Harvard Health Letter

When should you worry about fainting?

People who faint, or often feel like they’re going to faint, need medical attention. Fainting usually is caused by a temporary drop in blood pressure. Serious reasons for blood pressure to drop include internal bleeding, heart problems, and seizures. Less serious causes of fainting include stimulation of the vagus nerve, which can occur when straining while having a bowel movement (or, for men, passing urine), having blood drawn, getting an injection, hearing bad news, or even laughing too hard.
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