What is jet lag?

Your body has an internal clock called circadian rhythm. Circadian rhythm regulates your temperature, blood pressure, and hormones. When you travel across several time zones in one day, your internal clock gets out of step with the time at your destination. This is called jet lag.

Who is likely to get jet lag?

The more time zones you cross in one day, the more likely you are to get jet lag. Jet lag is common after crossing five time zones. It usually is worse when you travel in an eastern direction. The symptoms might also be worse in older people.

What are the symptoms of jet lag?

Jet lag includes a number of symptoms. After eastward flights, you might have trouble falling asleep at the new bedtime. After westward flights, you might wake up too early in the morning. These sleep problems can cause fatigue, irritability, difficulty concentrating, clumsiness, memory problems, and weakness.

Other symptoms of jet lag include headache, loss of appetite, and upset stomach. These symptoms are usually worse for the first two days after arrival, and then they get better.

What can I do to prevent and treat jet lag?

General recommendations:

• Get enough rest before you start traveling.

• Because the air in airplanes is dry, drink lots of nonalcoholic, decaffeinated beverages and water, so you won't get dehydrated.

Specific recommendations to help your internal clock adjust to the new time (if you will be staying more than a few days):

• Adjust your daily routine to the new time schedule as soon as possible. This includes meals and other activities, as well as sleep. You can even start your new routine just before you leave on your trip.

• Get outdoors in natural light as much as possible after your arrival.

• If you do not have epilepsy or take medicine to prevent blood clotting, you can take a dietary supplement called melatonin when you get to your destination. Some studies show that taking small doses (5 mg or less) of melatonin at bedtime can help with jet lag. Keep in mind that because melatonin is not considered a drug, its quality is not monitored by the U.S. Food and Drug Administration.

Even if you follow this advice, you still might get jet lag. Try to plan your schedule so that you do not have to do too much on the first two days after you arrive.