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
How Long Do Sulphur Burps Last on Mounjaro?
Sulphur burps (rotten egg burps) are a common digestive side effect of Mounjaro and other GLP-1 weight loss medications. Most people experience them during the early weeks of treatment or when increasing their dose, and they typically subside within 2–4 weeks as the body adjusts. However, duration varies between individuals — some notice improvement within days, while others may experience them for longer. Understanding what causes them and how to manage them can help you feel more confident during treatment.
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.
Why Sulphur Burps Happen on Mounjaro vs Wegovy
Sulphur burps occur because both Mounjaro (tirzepatide) and Wegovy (semaglutide) slow gastric emptying — how quickly food moves from your stomach into the small intestine. When food sits in the stomach longer, bacteria ferment undigested food, producing hydrogen sulphide gas, which creates that distinctive rotten egg smell. This effect is more pronounced when starting treatment or increasing your dose.
Interestingly, Mounjaro's dual GIP and GLP-1 mechanism may cause this side effect slightly more frequently than Wegovy's single GLP-1 pathway, based on clinical trial data from SURMOUNT and STEP trials. However, individual experience varies considerably. Both medications' effect on gastric emptying typically reduces over time — usually after 4–12 weeks — as your body adapts, which is why sulphur burps are often a temporary adjustment symptom rather than a permanent side effect.
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.
Managing Sulphur Burps and Timeline Expectations
Most people find sulphur burps improve within 2–4 weeks of starting Mounjaro or when their dose increases. To help reduce them, eat smaller, more frequent meals; avoid fatty or greasy foods that digest more slowly; stay hydrated; and consider ginger tea or peppermint, which may aid digestion. If they persist beyond 8 weeks, speak to your prescriber — occasionally, a temporary dose reduction or interval adjustment can help. Remember, this side effect typically indicates your medication is working, as the slowed digestion is part of how these medications support weight loss. Your GP or prescriber can advise whether your specific experience is within normal adjustment and suggest personalised strategies.
- 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.
How long do sulphur burps last when starting Mounjaro?
Most people experience sulphur burps for 2–4 weeks after starting Mounjaro or increasing their dose, as the body adjusts to slowed gastric emptying. However, some notice improvement within days, while others may experience them for up to 8 weeks. Individual timelines vary based on dose, metabolism, and diet.
Are sulphur burps worse on Mounjaro than Wegovy?
Clinical data suggests Mounjaro (tirzepatide's dual mechanism) may cause sulphur burps slightly more frequently than Wegovy (semaglutide's single GLP-1 pathway), but individual experiences vary significantly. Both medications slow stomach emptying, causing this side effect. Your personal experience depends more on your body's adjustment than on which medication you use.
What can I do to reduce sulphur burps on Mounjaro?
Eat smaller, frequent meals; avoid fatty or greasy foods; stay well hydrated; try ginger or peppermint tea; and eat slowly. These changes help your digestive system work more efficiently. If sulphur burps persist beyond 8 weeks, speak to your prescriber about your individual situation.
Should I stop Mounjaro if I have sulphur burps?
No — sulphur burps are a common, temporary adjustment side effect and do not mean the medication is unsafe. They typically resolve within weeks as your body adapts. Continue your treatment as prescribed unless your prescriber advises otherwise. If they cause significant distress, speak to your GP.
Will sulphur burps come back if I increase my Mounjaro dose?
Yes, they may. Each dose increase can temporarily cause or worsen sulphur burps as your body readjusts to the new dose level. This usually settles within 1–4 weeks. Your prescriber increases doses gradually (typically every 4 weeks) to allow your system to adapt.
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.