What are GLP-1 Receptor Agonists and How Do They Work?

The recent price rise news of Mounjaro in the UK has been difficult for many people. If you’re feeling worried or uncertain about what this means for your treatment, you’re not alone.

Because of these changes, a growing number of people are now considering alternatives such as Wegovy (semaglutide). Wegovy is often more affordable, and studies have shown that at higher doses it can lead to weight loss of up to 20%.

Still, it’s important to remember that Mounjaro and Wegovy are not the same medication. Each works differently, and switching from one to the other needs careful thought and planning with the right support.

To make things a little easier, we’ve pulled together the key things you should know before making a decision.

Mounjaro vs Wegovy: The Key Differences

• Mounjaro (tirzepatide): Acts on both GLP-1 and GIP receptors, which may make it particularly effective for appetite suppression and glucose control.
  
• Wegovy (semaglutide): Works only on the GLP-1 receptor, a well-studied pathway for weight management and type 2 diabetes. Recent data suggest that Wegovy at higher doses can deliver average weight loss of around 15–20%, rivalling or even exceeding some reports for Mounjaro.

Because of these differences, there isn’t a direct like-for-like conversion between the two medicines. Instead, clinicians use approximate dose equivalents when making the switch.

Available Doses

Mounjaro is available in the following dose strengths (weekly injections):

• 2.5 mg
• 5 mg
• 7.5 mg
• 10 mg
• 12.5 mg
• 15 mg

Wegovy is available in these weekly dose strengths:

• 0.25 mg
• 0.5 mg
• 1.0 mg
• 1.7 mg
• 2.4 mg (maintenance dose)
  
  

Switching Dose Guide

At Shemed, we understand that switching between treatments can feel overwhelming, and many people want clear answers. However, there is no strict dose conversion between Mounjaro and Wegovy. The choice of starting dose when switching should always be made by a qualified healthcare professional, taking into account your current treatment, medical history, and individual response.

⚠️ Important: Please don’t feel you need to figure this out on your own. Do not attempt to switch or calculate equivalent doses without support. Always follow the advice of your prescribing clinician, who will guide you safely through the transition and answer any questions you may have.

Timing the Switch

At SheMed we recommend:

• Wait around 7 days after your last Mounjaro injection before starting Wegovy. This helps to minimise overlapping effects and reduces side-effect risks such as nausea or bloating.

Titration and Side Effects

At Shemed, your clinician will decide which starting dose of Wegovy is most suitable for you. Titration - that is, gradually increasing the dose over time - will be required to minimise side effects and ensure your body adjusts safely. The exact schedule will vary depending on your individual circumstances, and your prescribing clinician will guide you through this process step by step.

Common side effects during the switch can include:

• Nausea
• Bloating
• Diarrhoea or constipation
• Tiredness

These usually improve as your body adjusts, and your clinician will be on hand to support you if side effects persist or feel difficult to manage.

What to Expect After Switching

• Effectiveness: Some patients notice slightly different appetite suppression on Wegovy compared to Mounjaro, due to their differing mechanisms of action.
  
• No withdrawal symptoms: Stopping Mounjaro does not cause withdrawal, but you may feel a change in appetite control during the transition.
  
• Follow-up: Your clinician will likely schedule a review monthly after starting Wegovy to monitor your progress and adjust dosing.
  

Key Takeaways

• Rising Mounjaro prices in the UK mean many people are now considering Wegovy as a cost-effective alternative.
  
• Wegovy has been shown to deliver up to 20% weight loss at higher doses in recent studies.
  
• A minimum 7-day gap is typically recommended before starting Wegovy. 
  
• Dose equivalents provide a starting point, but titration is still necessary.
  
• Always work with your healthcare professional to personalise your transition.
  

Need Support?

If you are considering switching from Mounjaro to Wegovy and would like tailored advice, our clinicians at Shemed are here to help. You can reach us at support@shemed.com for guidance and support with your treatment journey.

Have you recently started Mounjaro and found yourself dealing with unexpected and uncomfortable belching that smells a bit like rotten eggs? If so, you're not alone - and you're certainly not imagining it. These “sulphur burps” can be distressing, especially when you're otherwise motivated and hopeful about your weight loss journey.

Based on a survey in the UK, many patients reported that they felt blindsided by this peculiar side effect. One minute, they’re feeling hopeful with a powerful new weight loss injection, and the next, they’re wondering if something’s gone wrong with their digestive system. And perhaps you're wondering the same - Is this normal? Will it go away? And what can I do about it?

This guide was created to address those very concerns. We’ll explore why Mounjaro (tirzepatide) might cause sulfur burps, how common and manageable this issue is, and what you can do to ease the discomfort without compromising your progress. Let's unpack the science behind it and, more importantly, the practical ways to feel better.

Mounjaro (Tirzepatide) 

Mounjaro has quickly become one of the most talked-about advances in the treatment of obesity and type 2 diabetes. Approved by MHRA, it has brought fresh hope to individuals struggling with weight loss and metabolic health.

Its arrival on the NHS and in private weight loss clinics has been met with enthusiasm, especially because of its dual-action mechanism that promotes both improved blood sugar control and significant weight loss. For many, it offers the possibility of reclaiming health, mobility, and confidence.

But with all medications, especially newer ones, there can be surprises. One of these is gastrointestinal discomfort, and in particular, foul-smelling burps that some describe as tasting or smelling like sulphur. While not dangerous, they can be off-putting and even socially disruptive.

Understanding How Mounjaro Works

To understand why such a symptom might occur, it helps to know a bit about how Mounjaro functions in the body. Tirzepatide is what we call a dual incretin agonist. It mimics the actions of two naturally occurring gut hormones - GLP-1 (glucagon-like peptide-1) and GIP (glucose-dependent insulinotropic polypeptide). Together, these hormones help regulate blood sugar after eating, reduce appetite, and, importantly, slow down how quickly food moves through the stomach.

This slowing down of digestion is beneficial for weight loss, as it helps you feel fuller for longer and keeps post-meal blood sugars steady. But it can also lead to side effects, including nausea, bloating, and in some cases, excessive or unpleasant-smelling burping.

Mounjaro is approved for use in adults with type 2 diabetes and weight loss in individuals with a BMI of 30 or more, or 27 with weight-related health conditions. It should always be prescribed and monitored by a qualified healthcare professional who can guide you through its benefits and potential challenges.

What Are Sulphur Burps and Why Do They Happen?

Sulphur burps - sometimes called rotten egg burps - occur when gas containing hydrogen sulfide is released from the stomach and expelled through belching. The smell is distinctive and often compared to decaying eggs. It's not harmful in small amounts, but it can be unpleasant and, for some, embarrassing.

Patients describe them as sudden, foul-smelling belches that seem to come out of nowhere, sometimes accompanied by a sour or metallic taste. They can happen after meals or even on an empty stomach, and in some cases, they disrupt sleep or social activities.

Although they aren’t included as a common side effect in Mounjaro’s official safety profile, reports of sulphur burps have emerged among users, particularly those in online forums, weight loss support groups, and anecdotal clinic feedback. While not everyone will experience them, they are a recognised concern and likely tied to how the medication alters digestion.

Real-World Experiences

• User Feedback: Sulphur burps are frequently discussed in patient forums and social media. Experiences vary from mild annoyance to severe discomfort, but most participants note improvement with dietary or behavioural adjustments.
• Related Symptoms: Some users report sulphur burps alongside stomach discomfort, diarrhoea, or bloating, especially after dose changes.

The Link Between Mounjaro and Sulphur Burps: What's Going On Inside Your Gut?

One of Mounjaro’s main effects is slowing gastric emptying. That means food stays in your stomach and upper digestive tract longer than usual. While this helps you feel full and eat less, it also gives gut bacteria more time to break down the food, especially proteins and certain carbohydrates. When this bacterial fermentation happens, it can release gases like methane, hydrogen, and hydrogen sulfide.

Hydrogen sulfide is the culprit behind the rotten egg smell. The risk of producing this gas increases if your diet contains a lot of high-sulphur foods - think eggs, onions, garlic, cruciferous vegetables like cabbage and broccoli, red meats, and certain dairy products. Add in high-fat meals, which can slow digestion even further, and the stage is set for fermentation and gas production.

It's also important to note that every individual has a unique gut microbiome. Some people naturally have more sulphur-producing bacteria, which might explain why only certain individuals experience this side effect on Mounjaro, even when eating similar diets.

Managing Sulphur Burps While on Mounjaro: What You Can Do?

If you’re dealing with sulphur burps while taking Mounjaro, you don’t need to suffer in silence. There are several practical ways to ease the issue without having to stop the medication.

• One of the most effective first steps is to look at your diet. Reducing your intake of sulphur-rich foods can make a noticeable difference. You might not need to eliminate them, but cutting back on frequent servings of eggs, red meats, onions, and cruciferous vegetables for a few weeks may help reduce the smell and frequency of burps. 

Similarly, opting for lighter, lower-fat meals can support faster digestion. Eating smaller meals more frequently throughout the day may prevent your stomach from becoming overly full and reduce the fermentation time.

• Hydration is another simple but powerful strategy. Drinking enough water helps support digestion and gut motility. Some people also find that warm fluids like herbal teas ease bloating and burping.
• Chewing food thoroughly and eating slowly reduces the amount of air swallowed during meals, which can help prevent excessive gas formation. Avoid fizzy drinks and don’t talk with your mouth full - both introduce unnecessary air into the digestive tract.

When Remedies Can Help: Medicines and Supplements

If dietary changes and mindful eating don’t fully resolve the issue, certain over-the-counter remedies may offer relief, but they should be used with guidance from your pharmacist or GP.

Simethicone-based products such as Wind-eze can help break up gas bubbles in the gut, making it easier for your body to expel them naturally. It also comes in our SheMed support pack.

Some people find benefit in taking probiotics, which can help rebalance gut bacteria. Not all probiotic strains are effective for this purpose, so look for ones supported by evidence in digestive health - your pharmacist or dietitian can recommend appropriate UK-approved brands.

Another option is bismuth subsalicylate (like Pepto-Bismol), which can bind to hydrogen sulfide and neutralise the smell. However, this should only be used occasionally and with medical guidance, especially if you’re on other medications, as it can interact with drugs.

Activated charcoal is sometimes suggested, but it can also bind to medications and nutrients, interfering with absorption. It's best to approach this option cautiously and only after speaking with your doctor.

When to Speak to Your Doctor: Knowing What’s Normal and What’s Not

While sulphur burps are usually a benign and manageable side effect, there are situations where you should seek medical advice. If your symptoms become persistent, worsen over time, or start to impact your daily life, speak to your GP or prescribing clinician. You may need a review of your dosage, further dietary support, or even a check for other digestive issues such as gastritis or bacterial overgrowth.

In some cases, sulphur burps could be a sign of an underlying gastrointestinal condition, particularly if they’re accompanied by red flag symptoms like severe abdominal pain, ongoing nausea or vomiting, diarrhoea or constipation, fever, unexplained weight loss, or blood in your stool or vomit.

Don’t wait to report these symptoms. Mounjaro may need to be paused or adjusted, and your doctor can ensure there’s nothing more serious occurring in the background.

Conclusion

Starting Mounjaro is a significant and often hopeful step in addressing weight or metabolic health challenges. While it can come with surprises like sulphur burps, it’s important to remember that most side effects are manageable - and often temporary. You don’t have to choose between relief and results. 

With the right strategies, support, and awareness, you can continue progressing on your weight loss journey without being held back by uncomfortable symptoms. Stay in regular touch with your healthcare team. 

Don’t hesitate to ask questions or voice concerns, especially about digestive side effects. You are not alone, and your concerns are valid. Mounjaro is one tool in a broader toolkit that includes lifestyle changes, nutrition, movement, and mental well-being. Together, these elements can help you achieve your goals in a sustainable, empowered way.

FAQs

1. Are sulphur burps a normal side effect of Mounjaro?

While not officially listed as a common side effect in clinical trials, sulphur burps have been reported by some Mounjaro users. They are likely linked to the way the medication slows digestion, which can increase gas production in the gut. The symptom is usually manageable and not harmful.

2. What foods should I avoid if I’m experiencing sulphur burps on Mounjaro?

Reducing foods high in sulphur - like eggs, onions, garlic, cabbage, broccoli, and red meat - may help. Limiting high-fat meals and fizzy drinks can also reduce burping. Keeping a food diary can be useful for identifying personal triggers.

3. Do I need to stop taking Mounjaro if I have sulphur burps?

Not usually. Most cases improve with dietary changes and supportive measures. However, if the symptoms are severe, persistent, or affecting your quality of life, speak to your prescribing doctor. They may suggest adjustments or further assessment.

References

1. British National Formulary (BNF). (2024). Tirzepatide: Drug monograph. Retrieved from https://bnf.nice.org.uk/drugs/tirzepatid
   
2. Mayo Clinic. (2023). Sulfur burps: Causes and remedies. Retrieved from https://www.mayoclinic.org/diseases-conditions/gas-and-gas-pains/in-depth/gas-and-gas-pains/art-20044739
   
3. MedlinePlus. (2024). Tirzepatide injection. U.S. National Library of Medicine. Retrieved from https://medlineplus.gov/druginfo/meds/a623037.html (Note: URL verified through U.S. National Library of Medicine) ‍
4. Monash University. (2022). Gut microbiome and digestion. Monash FODMAP Diet. Retrieved from https://www.monashfodmap.com/ 
5. NHS (2024). GLP‑1 receptor agonists: Side effects and safety. Retrieved from https://www.nhs.uk/medicines/glp-1-receptor-agonists/ 
6. Zhou, M., Wang, X., Li, J., & Liu, Y. (2023). Gastrointestinal side effects of GLP‑1 and GIP receptor agonists: Mechanisms and management. Pharmacological Research, 190, 106719. https://doi.org/10.1016/j.phrs.2023.106719

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