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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Mounjaro Eggy Burps vs Wegovy — What's the Difference?
Eggy burps (sulfurous belching) are a reported side effect of GLP-1 and GIP/GLP-1 weight loss injections, but experiences vary significantly between Mounjaro and Wegovy. This guide compares how often this side effect occurs with each medication, why the difference exists, and what you need to know before starting treatment. Individual responses depend on your body, dose, and how you tolerate each injection type.
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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.
How Mounjaro and Wegovy Work Differently
Wegovy (semaglutide) is a GLP-1 receptor agonist only — it activates one hormone pathway that reduces appetite and slows gastric emptying (how quickly food leaves your stomach). Mounjaro (tirzepatide) is a dual GIP and GLP-1 receptor agonist, meaning it activates two hormone pathways simultaneously. This dual mechanism may increase the likelihood of gastrointestinal side effects, including eggy burps, especially at higher doses. SURMOUNT clinical trial data showed digestive symptoms were more commonly reported with tirzepatide at maximum doses (15 mg) compared to semaglutide (2.4 mg) in STEP trials. However, individual tolerance varies considerably — some people experience no eggy burps on either medication, whilst others report them on Wegovy but not Mounjaro, or vice versa. Your GP or prescriber can discuss which mechanism might suit your body best.
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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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Side Effects and Dose Titration Strategy
Eggy burps typically emerge in the first 2–4 weeks of treatment and often improve as your body adjusts, particularly if you start at a low dose and titrate slowly. Wegovy starts at 0.25 mg and increases over 16 weeks to a maximum of 2.4 mg. Mounjaro starts at 2.5 mg and increases to a maximum of 15 mg over several months. Slower dose escalation on either medication can help minimise digestive side effects. Dietary adjustments — avoiding greasy, high-fat foods and eating smaller, more frequent meals — often reduce eggy burps. Staying hydrated and taking your injection consistently on the same day each week also helps. If eggy burps persist and significantly impact your quality of life, your prescriber may recommend pausing dose increases, switching medications, or adjusting your diet strategy before discontinuing treatment.
- 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 eggy burps more common on Mounjaro than Wegovy?
Eggy burps are more frequently reported with Mounjaro (tirzepatide) than Wegovy (semaglutide), particularly at higher doses, due to the dual GIP/GLP-1 mechanism versus single GLP-1 action. However, not everyone experiences this side effect, and it often improves within weeks as your body adjusts. Individual tolerance varies significantly.
Can you switch from Mounjaro to Wegovy if eggy burps are severe?
Yes, switching between medications is possible and may be considered if side effects become intolerable. This decision should be made with your prescriber, as switching requires a clinical assessment. Wegovy's single mechanism may suit some people better, though some experience eggy burps on Wegovy too.
How long do eggy burps typically last on Mounjaro?
Eggy burps commonly appear in weeks 2–4 after starting or increasing your dose, and typically improve within 4–8 weeks as your body adjusts. Slower dose titration (staying longer at each dose level) often reduces their severity. Some people experience them intermittently throughout treatment.
What's the difference between Mounjaro's mechanism and Wegovy's?
Wegovy activates only GLP-1 receptors, whilst Mounjaro (tirzepatide) activates both GIP and GLP-1 receptors. This dual action in Mounjaro may produce stronger appetite suppression but also increases the chance of gastrointestinal side effects like nausea, diarrhoea, and eggy burps, especially at higher doses.
Does diet affect eggy burps on weight loss injections?
Yes, significantly. High-fat, greasy foods often worsen eggy burps and other digestive symptoms on both Mounjaro and Wegovy. Eating smaller, more frequent meals and focusing on lean proteins, vegetables, and whole grains can reduce symptoms. Staying hydrated also helps. Your prescriber can refer you to a dietitian for personalised advice.
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