Melatonin is a naturally occurring hormone that is produced by the pineal gland. This hormone is involved with sleep/wake cycles and can be useful when taken as a supplement for sleep disorders or jet lag. The presence of this hormone in the blood prepares the body for sleep; it decreases heart rate, body temperature, and decreases your level of alertness.
Taking Melatonin orally as a supplement can help someone get to sleep if they are having difficulty. A typical dose of this supplement is 5 mg. Melatonin taken on the day of arrival to induce sleep it can be effective on limiting the effects of jet lag.
It is important to consult a chiropractor or physician if you are considering a regimen of melatonin supplementation. They will help you determine if this is reasonable and help determine a dose that fits your needs.