Determining melatonin levels can be a critical tool for accurately diagnosing endocrine dysfunctions, effectively treating mood and sleep disorders, and revealing contributing factors in the pathology of various diseases. Melatonin has a pivotal role in regulating body temperature, the sleep-wake cycle, female reproductive hormones, and cardiovascular function. It can also serve as a chronobiological indicator of the aging process because of its important antioxidant contributions. Melatonin is the major modulator of annual and daily biorhythms in the body. With its unique ability to pass through all blood barriers in the body, melatonin acts as the central hub of physiological function, orchestrating the complex interactions between mind, body and the environment.

Melatonin's diurnal rhythm is synchronized by the light-dark cycle and is strongly affected by day length, artificial illumination, electromagnetic energy, exercise and other factors. Secretion levels peak in childhood and diminish over an individual's lifespan. Since melatonin exhibits strong regenerative and integrative influences over the body, gradual decreases may explain the age-dependent weakening of immune function.

An increasing number of laboratories offer saliva testing as a convenient way to check melatonin status. See our links page for some such labs.