Why Does Mounjaro Cause Gallbladder Issues?

Gallbladder issues and gallstones

Mounjaro works as a dual GIP and GLP-1 receptor agonist, which slows the movement of food through the digestive system and reduces appetite. One consequence of this slowed motility is that bile — the digestive fluid stored in the gallbladder — may sit stagnant for longer. When bile becomes concentrated and stagnant, it is more likely to form crystals or stones. Additionally, when weight is lost relatively quickly, the liver releases extra cholesterol into bile, which further raises the risk. According to NHS guidance, gallstone risk is a known consideration with this class of medicines, and your prescriber or doctor should be aware of any relevant history you have.

If you experience sudden, severe pain in the upper right abdomen, fever, or yellowing of the skin or eyes, contact a healthcare professional promptly — do not wait for your next scheduled appointment. You can read more about how tirzepatide works in the body on our overview of how Mounjaro works.

Why Mounjaro causes nausea

Nausea is one of the most commonly reported side effects of Mounjaro. Tirzepatide slows gastric emptying — food leaves the stomach more slowly than usual — which many people experience as a feeling of fullness that tips into queasiness, particularly around the time of a dose increase. For many people this eases as the body adjusts over several weeks, though it may return with each step up in dose.

Why Mounjaro causes constipation

The same slowing of gut motility that affects the stomach also affects the bowel. Food and waste move through more slowly, which commonly results in constipation. Staying well hydrated and maintaining fibre intake can help, though any persistent or severe changes in bowel habit are worth discussing with your prescriber or doctor.

Why Mounjaro causes headaches

Headaches are commonly reported, particularly in the early weeks. Reduced appetite can mean some people eat and drink less than usual, and mild dehydration or a dip in calorie intake may contribute. There may also be a direct effect via GLP-1 receptors present in the brain, though the precise mechanism is still being studied.

Why Mounjaro causes sulphur burps

The slowing of gastric emptying means food ferments in the stomach for longer, which can produce sulphur-smelling gas. This is unpleasant but generally harmless, and many people find it eases once their body adapts to the medicine. You may notice it is worse after protein-rich meals.

Why Mounjaro may affect mood or anxiety

Some people report changes in mood, low mood, or heightened anxiety while taking Mounjaro. GLP-1 receptors are found in areas of the brain involved in mood regulation, and significant changes to appetite, energy, and daily routine can also play a role. If you experience notable changes in your mental health, contact your prescriber or doctor — do not dismiss these as minor. Our page on other side effect questions covers additional concerns some people raise, and you may also find our page on feeling cold on Mounjaro useful if you have noticed that effect too.

When side effects are happening across several body systems at once, it can be hard to remember which symptoms appeared when, how severe they were, and whether they are improving. GLP Trackr's side-effect tracking feature lets you log individual symptoms — nausea, digestive discomfort, headaches, mood changes, and more — each day, so patterns become visible over time rather than relying on memory.

That log becomes genuinely useful at prescriber appointments: instead of a vague "I felt rough for a while", you have a clear record of what happened, when, and how it changed. The app also lets you note the date and dose of each injection, which helps you and your prescriber connect symptoms to dose stages — useful context when deciding whether an effect is settling or worth investigating further. If you notice something worrying, you can also use the doctor report feature to share a summary of your tracked data.

GLP Trackr is not a substitute for your prescriber or doctor's advice, and it does not interpret your symptoms clinically. If any side effect is severe, persistent, or worrying — especially upper abdominal pain, significant mood changes, or anything that feels urgent — please contact a healthcare professional promptly. Any suspected side effects can also be reported through your national reporting scheme (such as the UK's Yellow Card scheme or its equivalent in your country).

You can find a broader explanation of tirzepatide's mechanisms on our guide to how Mounjaro works, and explore related questions such as whether Mounjaro causes yeast infections.

Log your symptoms as they happen and build a picture your prescriber can actually use — GLP Trackr is free to try for 7 days on the App Store and Google Play.