Melatonin, Serum/Plasma

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The following is a list of what is included in the item above. Click the test(s) below to view what biomarkers are measured along with an explanation of what the biomarker is measuring.


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The Melatonin, Serum/Plasma test contains 1 test with 1 biomarker.

Melatonin, Serum/Plasma Test Description

Test Name:
Melatonin, Serum/Plasma

This test measures the level of melatonin in the serum or plasma. Melatonin is a hormone produced by the pineal gland in response to darkness, playing a crucial role in regulating the body's circadian rhythm, sleep patterns, and some other physiological functions.

Clinical Utility:

  1. Sleep Disorders: Evaluating sleep disorders and disturbances, especially in individuals with suspected circadian rhythm disorders such as delayed sleep phase syndrome (DSPS) or advanced sleep phase syndrome (ASPS).
  2. Jet Lag Assessment: Understanding the severity and providing management guidelines for individuals frequently traveling across time zones.
  3. Work Shift Disorders: Diagnosing and treating those with sleep problems related to rotating or night shift work.
  4. Effect of Blindness: People who are blind may have sleep problems because the lack of light input disrupts their circadian rhythm.
  5. Pineal Tumors: Monitoring and diagnosing pineal tumors, which can affect melatonin production.
  6. Evaluation of Seasonal Affective Disorder (SAD): Some people with SAD may produce melatonin at the wrong times of day.


  1. Sample Collection: Blood is drawn from a vein, typically in the arm.
  2. Processing: The blood sample is allowed to clot and then centrifuged to separate the clear liquid (serum/plasma) from the cells.
  3. Measurement: The level of melatonin is measured using specialized laboratory techniques such as radioimmunoassay (RIA) or enzyme-linked immunosorbent assay (ELISA).


  • Patients may be required to maintain a specific sleep-wake cycle before the test.
  • Avoid caffeine, alcohol, and certain medications that can affect melatonin levels.
  • Test timings might vary; sometimes, multiple samples may be collected over a 24-hour period to observe melatonin production patterns.

Reference Range(s)
Melatonin levels typically show a circadian rhythm, with levels being lowest during daylight hours and peaking during the night. The exact reference ranges might vary based on the lab, method of analysis, and the patient's age.

Day time 2.0-80.0 pg/mL
Night time 18.5-180.0 pg/mL

Alternative Name(s)

Sleep hormone,N-acetyl-5-methoxy-tryptamine


  • Increased Levels: May be seen in individuals with certain sleep disorders, some cases of depression, or due to environmental factors affecting the sleep-wake cycle.
  • Decreased Levels: Can be associated with insomnia, certain medications, exposure to light during nighttime, and some medical conditions like pineal tumors.


  • Medications, caffeine, and alcohol can affect results.
  • The test does not provide a direct diagnosis but offers a piece of the puzzle for the clinician.

Always consult with a healthcare provider for interpretation of lab results. The interpretation of the melatonin level in the serum/plasma should be combined with clinical findings, patient history, and other diagnostic tests.

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