Some people using GLP-1 injections for weight management, such as Mounjaro or Wegovy, notice an unusual side effect known as sulphur burps (sometimes called eggy burps).

These burps can have a strong smell, similar to rotten eggs, and may feel uncomfortable or embarrassing. While they can be unpleasant, they are usually not harmful and are a recognised digestive side effect of this type of medication.

This article explains why sulphur burps happen, how long they may last, and what you can do to manage them.

What are sulphur burps (rotten egg burps)?

Sulphur burps are caused by a gas called hydrogen sulphide, which has a strong egg-like smell. This gas is produced naturally in the digestive system when certain foods are broken down.

In some people, especially those taking GLP-1 medicines, this gas can build up more than usual and be released as burps.

Why can GLP-1 injections cause sulphur burps?

GLP-1 medicines work by copying the effects of a natural hormone in your body. While this helps reduce appetite and support weight loss, it can also change how your digestive system works.

Slower digestion

GLP-1 injections slow down how quickly food leaves the stomach. This helps you feel full for longer, but it also means food sits in the stomach for more time. When this happens, gases — including hydrogen sulphide — can form.

Changes in gut activity

Slower digestion can affect how bacteria in the gut break down food, which may increase the production of sulphur-smelling gas.

Food choices during treatment

Many people naturally change how they eat while on GLP-1 treatment. Foods that are higher in sulphur — such as eggs, meat, onions, garlic and some cabbage-family vegetables (like broccoli and cauliflower) — may make sulphur burps more noticeable for some people.

Starting treatment or increasing the dose

Sulphur burps are more commonly reported when first starting treatment or when the dose is increased, while the body is still adjusting.

Are sulphur burps a known side effect?

Yes. Digestive side effects such as nausea, bloating, belching and reflux-type symptoms are well known with GLP-1 receptor agonists.

Sulphur burps are not always listed separately in patient leaflets, but they are considered part of these digestive effects and have been reported by patients in clinical use.

How long do sulphur burps last?

For most people, sulphur burps are temporary and improve within a few weeks. As your digestive system adjusts to the medication, symptoms often settle on their own.

Some people may notice them from time to time, especially after certain foods or following a dose increase.

What can help reduce sulphur burps?

The following simple steps may help ease symptoms:

• Eat smaller meals
• Large meals take longer to digest. Smaller, more frequent meals can reduce gas build-up.
• Eat slowly and chew well
• Taking your time with meals helps digestion and may reduce burping.
• Watch trigger foods
• If symptoms are troublesome, it may help to limit foods such as:

• Eggs
• Red meat
• Onions and garlic
• Cabbage, broccoli and cauliflower
  
  

You do not need to avoid these completely — moderation is usually enough.

• Avoid fizzy drinks
• Carbonated drinks can increase gas and make burping worse.
• Stay hydrated
• Drinking enough water helps support normal digestion.
• Stay upright after eating
• Avoid lying down for at least 2–3 hours after meals to reduce reflux and burping.
  
  

When should you seek advice?

You should contact a healthcare professional if:

• Sulphur burps are severe or not improving
• You have ongoing vomiting, severe stomach pain, or difficulty swallowing
• Side effects are affecting your ability to continue treatment
  
  

Sometimes, adjusting how quickly the dose is increased can help.

Should you stop your GLP-1 medication?

Do not stop using prescription treatment without medical advice. Sulphur burps alone are usually not a reason to stop treatment, and many people find the side effect settles with time.

Speak to a healthcare professional about GLP-1 side effects

If you are experiencing sulphur burps or other side effects while using a GLP-1 injection and would like personalised advice, our clinical team can help.

Our qualified pharmacists and prescribers can discuss whether your symptoms are expected, how to manage them safely, and whether your treatment needs reviewing.

Key message

Sulphur burps (sometimes called rotten egg burps) can be an uncomfortable but usually manageable side effect of GLP-1 injections. They are linked to slower digestion — one of the ways these medicines work.

With time, small dietary changes and support from a healthcare professional, most people find symptoms improve.

Medical disclaimer

This information is provided for general guidance only and does not replace personalised medical advice. GLP-1 receptor agonists are prescription-only medicines and may not be suitable for everyone. Always follow the advice of your prescriber or pharmacist and report any concerning side effects.