Melatonin SRT™ provides 6 mg of the hormone melatonin in a sustained release tablet. As a supplement, melatonin is useful for regulating sleep and the body’s daily rhythmic cycle.* Various factors may cause melatonin levels to become low, such as inadequate dietary intake of its precursor tryptophan, low levels of serotonin, normal aging, insufficient exposure to natural light, and certain medications. Due to melatonin’s relatively short half-life in the body, a sustained release formula may be more suitable for those who experience difficulty staying asleep through the night.