Fainting is medically called syncope "sing-ka-pee" is a sudden and temporary loss of consciousness that occurs as a result of a lack of sufficient blood flow to the brain. There are a number of things that can  cause this to happen, including a sudden drop in blood pressure, anemia, an irregular heartbeat, seizures, extreme heat, hyperventilation, hunger, and hypoglycemia.  Standing for a long time in a hot, stuffy room, exhaustion, emotional upset, fear, or fever may also cause a person to faint. People who have  cardiovascular problems and those who take certain  drugs may be more prone to fainting than the  average person. Before fainting, you may experience dizziness, weakness, nausea, sweating, blurred vision, and/or a feeling of numbness in your hands or feet; you may suddenly turn pale and your skin may feel  cold. Upon awakening, you may feel tired and develop a headache. If you lose consciousness apparently due to one of the factors listed above, and make a complete  recovery within 15 minutes, it is likely that  you have experienced a fainting episode. A person who has fainted will usually awaken fairly readily,  especially if smelling salts are used, and will be aware and oriented upon awakening. If you regain consciousness with difficulty and are disoriented, you  may have a more serious problem.