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 on Mounjaro vs Wegovy: What's the Difference?
Sulphur burps (belching with an unpleasant smell) can occur with both Mounjaro and Wegovy, as both medications slow gastric emptying and affect digestion. However, the frequency and severity may differ between the two injections due to their different mechanisms of action. Understanding how each prescription weight loss injection affects your digestive system can help you and your prescriber decide which is most suitable for you. This guide compares the two based on UK clinical data and real-world experience.
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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.
Mounjaro vs Wegovy: Mechanism and GI Side Effects
Mounjaro (tirzepatide) is a dual GIP and GLP-1 receptor agonist—it activates two separate hormone pathways that regulate appetite and digestion. Wegovy (semaglutide) activates only the GLP-1 pathway. Both slow how quickly food moves from your stomach (gastric emptying), which can cause sulphur burps, bloating, constipation, and nausea.
In the SURMOUNT clinical trials, gastrointestinal side effects were very common with Mounjaro across all doses. In the STEP trials for Wegovy, similar GI effects occurred but the pattern differed slightly. Because Mounjaro works on two pathways simultaneously, some people report more intense or prolonged GI symptoms early in treatment—particularly during dose titration. Wegovy's single-mechanism approach may produce a gentler onset of GI effects for some users, though individual responses vary widely. Both medications typically cause these symptoms to improve or resolve within weeks to months of starting treatment.
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If your BMI suggests you're overweight or obese, explore our GLP-1 calculators to project potential weight loss on Mounjaro or Wegovy.
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Which Injection Causes Fewer Sulphur Burps?
There is no definitive clinical evidence showing one medication causes significantly fewer sulphur burps than the other. Both are very common side effects listed in their product information. What matters most is your individual response—some people on Mounjaro experience minimal GI upset, whilst others on Wegovy find it more troublesome.
Your prescriber will assess which medication suits your health profile, medical history, and any existing digestive conditions. If you have a history of gastroparesis or severe stomach issues, your GP or online prescriber may recommend one over the other. You can also use our free GLP-1 weight loss calculator to explore projected outcomes at different doses—side effect profiles should be discussed directly with your prescriber during your clinical assessment.
If you experience sulphur burps on either medication, practical strategies include: eating smaller, more frequent meals; avoiding high-fat and high-fibre foods initially; staying hydrated; and taking any medication doses consistently. Some people find ginger tea or simethicone (wind relief medication available over the counter) helpful. Never stop or change your dose without guidance from your prescriber. If sulphur burps are severe or persistent, contact your GP or the prescriber who issued your prescription—they may adjust your dose, suggest temporary lifestyle changes, or discuss whether the medication is still appropriate for you.
- 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.
Do both Mounjaro and Wegovy cause sulphur burps?
Yes, both can cause sulphur burps as a very common side effect. This occurs because both medications slow gastric emptying and alter how your digestive system processes food. Individual experiences vary—some people have minimal GI symptoms whilst others experience more noticeable burping, bloating, and nausea, particularly during dose titration.
Is Mounjaro more likely to cause sulphur burps than Wegovy?
There's no definitive clinical evidence showing one causes significantly more sulphur burps than the other. Both list GI symptoms as very common side effects. Mounjaro's dual mechanism (GIP + GLP-1) may cause slightly more intense early GI effects for some people, but individual responses are highly variable. Your prescriber can advise which suits you best.
How long do sulphur burps last on Mounjaro or Wegovy?
Most people find sulphur burps improve within 2–4 weeks as your body adapts to the medication. Some report continued mild symptoms, whilst others experience complete resolution. If burps persist beyond 8–12 weeks or worsen, speak to your prescriber—adjusting your dose or meal timing may help.
Can I reduce sulphur burps whilst taking Mounjaro or Wegovy?
Yes. Eat smaller, more frequent meals; avoid high-fat and high-fibre foods initially; stay hydrated; and take your injection on a consistent day each week. Over-the-counter wind relief (simethicone) or ginger tea may also help. Always consult your prescriber before changing your diet significantly.
Which medication should I choose if I'm worried about sulphur burps?
This depends on your individual health profile, which only a licensed prescriber can assess through a clinical consultation. Both Mounjaro and Wegovy require a UK prescription and clinical assessment. Discuss your concerns about GI side effects with your prescriber—they'll help determine which medication (if either) is appropriate for you based on your medical history.
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