Melatonin is available in tablet form in the pharmacy area of major grocery stores without a prescription. I usually find it next to the natural vitamins and herbs. It’s inexpensive; I just bought a bottle of 120 3mg tablets at WalMart for $5.47. I noticed that the bottle says not for use by children less than 12 years of age. However, my pediatrician wrote out a “prescription” for my seven year old for me to keep at my house; Directing me to give her one 3mg tablet about an hour before bedtime. It has worked really well for my child and several of my friend’s children.

“Melatonin is a hormone made by a part of the brain called the pineal (say: "pin-ee-all") gland. Melatonin may help our bodies know when it's time to go to sleep and when it's time to wake up. Melatonin supplements (in pill form) can also be taken. There are two types of melatonin that may be used in these pills: natural and synthetic (man-made). Natural melatonin is made from the pineal gland of animals. This form could be contaminated with a virus and is not recommended. The synthetic form of melatonin does not have this risk. If you are not sure if your melatonin is natural or synthetic, ask your doctor or pharmacist before taking it.
Melatonin can be used to treat insomnia (difficulty falling asleep and/or staying asleep). It can also be taken to prevent jet lag. Beyond that, there is little scientific evidence that melatonin has a role in promoting health or treating disease.
Some people who have taken melatonin have reported sleepiness, headache, a "heavy-head" feeling, stomach discomfort, depression or feeling hungover. Further study is needed to find out more about melatonin's side effects, especially delayed or long-term effects. For example, we don't know if melatonin causes problems when taken with other medicines. We also don't know how melatonin may affect diseases.
Melatonin is sold without a prescription in health food stores and drug stores in the United States. However, melatonin products are not approved by the U.S. Food and Drug Administration. Since melatonin products are not regulated by a government agency, their purity, safety and effectiveness can't be assured.

Melatonin is a hormone produced in the brain by the pineal gland, from the amino acid tryptophan. The synthesis and release of melatonin are stimulated by darkness and suppressed by light, suggesting the involvement of melatonin in circadian rhythm and regulation of diverse body functions. Levels of melatonin in the blood are highest prior to bedtime.
Synthetic melatonin supplements have been used for a variety of medical conditions, most notably for disorders related to sleep.
Melatonin possesses antioxidant activity, and many of its proposed therapeutic or preventive uses are based on this property.
New drugs that block the effects of melatonin are in development, such as BMS-214778 or luzindole, and may have uses in various disorders.