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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How Long Do Sulphur Burps Last on Mounjaro?
Sulphur burps (also called rotten egg burps) are a known side effect that some people experience when taking Mounjaro (tirzepatide). These typically last between a few days to 2–3 weeks, though duration varies between individuals. They tend to be more common when starting the medication or increasing your dose, and usually improve as your body adjusts. If you're considering Mounjaro or currently taking it, understanding what to expect can help you manage this side effect confidently.
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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.
Why Sulphur Burps Happen with Mounjaro
Sulphur burps occur because Mounjaro slows how quickly food moves through your stomach (a process called gastric emptying). When food stays in your stomach longer, bacteria break it down more slowly, producing hydrogen sulphide gas — which creates that distinctive rotten egg smell. This is not dangerous, but it can be uncomfortable and socially awkward.
Why timing matters: Sulphur burps are most common in the first 2–4 weeks after starting Mounjaro or when increasing your dose. As your digestive system adapts to the medication, this side effect typically reduces significantly. Most people find it improves considerably by weeks 3–4 on each new dose.
Dose and duration: There's no direct link between Mounjaro dose (2.5 mg to 15 mg) and sulphur burp severity — some people experience it at lower doses, others at higher doses. Individual variation is significant.
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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.
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Everything you need to understand your weight, explore medication options, and track your progress — completely free.
Managing Sulphur Burps While Taking Mounjaro
Dietary strategies: Eat smaller, more frequent meals rather than large ones. Choose easily digestible foods like lean protein, vegetables, and whole grains. Avoid fatty, greasy, or heavily processed foods that stay in the stomach longer. Ginger tea, peppermint, or fennel may help settle digestion.
Lifestyle adjustments: Stay hydrated and move gently after eating (a short walk can help digestion). Chew food thoroughly. Take Mounjaro as directed — never skip doses or stop without consulting your GP, as this won't prevent the side effect and may affect your treatment plan.
When to seek help: If sulphur burps persist beyond 4 weeks on a stable dose or become severe, contact your prescriber. They may suggest a temporary dietary adjustment or, rarely, dose timing changes.
- 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.
Are sulphur burps a sign that Mounjaro isn't working for me?
No. Sulphur burps are a temporary side effect related to how Mounjaro slows gastric emptying, not how well the medication is working for weight management. They're unrelated to whether tirzepatide is effectively reducing appetite or supporting weight loss. Most people find they improve within 2–4 weeks as the body adapts.
How is Mounjaro different from Wegovy when it comes to sulphur burps?
Both Mounjaro (tirzepatide — a dual GIP/GLP-1 agonist) and Wegovy (semaglutide — a GLP-1 agonist only) can cause sulphur burps because both slow gastric emptying. Clinical experience suggests sulphur burps may be slightly more common with Mounjaro due to its dual mechanism, but individual experience varies. Direct comparison isn't straightforward.
Can I take anything to stop sulphur burps immediately?
There's no medication that immediately stops them, but you can manage them: eat smaller meals, stay hydrated, avoid fatty foods, and try ginger or peppermint tea. Over-the-counter simethicone (Infacol) may help some people by reducing gas. If they're severe or persistent beyond 4 weeks, your prescriber can advise on further options.
Do sulphur burps mean I should stop taking Mounjaro?
No — sulphur burps are a temporary, non-dangerous side effect that improves with time as your body adapts. Never stop taking Mounjaro without consulting your GP or prescriber. If side effects are significantly affecting your quality of life, discuss this with your healthcare provider — they may suggest management strategies or adjustments rather than stopping the medication.
Is there a way to predict whether I'll get sulphur burps on Mounjaro?
Unfortunately, no reliable way to predict individual side effects before starting. Some people experience them within days; others don't at all. Factors like baseline digestion speed, diet, and individual metabolism play a role. If you're prescribed Mounjaro, discuss potential side effects with your prescriber so you know what to expect.
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