Jet lag occurs when an individual’s biological clock is out of sync with local time. As a general rule it takes about a day for each hour of time zone change to recover from jet lag. Melatonin, available as a dietary supplement, is sometimes used to induce sleep when traveling. It is more useful when traveling east and may be taken before, during, or after traveling. It is best taken approximately five to seven hours before the usual bedtime in the old time zone. Travelers should consult their physicians before using melatonin. It is not recommended for pregnant or breast-feeding women and children.