Know the common stomach effects
Common unwanted effects in semaglutide weight-loss trials include vomiting and feeling sick, as well as loose stools and difficulty passing stool.
Diarrhea means loose or watery stools; constipation means trouble passing stool.
Repeated vomiting or diarrhea can lead to fluid loss and kidney harm.
Ask the prescriber how to report symptoms and when they want to hear from you. Keep that plan somewhere easy to find.
Get help for severe symptoms
The medicine's official warning describes severe belly pain that does not ease and may spread to the back. This can be a sign of pancreatitis, a serious illness with swelling and pain.
Seek urgent medical help for that kind of pain.
Trouble breathing or swelling of the tongue or face can be signs of a severe allergic reaction.
Get emergency help right away for these severe symptoms.
These are reasons to get help, rather than a checklist for deciding what illness you have.
Raise these health details before treatment
The official medicine information says you must not use semaglutide if medullary thyroid cancer has affected you or someone in your family; this is a rare type of thyroid cancer.
Treatment is also ruled out for MEN 2, a rare illness that can pass down through families. Treatment is also ruled out if semaglutide or any of its ingredients has caused a serious allergy before.
Ask the prescriber to check for MEN 2 in your health records and the names of illnesses in your family. Bring any old letters about those illnesses; there is no need to recognise the initials yourself.
The semaglutide (Wegovy) medicine information does not recommend treatment for severe gastroparesis, where the stomach takes far too long to empty.
Mention pregnancy plans, diabetes medicines, eye trouble linked to diabetes, past pancreatitis or gallbladder problems and planned surgery to the prescriber.
The medicine information asks patients taking semaglutide to tell the surgical team before a planned procedure.
The source link below opens the full medicine information, with these warnings. You can also ask the prescriber or pharmacist for a copy.
A closer look at the source
What the thyroid warning does, and does not, say
The official semaglutide medicine information puts its strongest warning in a box, about thyroid tumors.
Rats and mice developed these tumors in tests. It is still unknown whether semaglutide causes them in people.
That uncertainty is a reason to discuss your history, rather than read the warning as proof either way.
Information as of September 26, 2026.