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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Best Probiotics to Take While Using Mounjaro
If you're taking Mounjaro (tirzepatide) and experiencing digestive side effects like nausea or changes in bowel habits, you may be wondering whether probiotics could help. The short answer is that there is no single "best" probiotic for Mounjaro users—what works depends on your individual circumstances, any existing health conditions, and what your GP recommends. This guide explains what probiotics are, how they interact with Mounjaro, and how to discuss probiotic use safely with your healthcare provider. Always consult your GP before starting any new supplement, especially while taking prescription weight loss medication.
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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.
Probiotics and Mounjaro: What You Need to Know
Probiotics are live beneficial bacteria designed to support gut health and digestion. They may help with symptoms like bloating, constipation, or diarrhoea—all common side effects when starting Mounjaro. However, the evidence for probiotics in managing Mounjaro-related digestive issues is limited.
Mounjaro works by slowing gastric emptying (how quickly food leaves your stomach) and affecting appetite signals. This can cause nausea, constipation, or diarrhoea, especially during dose titration. While probiotics may theoretically support digestive function, they are not a proven treatment for these side effects. More importantly, probiotics can interact with how your body absorbs other medications—including oral contraceptives, which Mounjaro also affects. This is why medical guidance before starting any probiotic supplement is essential. Your GP can advise whether a probiotic is suitable for you and help manage Mounjaro side effects through proven strategies like dietary adjustments and hydration.
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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.
Free Weight Loss Tools & Guides
Everything you need to understand your weight, explore medication options, and track your progress — completely free.
Discussing Supplements With Your GP: NHS Guidance
The NHS advises always informing your GP or prescriber about any supplements or probiotics you plan to take, especially while on prescription medications like Mounjaro. This is because supplements can affect how medications work and may cause unwanted interactions. When discussing probiotics with your healthcare provider, mention the specific probiotic strain (if you know it), when you plan to take it relative to your Mounjaro injection, and any existing digestive issues you're experiencing.
Your GP may suggest managing Mounjaro side effects through lifestyle changes first—such as eating smaller meals, staying hydrated, and increasing fibre gradually—before recommending supplements. If probiotics are suggested, your prescriber will help you choose an appropriate strain and discuss timing to minimise any potential interactions with your medication or oral contraceptives.
- 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 I take probiotics while on Mounjaro?
Possibly, but only with your GP's approval. Probiotics are not harmful in themselves, but they can affect how your body absorbs medications, including oral contraceptives. Always inform your prescriber before starting any probiotic supplement to ensure it's safe alongside your Mounjaro treatment.
Will probiotics help with Mounjaro side effects?
There is limited evidence that probiotics specifically treat Mounjaro-related digestive issues like nausea or constipation. Your GP may first recommend lifestyle approaches such as eating smaller meals, staying hydrated, and gradually increasing fibre. These often help more than supplements.
Which probiotic strain is best for Mounjaro users?
There is no evidence-based "best" strain for Mounjaro specifically. Different strains support different aspects of gut health. Your GP can recommend an appropriate strain based on your individual symptoms and health history, but this is a personalised decision.
Should I take probiotics at the same time as Mounjaro?
No. Mounjaro is injected once weekly, not taken orally, so there's no direct timing conflict. However, probiotics can affect how you absorb oral medications. If you take any oral contraceptives or other oral medications, space them out from probiotics as your GP advises.
What should I tell my GP before taking probiotics on Mounjaro?
Tell your GP about any digestive symptoms you're experiencing, any other medications or supplements you take (especially oral contraceptives), and ask whether probiotics would be appropriate for you. They can recommend a suitable option and explain any interaction risks specific to your situation.
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.