Sure, fainting in films can provide comic relief, but in real life, it’s no laughing matter. Syncope, the medical term for temporarily losing consciousness, occurs when there’s a drop in blood flow to the brain.

About one third of people faint at some point in their lives. While fainting spells among young people who don’t have severe heart conditions are usually situational, Jose Dizon, MD, cardiologist and associate professor of medicine at Columbia University, explains that for people older than 50 it can indicate an underlying health problem, such as heart disease or stroke. “The most severe situations have to do with the heart rhythm,” Dizon says. “Either the heartbeat is too slow or too fast, in which case the heart doesn’t pump enough blood effectively.”

Dizon recommends paying close attention to your body. Look for the warning signs, such as feeling sweaty and nauseous, that precede a fainting spell. He also suggests knowing and limiting your triggers. For example, severe dehydration can cause a sudden drop in blood pressure, so drink lots of water.