Generally, people do not need a medical evaluation for a diagnosis of jet lag. If you have traveled across several time zones and feel the symptoms associated with jet lag, you likely have it.

How long does it take to recover from jet lag?
Recovering from jet lag depends on the number of time zones crossed while traveling. In general, the body will adjust to the new time zone at the rate of one or two time zones per day. For example, if you crossed six time zones, the body will typically adjust to this time change in three to five days.

Jet lag is temporary, so the prognosis is excellent and most people will recover within a few days.

Complications of jet lag are extremely rare. If a person has a preexisting heart condition, the stress of the disruption in the circadian rhythm, combined with the stress of travel, the high altitude, and immobility during flight may result in a heart attack. If the jet lag results in chronic sleep deprivation, stroke may occur in certain predisposed individuals.

What is a time zone?
The definition of a time zone is a geographical region which has the same time everywhere within it. The world has 24 time zones, one for each hour in the day. Each zone runs from north to south in strips that are approximately 1,000 miles (1,600 kilometers) wide. (The actual width of each zone varies to accommodate political and geographical boundaries.) As the earth rotates, dawn occurs at a set hour in one time zone, then an hour later in the time zone immediately to the west and so on through the 24-hour cycle.

What causes jet lag?
The cause of jet lag is the inability of the body of a traveler to immediately adjust to the time in a different zone. Thus, when a New Yorker arrives in Paris at midnight Paris time, his or her body continues to operate on New York time. As the body struggles to cope with the new schedule, temporary insomnia, fatigue, irritability, and an impaired ability to concentrate may set in. The changed bathroom schedule may cause constipation or diarrhea, and the brain may become confused and disoriented as it attempts to juggle schedules.