 111 or visit A&E) if you experience: Sudden severe blurred vision, vision loss in one or both eyes, eye pain with vision changes, flashing lights or new floaters, or a "shadow" or "curtain" across your vision. These may indicate retinal detachment, retinopathy complications, or acute glaucoma—all medical emergencies.
Contact your GP within 24–48 hours if blurred vision is mild, persistent, or gradually worsening. Your GP can refer you to an eye specialist (optometrist or ophthalmologist) for a thorough eye examination and determine whether Mounjaro is safe to continue or whether dose adjustment is needed. Keep your eye health team informed that you're taking tirzepatide.
- 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 blurred vision from Mounjaro be permanent?
Most cases of blurred vision linked to Mounjaro are temporary and resolve within days to weeks as your body adjusts or once dose stabilisation occurs. However, if vision changes persist beyond 2–3 weeks or worsen, they warrant urgent eye assessment. Permanent vision damage is rare but requires immediate professional evaluation to rule out serious complications.
Should I stop taking Mounjaro if my vision becomes blurred?
Do not stop Mounjaro without consulting your prescriber. Sudden cessation can cause other health problems. Instead, contact your GP or the prescriber who issued your Mounjaro KwikPen immediately. They can assess whether the blurred vision is medication-related, arrange an eye test, and advise whether to continue, adjust the dose, or switch treatments.
Is blurred vision more likely if I have diabetes?
Yes. People with type 2 diabetes or prediabetes taking Mounjaro may experience vision changes linked to rapid blood sugar improvements or fluctuations. Diabetic retinopathy (eye damage from diabetes) can also worsen or become apparent when blood sugar control improves quickly. If you have diabetes, inform your eye care team that you're starting Mounjaro so they can monitor you closely.
How does Mounjaro vs Wegovy differ regarding blurred vision risk?
Both Mounjaro (tirzepatide) and Wegovy (semaglutide) can cause vision changes, though the frequency is similar. Mounjaro is a dual GIP and GLP-1 agonist, whereas Wegovy is a GLP-1 agonist only—this may theoretically affect medication metabolism differently, but clinical evidence on vision side effects is limited for both. Your prescriber can discuss which is safer for your individual eye health.
Can I use our BMI calculator and GLP-1 weight loss calculator if I'm experiencing blurred vision on Mounjaro?
Yes. You can still use MyWeightCheck's free BMI calculator and GLP-1 weight loss calculator to monitor your progress, though you may want to increase text size if vision is blurred. These tools are helpful for tracking whether weight loss is occurring as expected, which can help you discuss progress with your GP or prescriber during your eye assessment appointment.
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.