Supplements that can help you fall asleep include:
Magnesium. Magnesium helps activate the neurotransmitters responsible for sleep. Doses of 200–400 mg per day, taken with food, have been shown to improve sleep.
5 HTP (5-hydroxytryptophan). 5-HTP boosts the production of serotonin, which has been linked to the regulation of sleep. Doses of 300–500 mg per day, taken either once daily or in divided doses, seem to be effective in treating insomnia.
Melatonin. Melatonin is a hormone naturally produced by the body, but it can also be taken as a supplement to help regulate your sleep. Doses of 0.5–5 mg taken 30 minutes before bed seem to improve sleep quality.
Theanine. Theanine is an amino acid with sedative properties. Although it has not been shown to induce sleep, it could help with relaxation. Doses of 200 mg per day seem to be useful.
GABA (gamma-aminobutyric acid). GABA is a compound produced in the brain that inhibits certain transmitters and may help the central nervous system relax. Doses of 250–500 mg and no more than 1,000 mg are recommended.