Jet lag is a sleep disorder that a person traveling experiences a sudden change in several time zones in a latitudinal direction (from east to west or west to east). Traveling east becomes more burdensome, because during a long trip takes shorter period of time day or night. The American Academy of Sleep Medicine defines jet lag as a team insomnia or excessive sleepiness syndrome, which occurs during the day after the trip after traveling at least two time zones. It may also include other symptoms such as gastrointestinal disorders immediately after the trip. The tourist feel general fatigue and loss of motivation, ability to concentrate, loss of interest. The sooner the circadian system adjusts to a new time zone, the shorter symptomatic period. A suitable method of preventing and treating sleep disorders after a fast changing time zones should be selected depending on the direction of flight and the planned length of stay in a different time zone.

Key words: jet lag, travelling, travel medicine.