US Medical Term · clinical
Adverse Event
Evento Adverso
In 9 languages
| Language | Term |
|---|---|
| English | Adverse Event |
| Spanish (Español) | Evento Adverso |
| Chinese (中文) | 不良事件 |
| Korean (한국어) | 이상 반응 |
| Vietnamese (Tiếng Việt) | Sự cố bất lợi |
| Filipino (Tagalog) | Masamang Kaganapan |
| Portuguese (Português) | Evento Adverso |
| Thai (ภาษาไทย) | เหตุการณ์ไม่พึงประสงค์ |
| Japanese (日本語) | 有害事象 |
What it means
An adverse event is any unexpected or harmful medical occurrence that happens during or after a medical treatment, drug therapy, or clinical trial—whether or not it is caused by the treatment itself. Examples include an unexpected drug side effect, an allergic reaction, a fall in the hospital, or a new symptom that develops during a study. Healthcare providers and clinical trial sponsors are required to report serious adverse events to the FDA and relevant oversight boards. If you experience an unexpected health problem during treatment, report it to your doctor immediately. You may also file a report with the FDA's MedWatch program. Adverse events can affect your insurance coverage if the event leads to additional medical care.
How to say it
Sentences a patient might use with a doctor, nurse, pharmacist, or insurer:
I reported an adverse event to my doctor after starting the new medication.
Informé un evento adverso a mi médico después de comenzar el nuevo medicamento.
The clinical trial team said they must report any adverse event to the FDA.
El equipo del ensayo clínico dijo que deben reportar cualquier evento adverso a la FDA.
My insurer denied the claim, saying the hospitalization was due to an adverse event.
Mi aseguradora negó el reclamo, diciendo que la hospitalización fue por un evento adverso.
Where you'll see it
Related terms
Sources
Last reviewed: September 2026