Most GLP-1 side effects are gastrointestinal, dose-related, and temporary. When you start semaglutide or tirzepatide — or step up to a higher dose — the most common effects are nausea, constipation, diarrhea, and burping, because these medications slow how fast your stomach empties. For most people they ease over days to weeks as the body adjusts. A smaller number of effects are serious and need prompt medical attention. This guide explains which is which, and links to a clear, single-topic page for each. This is general information, not medical advice — talk to your prescriber about your own situation.
The common, usually temporary effects
These are expected, especially in the first weeks and after each dose increase, and usually improve with time and simple measures:
- Nausea — the most common effect; why it happens and what eases it.
- Sulfur burps — the rotten-egg burps people rarely see coming, and how to stop them.
- Diarrhea and constipation — opposite ends of the same slowed-gut story.
- Fatigue, headache, and reduced appetite — often tied to eating less; usually settle.
For the full arc, see how long GLP-1 side effects last, and for foods that ease the gut, see what to eat.
The serious effects — know these
Some symptoms are uncommon but need urgent attention, including severe abdominal pain (possible gallbladder or pancreas problems), persistent vomiting, or signs of a blocked gut. Our red-flag guide lists exactly when to stop waiting and call someone.
How we approach this
Every page here leads with the answer, cites a primary source (FDA labels, named trials, major medical centers), and is clinically reviewed. We sell nothing and recommend no vendor — see how we review.
Every clinical claim above is cited inline to a primary source. See how we review and our sourcing & fact-check standards.