What it means
The FDA defines an adverse event as any undesirable experience associated with using a medical product. The word "associated" matters: an adverse event is recorded first and investigated later, so a report does not prove the product caused the problem.
An event is considered serious when it leads to death, is life-threatening, causes or lengthens a hospital stay, causes lasting disability, causes a birth defect or needs treatment to prevent permanent harm.
Clinical trials track adverse events in every group, including the placebo group. Comparing the two is how researchers work out which problems are likely caused by the drug. The tables in a drug's prescribing information come from this process.
After approval, patients and clinicians can report suspected problems to the FDA through MedWatch. Those reports help the agency spot rare risks that trials were too small or too short to catch.
Why it matters
Knowing the difference between an adverse event and a proven side effect helps you read GLP-1 safety news calmly.