According to the American Sleep Association, approximately 50 to 70 million US adults struggle with a sleep disorder. (2) Melatonin is perhaps best known as the “sleep hormone”, and melatonin supplements are commonly used to address conditions such as insomnia.

But did you know that there are a variety of other melatonin benefits? Melatonin is involved in regulating processes ranging from body temperature and bone mass to cyclical patterns of gene expression in reproduction. (5)(13)

Continue reading to learn more about melatonin benefits and considerations for melatonin supplementation.

What is melatonin?

5-methoxy-N-acetyltryptamine, commonly referred to as melatonin, is a hormone secreted by the pineal gland in the brain. Melatonin is synthesized from the amino acid tryptophan with the help of several enzymes. Tryptophan is metabolized into 5-hydroxytryptophan (5-HTP) and then serotonin, before being converted into melatonin. Melatonin is secreted by the pineal gland into the bloodstream and circulated in the body, eventually being metabolized primarily in the liver and excreted in urine. (5)(13)

Melatonin production and secretion relies on darkness and is inhibited by light (both daylight and artificial UV light). The retina of the eye transmits information about light exposure to the pineal gland. Melatonin secretion (release) follows a daily pattern that begins after sunset, peaks overnight between 2 am and 4 am, and gradually decreases during the rest of the night. Serum (blood) melatonin levels are generally low during the daylight hours. This pattern helps to regulate an individual’s daily sleep-wake cycle known as the circadian rhythm. (5)(13)

How does melatonin work?

Melatonin regulates various functions by interacting with molecular receptors throughout the body. Melatonin receptors are found on tissues, glands, and cells such as the:

  • Adipocytes (fat cells)
  • Adrenals
  • B and T lymphocytes (immune cells)
  • Brain
  • Breast
  • Gallbladder
  • Heart and arteries
  • Intestines
  • Kidney
  • Liver
  • Lung
  • Ovaries and uterus
  • Prostate
  • Skin (13)

What does melatonin do?

Melatonin, either endogenous (produced in the body) or exogenous (consumed through supplementation), acts as a regulator of various functions and processes in the body, including:

  • Body mass (13)
  • Body temperature (5)
  • Bone mass (13)
  • Circadian rhythm (e.g., sleep-wake rhythm) (5)(13)
  • Neurodevelopment (13)
  • Reproduction (13)
white bed with sheets, white flowers on a wooden bedside table

Melatonin is widely used to address sleep disorders, improve jet lag, and restore regular circadian rhythms.

Melatonin dysregulation

Light exposure from the sun and artificial sources is the primary factor affecting melatonin production and the body’s circadian rhythm. Exposure to light in the last few hours of typical sleep (prior to awakening) may shift the circadian rhythm earlier, known as advanced sleep-wake phase disorder. Conversely, light exposure in the evening and early hours of sleep can shift the circadian rhythm later, as seen in delayed sleep-wake phase disorder. Genetics and other factors also play a role in these sleep conditions, which are characterized by sleep timing being either advanced or delayed compared to the desired time. (5)

Melatonin dysfunction may occur when melatonin production or secretion is disrupted and/or when melatonin receptor function is impaired. In addition to light exposure, factors that may impair melatonin levels or signaling include:

  • Aging (15)
  • Alcohol intake
  • Caffeine intake
  • Certain medications (e.g., aspirin, benzodiazepines, chlorpromazine, ibuprofen)
  • Intense physical activity
  • Sleep timing (sleep and wake times) (5)

Certain health conditions have also been associated with dysregulated melatonin production, secretion, or signaling, including:

  • Alzheimer’s disease (15)
  • Autism spectrum disorder (13)
  • Cardiovascular disease (13)
  • Craniopharyngioma (non-cancerous brain tumor near the pituitary gland) (5)
  • Denervation (loss of nerve supply) due to pathology or trauma (e.g., spinal cord injury) (5)
  • Mental health conditions (e.g., bipolar disorder, major depressive disorder, schizophrenia) (13)

Melatonin benefits

Research has examined the therapeutic effects of melatonin supplementation in different health conditions outlined below.

Cardiometabolic diseases

Melatonin supplementation has been found to reduce blood pressure in individuals with hypertension. (13) Further, a trial in women with polycystic ovary syndrome (PCOS) found that melatonin supplementation improved insulin sensitivity, lipid profile, and sleep quality. (12)

Certain cancers

Melatonin exerts antioxidant and hormonal effects that may reduce the oxidative stress involved in carcinogenesis, the formation of cancer. In experimental and animal studies, melatonin has demonstrated oncostatic (cancer-halting) effects on tumors in breast, endometrial, ovarian, prostate, and intestinal tumors, which are also often sensitive to hormonal changes. (13)

Jet lag

Jet lag results from the body’s internal rhythms being out of sync with the day-night cycle, which often occurs following air travel over time zones. In a systematic review, melatonin was associated with preventing or reducing jet lag when supplementation was administered close to the desired bedtime at the location of travel. (10)

Neurodegenerative conditions

Experimental evidence suggests that melatonin may be beneficial for neurodegenerative conditions, such as Alzheimer’s disease, Huntington’s disease, and Parkinson’s disease. However, clinical trials are needed to assess the effects of melatonin supplementation on these conditions. (13)

Sleep disorders

Melatonin is an essential hormone involved in sleep timing. Two meta-analyses of controlled trials found that melatonin supplementation in individuals with sleep disorders was found to increase total sleep time, improve sleep quality, (8) reduce sleep onset time in insomnia, regulate sleep-wake patterns in blind individuals, and improve delayed sleep-wake phase disorder. (4)

Learn about our top sleep hygiene tips and supplements for improving sleep on the Fullscript blog.

person in bed holding a white alarm clock

When to take melatonin depends on many individual factors, including health goals.

Melatonin supplements

Melatonin supplements can be found in a range of different doses as either immediate-release or slow-release formulations. Melatonin is available in oral (e.g., capsules, tablets, chewables, dissolvables), intravenous, and dermal (e.g., skin patch) formats, and supplements are produced from animal, microbial, or synthetic sources. (11) A systematic review found that the bioavailability (proportion that is absorbed and available for use) of oral melatonin supplements ranges from 9 to 33%. (9)

We’ve answered some of the most commonly asked questions about melatonin supplementation below, however, if you’re a patient, we recommend speaking to your integrative healthcare practitioner, who can advise on how much melatonin to take and other considerations.

Melatonin dosage

A standard melatonin dosage hasn’t been established. The recommended melatonin dosage for adults ranges greatly, from doses as low as 0.3 mg for addressing sleep disorders to as high as 300 mg for certain neurodegenerative conditions. (5) Generally, melatonin dosage used in research ranges from approximately 0.5 to 5 mg per day. (5)(13)

When to take melatonin

When addressing sleep issues, it’s generally suggested to take melatonin about 45 minutes to an hour before bedtime. (9) Dose and timing may vary depending on individual needs and health goals.

How long does it take for melatonin to work?

Research has found that maximum plasma melatonin levels were reached in 45 minutes with oral immediate-release melatonin and two hours, 45 minutes with slow-release formulations. (9) It may take up to one to two weeks for desirable effects to occur. (14) Your practitioner can provide guidance for how long you should include melatonin in your wellness plan.

How long does melatonin last?

After an oral dose of 1 to 5 mg, melatonin remains in the body for several hours, with a return to baseline serum melatonin levels in four to eight hours. (13)

Is melatonin safe?

Melatonin is generally well-tolerated and safe for most individuals, even at high doses. (3) Reviews of clinical trials have found that few serious adverse effects have been experienced. (3)(6) When compared to a placebo, long-term melatonin supplementation was associated with only mild adverse effects. Clinical trials are lacking in certain populations, so melatonin may not be advised in certain individuals, such as pregnant or breastfeeding women. (3)

Melatonin side effects

Melatonin side effects that have been observed include agitation, fatigue/sleepiness, headache, mood swings, nausea, nightmares, skin irritation, and palpitations. (6)(11) Most of these adverse effects are temporary and resolve on their own or when melatonin treatment is discontinued. (6)

Is melatonin safe for kids?

While studies suggest melatonin supplements are safe for short-term use in children, more research is needed to determine the safety of long-term use. (7) Melatonin side effects that have been reported in children include abdominal pain, agitation, dizziness, drowsiness, feeling cold, headache, and increased bedwetting. (7)(11)

The bottom line

Given melatonin’s essential roles in sleep and regulating many body functions, it’s important to optimize your melatonin levels. Melatonin benefits have been seen in experimental or clinical trials of cardiometabolic conditions, certain cancers, jet lag, neurodegenerative conditions, and sleep disorders. If you’re a patient, speak with an integrative healthcare provider about supplementation and melatonin dosage.

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  1. Abdelgadir, I. S., Gordon, M. A., & Akobeng, A. K. (2018). Melatonin for the management of sleep problems in children with neurodevelopmental disorders: A systematic review and meta-analysis. Archives of Disease in Childhood, 103(12), 1155–1162.
  2. American Sleep Association. (2019, June 1). Sleep and sleep disorder statistics.
  3. Andersen, L. P., Gögenur, I., Rosenberg, J., & Reiter, R. J. (2016). The safety of melatonin in humans. Clinical Drug Investigation, 36(3), 169–175.
  4. Auld, F., Maschauer, E. L., Morrison, I., Skene, D. J., & Riha, R. L. (2017). Evidence for the efficacy of melatonin in the treatment of primary adult sleep disorders. Sleep Medicine Reviews, 34, 10–22.
  5. Aulinas, A. (2019). Physiology of the pineal gland and melatonin. In Endotext [Internet]., Inc.
  6. Besag, F. M. C., Vasey, M. J., Lao, K. S. J., & Wong, I. C. K. (2019). Adverse events associated with melatonin for the treatment of primary or secondary sleep disorders: A systematic review. CNS Drugs, 33(12), 1167–1186.
  7. Cummings, C., & Canadian Paediatric Society, Community Paediatrics Committee (2012). Melatonin for the management of sleep disorders in children and adolescents. Paediatrics & Child Health, 17(6), 331–336.
  8. Ferracioli-Oda, E., Qawasmi, A., & Bloch, M. H. (2013). Meta-analysis: melatonin for the treatment of primary sleep disorders. PloS one, 8(5), e63773.
  9. Harpsøe, N. G., Andersen, L. P. H., Gögenur, I., & Rosenberg, J. (2015). Clinical pharmacokinetics of melatonin: A systematic review. European Journal of Clinical Pharmacology, 71(8), 901–909.
  10. Herxheimer, A., & Petrie, K. J. (2002). Melatonin for the prevention and treatment of jet lag. Cochrane Database of Systematic Reviews, (2), CD001520.
  11. National Institutes of Health. (2019). Melatonin: What you need to know. National Center for Complementary and Integrative Health.
  12. Shabani, A., Foroozanfard, F., Kavossian, E., Aghadavod, E., Ostadmohammadi, V., Reiter, R. J., Eftekhar, T., & Asemi, Z. (2019). Effects of melatonin administration on mental health parameters, metabolic and genetic profiles in women with polycystic ovary syndrome: A randomized, double-blind, placebo-controlled trial. Journal of Affective Disorders, 250, 51–56.
  13. Tordjman, S., Chokron, S., Delorme, R., Charrier, A., Bellissant, E., Jaafari, N., & Fougerou, C. (2017). Melatonin: Pharmacology, functions and therapeutic benefits. Current Neuropharmacology, 15(3), 434–443.
  14. van Geijlswijk, I. M., van der Heijden, K. B., Egberts, A. C., Korzilius, H. P., & Smits, M. G. (2010). Dose finding of melatonin for chronic idiopathic childhood sleep onset insomnia: an RCT. Psychopharmacology, 212(3), 379–391.
  15. Wu, Y.-H., Zhou, J.-N., Van Heerikhuize, J., Jockers, R., & Swaab, D. F. (2007). Decreased MT1 melatonin receptor expression in the suprachiasmatic nucleus in aging and Alzheimer’s disease. Neurobiology of Aging, 28(8), 1239–1247.