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Side Effect: Fainting (Syncope)

What is Fainting (Syncope)?

Fainting, also known as syncope, is a temporary loss of consciousness due to a decrease in blood flow to the brain.

It is often triggered by a sudden drop in blood pressure or heart rate, leading to a lack of oxygen in the brain.

What does Fainting (Syncope) look like?

Fainting can look different in different people, but some common signs and symptoms that might be felt right before fainting include:

Who is at risk for Fainting (or experiencing syncope)?

While fainting is not a common symptom of cancer itself, patients may experience fainting due to the underlying medical conditions or the treatments they are receiving. For example, if your treatment causes dehydration, anemia, low blood sugar, or low blood pressure you might also be at risk of fainting.

Some therapies also increase risk of orthostatic hypotension which is when a sudden drop in blood pressure occurs when standing after laying down or being in a seated position.

How to prevent Fainting (Syncope)

To prevent fainting, it can be helpful to stay hydrated, avoid standing or sitting for long periods of time, and to try not to change positions too quickly. These types of preventative measures help to keep the blood pressure normal, and an adequate amount of blood flowing to the brain.

How to treat Fainting (Syncope)


1. Soteriades ES, Evans JC, Larson MG, et al. Incidence and prognosis of syncope. N Engl J Med 2002;347(12):878-885.

Created: May 18, 2024 Updated: May 18, 2024