Melatonin
Also known as: N-Acetyl-5-Methoxytryptamine
What Does Melatonin Measure?
Melatonin is a hormone produced primarily by the pineal gland in the brain that is measured in blood, urine, or saliva samples. Blood and saliva tests typically capture the level of circulating melatonin at a specific point in time, while urine tests measure a metabolite called 6-sulfatoxymelatonin (6-SMT) to reflect overall melatonin production over several hours. Because melatonin levels fluctuate dramatically throughout the day and night—rising sharply in darkness and falling in light—testing is usually done at specific time points, most commonly at night or across multiple samples to map the full secretion pattern.
Why Does Melatonin Matter?
Melatonin is the body's primary timekeeper, regulating the sleep-wake cycle (circadian rhythm) and signaling to virtually every organ system that it is time to rest and repair. Abnormal melatonin levels are associated with insomnia, shift-work disorder, jet lag, seasonal affective disorder (SAD), depression, and certain neurological conditions. Beyond sleep, melatonin has potent antioxidant and anti-inflammatory properties, plays a role in immune function, reproductive hormone regulation, and has been studied in the context of cancer biology and metabolic health. Assessing melatonin helps clinicians diagnose circadian rhythm disorders, guide light therapy or supplementation, and understand underlying hormonal imbalances affecting sleep and overall well-being.
Normal Ranges
Males
Nighttime peak (2–4 AM): 80–200 pg/mL (serum); Daytime trough: <10 pg/mL; Urinary 6-SMT: 10–80 µg/8-hour overnight collection
Females
Nighttime peak (2–4 AM): 80–200 pg/mL (serum); Daytime trough: <10 pg/mL; Urinary 6-SMT: 10–80 µg/8-hour overnight collection
Children
Higher than adults during prepubertal years (up to 325 pg/mL at night); declines significantly at puberty; varies substantially by age
Causes of High Levels
- Darkness exposure and absence of artificial light at night (physiologically normal nighttime rise)
- Supplemental melatonin use or overdose leading to supraphysiological levels
- Pineal gland tumors (pinealomas) causing excess secretion
- Certain antidepressants (e.g., fluvoxamine) that inhibit melatonin-metabolizing enzymes (CYP1A2)
- Hypogonadism or delayed puberty, which is associated with elevated melatonin in some cases
- Extreme cold exposure or prolonged darkness in winter months (seasonal variation)
Causes of Low Levels
- Aging, as melatonin production naturally declines significantly after age 40–50
- Excessive exposure to artificial blue light at night (from screens, LED lighting) suppressing pineal secretion
- Night-shift work disrupting the normal dark-phase signal for melatonin release
How to Improve Your Melatonin
Diet
- Eat melatonin-containing foods in the evening such as tart cherries, walnuts, grapes, and tomatoes to support nighttime levels
- Include tryptophan-rich foods (turkey, eggs, dairy, pumpkin seeds) as tryptophan is the precursor to serotonin and then melatonin
- Consume foods rich in vitamin B6 (chickpeas, salmon, potatoes) which is a cofactor in melatonin synthesis
- Eat magnesium-rich foods (dark leafy greens, nuts, seeds) as magnesium supports GABA activity and melatonin regulation
- Avoid caffeine and alcohol in the evening, as both suppress melatonin secretion and fragment sleep architecture
Supplements
- Melatonin 0.5–3 mg taken 30–60 minutes before desired sleep onset for insomnia or jet lag (low doses are often as effective as high doses)
- Magnesium glycinate 200–400 mg at night to support sleep quality and complement melatonin production
- L-tryptophan 500–1000 mg or 5-HTP 50–100 mg in the evening to boost the melatonin precursor pathway (consult a physician before use)
- Vitamin B6 (pyridoxal-5-phosphate) 10–25 mg to support the enzymatic conversion of serotonin to melatonin
Related Biomarkers
Frequently Asked Questions
What is the best time to test melatonin levels?
Because melatonin levels change dramatically throughout the day, timing is critical. Blood or saliva testing is ideally done between 2 AM and 4 AM when levels peak, or as a dim-light melatonin onset (DLMO) test taken hourly in the evening under controlled lighting conditions. Urine tests measuring the metabolite 6-sulfatoxymelatonin (6-SMT) are collected overnight and are convenient alternatives that reflect total nighttime production. A single daytime blood draw is generally not useful for diagnosing melatonin deficiency.
Can melatonin supplements raise my levels if they are low?
Yes, melatonin supplements can raise circulating levels, but more is not always better. Low doses of 0.5–1 mg are often sufficient and can be as effective as higher doses (5–10 mg), which may cause next-day grogginess or excessive sedation. Supplemental melatonin works best when timed correctly—typically 30 to 60 minutes before the desired sleep onset. It is most evidence-based for circadian rhythm disorders like jet lag and delayed sleep phase syndrome rather than chronic primary insomnia.
Does melatonin decline with age, and should older adults take supplements?
Yes, melatonin production declines significantly with aging due to calcification of the pineal gland and reduced enzyme activity. Many adults over 60 produce only a fraction of the melatonin they did in youth, which contributes to sleep disturbances common in older age. Low-dose melatonin supplementation (0.5–2 mg) is generally considered safe for older adults and may improve sleep quality, though it is wise to consult a healthcare provider to rule out underlying causes and check for medication interactions.