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
Understanding Mounjaro and Eggy Burps
Eggy burps (burping with a sulphur-like smell) are a reported side effect some people experience when taking Mounjaro (tirzepatide), though they're not mentioned in the official patient information. This occurs because Mounjaro slows how quickly food moves through your stomach, which can cause fermentation and gas. Understanding how this compares to other GLP-1 medications like Wegovy can help you decide which prescription weight loss treatment might suit you best. If you experience this side effect, your GP can offer practical advice and reassurance.
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.
How Mounjaro and Wegovy Differ in Side Effects
Mounjaro (tirzepatide) is a dual GIP and GLP-1 receptor agonist, whereas Wegovy (semaglutide) is a GLP-1 receptor agonist only. This difference in mechanism may explain why some side effects are reported more frequently with one medication than the other. Both slow gastric emptying (how quickly food leaves your stomach), which can cause digestive side effects including nausea, diarrhoea, constipation, and abdominal discomfort. Eggy burps appear more commonly reported in real-world use with Mounjaro than Wegovy, likely because of the dual hormone pathway activation and the resulting digestive changes. According to SURMOUNT and STEP clinical trials, both medications caused similar overall gastrointestinal side effects, though the character and timing of symptoms varies between individuals. Your prescriber or GP can discuss which medication's side effect profile may suit your personal health situation better.
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 Eggy Burps and Other Mounjaro Digestive Effects
If you develop eggy burps on Mounjaro, practical steps include eating smaller, more frequent meals, avoiding foods that ferment easily (such as beans, carbonated drinks, and high-fat foods), staying well hydrated, and eating slowly. Many people find the symptom improves as their body adjusts to the medication over the first few weeks. If eggy burps persist beyond the initial adjustment period or become distressing, contact your GP or the prescriber who issued your Mounjaro UK prescription. They may adjust your dose, recommend digestive support, or discuss switching to an alternative medication like Wegovy. Use our free GLP-1 weight loss calculator to compare projected outcomes at different doses, and track your side effects alongside your progress using our progress tracker tool—this helps identify patterns and informs conversations with your healthcare team.
- 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.
Why do some people get eggy burps on Mounjaro but not Wegovy?
Mounjaro's dual GIP and GLP-1 mechanism may cause more pronounced digestive changes than Wegovy's single GLP-1 pathway. Both slow stomach emptying, but Mounjaro's additional GIP activation can increase gas production and fermentation in the stomach, leading to eggy burps. Individual digestive systems respond differently—not everyone experiences this.
Are eggy burps a sign that Mounjaro isn't working?
No. Eggy burps are a side effect of how the medication alters digestion, not an indicator of effectiveness. Many people who experience this side effect still achieve significant weight loss. The symptom often improves within 2–4 weeks as your body adjusts. If concerned, discuss with your GP.
Can I stop Mounjaro if I get eggy burps?
You should not stop taking Mounjaro without medical guidance. Contact your prescriber or GP first. They can advise whether to adjust your dose, try practical management strategies, or consider an alternative medication. Stopping suddenly may affect your weight management plan.
Is Wegovy a better option than Mounjaro if I'm worried about side effects?
Not necessarily. Whilst some people report fewer digestive side effects with Wegovy, others experience the same symptoms with both medications. Side effect tolerance is individual. Your prescriber will assess which medication suits you best based on your medical history, eligibility, and personal health factors. Both require clinical assessment.
How long do eggy burps last on Mounjaro?
For many people, eggy burps reduce or resolve within 2–4 weeks as the body adjusts. Others may experience them longer or intermittently throughout treatment. If they persist beyond 4–6 weeks or significantly affect quality of life, discuss with your GP or prescriber about management options or medication alternatives.
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.