Melatonin Levels

Melatonin levels in the body are the measurable concentration of the hormone melatonin — primarily produced by the pineal gland — circulating in the bloodstream or saliva to regulate the sleep-wake cycle. In healthy diurnal organisms, these levels follow a distinct circadian rhythm, characterized by extremely low concentrations during daylight hours and a sharp increase after the onset of darkness, known as dim light melatonin onset (DLMO). Maintaining appropriate melatonin levels is critical for stabilizing the internal clock; disruptions, such as the delayed or flattened secretion often seen in bipolar disorder (BD) or aging, can lead to persistent insomnia, daytime fatigue, and broader metabolic or mood dysregulation.