晕厥（Fainting or Syncope）通常是指因突发性脑供血不足所导致的一过性意识丧失，美国国立医学图书馆认为，其主要诱因如下：

１、过度牵拉胃肠。

２、剧烈且时间较长的咳嗽。

３、原地不动站立时间过长。

４、由卧位变为直立位的过程太快。

５、极度疼痛或恐惧。

６、失血过多。

７、严重脱水。

８、血压突然降低。

９、饮酒过度或服用毒品或用药不当。

１０、过度换气。

１１、低血糖。

Health Tip: Risk Factors for Fainting

A temporary loss of consciousness

By Diana Kohnle

 (HealthDay News) -- Fainting occurs when you temporarily lose consciousness because of a sudden drop in blood flow to the brain. The U.S. National Library of Medicine mentions these possible causes of fainting:

１、Straining to produce a bowel movement.

２、Having a prolonged bout of coughing.

３、Standing in one spot for an extended period.

４、Standing up too quickly from lying down.

５、Having extreme pain or fear.

６、Bleeding heavily.

７、Suffering significant dehydration.

８、Having a rapid drop in blood pressure.

９、Taking certain medications, or abusing drugs or alcohol.

１０、Hyperventilating.

１１、Having low blood sugar.