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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Sulphur Burps With Mounjaro: Causes, Management & UK Access
Sulphur burps (rotten egg-like burps) are one of the more unpleasant side effects some people experience when taking Mounjaro (tirzepatide), a prescription-only weight management injection. This happens because Mounjaro slows how quickly food moves through your stomach, which can cause gas and digestive discomfort. The good news is that this side effect typically improves over time as your body adjusts to the medication. Understanding what causes sulphur burps, how to manage them, and what your options are for accessing Mounjaro in the UK can help you make an informed decision about whether this medication is right for you.
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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.
What Causes Sulphur Burps on Mounjaro?
Sulphur burps occur because Mounjaro slows gastric emptying — the rate at which food leaves your stomach. When food sits in your stomach longer, bacteria break it down and produce hydrogen sulphide gas, which smells like rotten eggs. This is a very common side effect, particularly in the first 4–8 weeks when you're adjusting to the medication or increasing your dose.
The effect typically lessens as your body adapts, though some people experience it intermittently throughout treatment. Other related digestive side effects include nausea, diarrhoea, constipation, and general stomach discomfort. These are all listed as very common side effects in Mounjaro clinical trials — affecting more than 1 in 10 people.
- Most pronounced when starting or increasing dose
- Improves within weeks as your body adjusts
- Related to slower stomach emptying (a key way Mounjaro works)
- Often improves with dietary adjustments and time
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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.
Accessing Mounjaro in the UK: NHS vs Private Routes
In the UK, you can access Mounjaro through two main routes: NHS specialist services or private online prescribing. NHS access is through tier 3 specialist weight management services (requires GP referral), though availability and waiting times vary significantly by region. Private prescribing offers faster access — you complete an online consultation with a UK-licensed prescriber, and if approved, receive a prescription dispensed by a GPhC-registered pharmacy.
Mounjaro typically costs between £130–£300 per month privately, depending on your dose. The Mounjaro KwikPen comes in doses from 2.5 mg up to 15 mg, with each pen lasting 4 weeks. Use our free GLP-1 weight loss calculator to explore potential outcomes and help you decide if Mounjaro is right for you alongside any cost consideration.
- 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 on Mounjaro?
Sulphur burps typically improve within 4–8 weeks as your body adjusts to Mounjaro. For some people they resolve completely; others experience them intermittently. If they persist beyond 8 weeks, speak to your prescriber — dietary changes or dose adjustments may help.
Can I reduce sulphur burps while taking Mounjaro?
Yes. Eat smaller, more frequent meals, avoid high-fat and high-sugar foods (which slow digestion further), stay well hydrated, and increase fibre gradually. Some people find ginger tea or peppermint helpful. Probiotics may also support gut health, though evidence is limited.
How much does Mounjaro cost privately in the UK?
Private Mounjaro typically costs £130–£300 per month depending on your dose and provider. Starting doses (2.5–5 mg) are usually cheaper; maintenance doses (10–15 mg) are more expensive. Prices vary between providers, so it's worth comparing.
Is Mounjaro available on the NHS in the UK?
Yes, Mounjaro is NICE-approved for NHS use through specialist tier 3 weight management services. However, access requires GP referral and availability varies by region. NHS waiting lists can be very long — some areas have waits of months or even years.
What's the difference between Mounjaro and Wegovy for side effects?
Both cause similar digestive side effects including sulphur burps, nausea, and diarrhoea. Mounjaro (tirzepatide) is a dual GIP and GLP-1 agonist; Wegovy (semaglutide) is a GLP-1 agonist only. Some people experience fewer sulphur burps on one vs the other — individual responses vary significantly.
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.