“ The normal doses of Melatonin ranges from 0.2 mg to 5 mg.
A dose of 0.5 mg may be all that is necessary to regulate the sleep cycle, and should be taken 3 to 5 hours before bed.
For people who want to take melatonin right before bed, a dose of 5 mg is appropriate, adding, "Some people report headache or stomach problems at higher doses, but these side effects are uncommon."