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 Thrush: What's the Link?
Mounjaro (tirzepatide) is a prescription-only weight management injection that may affect your body's ability to regulate blood sugar and immune function. Some people taking GLP-1 and dual GIP/GLP-1 medications report yeast infections or thrush as a side effect. This guide explains the link between Mounjaro and thrush, when it might occur, and what steps you can take if you develop symptoms. Always discuss any new symptoms with your GP or the prescriber who issued your tirzepatide prescription.
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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.
How Mounjaro May Contribute to Thrush
Thrush (oral or vaginal yeast infection) occurs when the fungus Candida albicans grows excessively in warm, moist environments. While thrush itself is not listed as a common side effect in Mounjaro clinical trials, several mechanisms may increase your risk:
- Blood sugar changes: Mounjaro improves blood sugar control, but fluctuations during dose escalation or if you miss a dose may affect immune function and create an environment where yeast thrives
- Reduced saliva flow: Some people experience dry mouth on Mounjaro, and reduced saliva means less natural antimicrobial protection in the mouth
- Altered gut bacteria: Weight loss medications may shift your gut microbiome, affecting the balance of protective bacteria that normally prevent yeast overgrowth
- Immune system adaptation: Your immune system adjusts as your body changes during weight loss, potentially reducing defences against Candida temporarily
If you develop thrush symptoms whilst taking Mounjaro, your GP can confirm the diagnosis and prescribe antifungal treatment—thrush is easily treatable.
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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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Thrush Symptoms and When to Contact Your GP
Oral thrush signs: white patches on the tongue or inside the cheeks, difficulty swallowing, loss of taste, or mouth pain.
Vaginal thrush signs: itching, burning during urination, thick white discharge, or soreness.
Contact your GP if symptoms persist for more than a few days, worsen despite home care, occur frequently, or cause significant discomfort. Your GP can prescribe antifungal tablets (such as fluconazole) or suggest topical treatments. Inform your prescriber that you're taking Mounjaro, as some antifungal medications may interact with other drugs you're taking. Keep a note of when thrush occurs relative to your Mounjaro dose changes—this pattern information helps your GP assess whether the medication is likely responsible.
- 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.
Is thrush a common side effect of Mounjaro?
Thrush is not listed as a "common" side effect in Mounjaro clinical trials. However, some people report it anecdotally. GLP-1 and GIP/GLP-1 medications can indirectly increase thrush risk through blood sugar changes, dry mouth, and immune system shifts—not through a direct pharmacological effect.
Can I prevent thrush while taking Mounjaro?
Yes. Maintain good oral hygiene, stay well hydrated, avoid sugary foods and drinks, wear breathable underwear, and manage stress. If you have a history of thrush, discuss preventive measures with your GP. These steps support your immune system during weight loss.
Will I need to stop Mounjaro if I develop thrush?
No. Thrush is treatable with antifungal medication and does not usually require stopping Mounjaro. Your GP and prescriber will work together to manage both conditions. If thrush is severe or recurrent, your prescriber may adjust your Mounjaro dose or consider alternatives.
How long does it take to treat thrush?
Oral thrush typically improves within 7–14 days of antifungal treatment. Vaginal thrush usually clears within 3–7 days. However, if symptoms persist beyond these timeframes, return to your GP for reassessment—recurrent thrush may indicate an underlying issue.
Should I mention thrush to my Mounjaro prescriber?
Yes. Always inform your prescriber of any new symptoms, including thrush. They need to know the full picture of how Mounjaro affects you, especially if thrush occurs repeatedly or at specific points in your dose titration schedule.
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