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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Understanding Eggy Burps on Mounjaro — UK Health Information
Eggy burps (belching with a rotten egg or sulphur smell) are a recognised gastrointestinal side effect reported by some people taking Mounjaro (tirzepatide) in the UK. This occurs because Mounjaro slows how quickly food moves through your stomach, which can affect digestive processes. While uncomfortable, this side effect is typically temporary and often improves as your body adjusts to the medication. If you're considering Mounjaro through NHS specialist services or privately, understanding potential side effects helps you make an informed decision with your prescriber.
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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.
How Mounjaro Causes Eggy Burps and NHS Eligibility
Why eggy burps happen: Mounjaro is a dual GIP and GLP-1 receptor agonist that slows gastric emptying—the rate at which food leaves your stomach. This delayed digestion can alter how your gut bacteria ferment food, producing sulphur compounds that cause the characteristic rotten egg smell when you burp. This effect is often most noticeable in the first few weeks as your body adjusts.
NHS eligibility for Mounjaro: In the UK, Mounjaro is available through NHS tier 3 specialist weight management services for adults with a BMI of 30 or above, or 27–29.9 with weight-related health conditions like type 2 diabetes or cardiovascular disease. NICE has approved tirzepatide for NHS use, though regional availability and waiting times vary significantly. Your GP can refer you to your local specialist service, which will assess whether this medication is suitable for you, including discussing potential side effects like eggy burps.
- Slowed gastric emptying effect typically reduces over time
- More common in early weeks of treatment
- May be managed by dietary adjustments
- NHS prescribing through specialist services only
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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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Managing Eggy Burps and NHS vs Private Routes
Most people find eggy burps improve within 2–4 weeks as their digestive system adapts, though individual experiences vary. Dietary strategies can help—avoiding sulphur-rich foods (eggs, cruciferous vegetables, dairy), eating smaller meals, and staying hydrated may reduce symptoms. If you're prescribed Mounjaro via NHS tier 3 services, your specialist team can provide ongoing support and adjustments. For those accessing Mounjaro privately after clinical assessment, your prescriber will discuss side effect management strategies. The GLP-1 weight loss calculator on this page can help you understand projected outcomes, while tracking side effects alongside weight loss progress gives you a complete picture of how Mounjaro affects your individual health.
- 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 eggy burps last when taking Mounjaro?
Eggy burps typically appear in the first 1–2 weeks of starting Mounjaro and often improve significantly within 2–4 weeks as your digestive system adapts to the medication. However, some people experience them intermittently throughout treatment. Duration varies between individuals, and your NHS specialist or prescriber can advise if they persist.
Are eggy burps a sign that Mounjaro isn't working?
No. Eggy burps are a side effect of how Mounjaro slows your stomach's digestion, not a sign of treatment failure. Many people who experience this side effect still achieve good weight loss results. The two are independent—side effects and efficacy don't necessarily correlate.
Can I reduce eggy burps by changing my diet?
Yes. Limiting sulphur-rich foods like eggs, broccoli, cauliflower, onions, and dairy may help. Eating smaller, more frequent meals, drinking plenty of water, and chewing food thoroughly can also support better digestion. Your GP or dietitian can provide personalised dietary advice.
Is there a difference between Mounjaro eggy burps and Wegovy eggy burps?
Both Mounjaro and Wegovy slow gastric emptying, so eggy burps can occur with both. However, Mounjaro (tirzepatide) is a dual GIP and GLP-1 agonist while Wegovy (semaglutide) is a GLP-1 agonist only. Some people report different side effect profiles, but experiences vary widely between individuals.
Can my NHS GP prescribe Mounjaro if I have eggy burps?
Your GP cannot directly prescribe Mounjaro—it must come through NHS tier 3 specialist weight management services. If you're experiencing side effects, your specialist team will work with you to manage them. You can also discuss eggy burps at your next appointment; your team may adjust your dose or provide management strategies.
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.