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Drugs and Lactation Database (LactMed®) [Internet]. Bethesda (MD): National Institute of Child Health and Human Development; 2006-.

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Drugs and Lactation Database (LactMed®) [Internet].

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Last Revision: November 30, 2022.

Estimated reading time: 7 minutes

CASRN: 73-31-4

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Drug Levels and Effects

Summary of Use during Lactation

Melatonin is the hormone produced by the pineal gland that plays a role in regulating sleep and circadian rhythm as well as a possible role in gut-brain signaling.[1] It is a normal component of breastmilk, with concentrations higher during nighttime (peak around 3 am) than daytime.[2-5] Elective cesarean section results in higher daytime colostrum levels than with vaginal delivery.[6] Some authors suggest that mothers should nurse in the dark at night in order to avoid reductions in the melatonin content of breastmilk, which could disturb infant sleep patterns.[7] Differentiating milk pumped during the day from milk pumped during darkness has also been suggested for women pumping milk for their infants.[2,8] Some studies have attributed longer sleep time in breastfed infant than in formula-fed infants to melatonin in breastmilk.[9,10] Another study found higher colostrum melatonin levels at night which appeared to increase the phagocytic activity of colostral cells against bacteria.[11] A survey of 329 mothers found that infants who consumed mistimed expressed breastmilk took longer to get to sleep compared with infants who were directly breastfed, formula fed, fed timed expressed breast milk and fed breast milk/formula combined. Breastfed infants had more awakenings at night compared with infants who consumed mistimed expressed breastmilk.[12]

Exogenous administration of melatonin has no specific use during breastfeeding and no data exist on the safety of maternal use of melatonin during breastfeeding. However, doses higher than those expected in breastmilk after maternal supplementation have been used safely in infants.[13] It is unlikely that short-term use of usual doses of melatonin in the evening by a nursing mother would adversely affect her breastfed infant, although some authors recommend against its use in breastfeeding because of the lack of data and a relatively long half-life in preterm neonates.[14,15]

Dietary supplements do not require extensive pre-marketing approval from the U.S. Food and Drug Administration. Manufacturers are responsible to ensure the safety, but do not need to prove the safety and effectiveness of dietary supplements before they are marketed. Dietary supplements may contain multiple ingredients, and differences are often found between labeled and actual ingredients or their amounts. A manufacturer may contract with an independent organization to verify the quality of a product or its ingredients, but that does not certify the safety or effectiveness of a product. Because of the above issues, clinical testing results on one product may not be applicable to other products. More detailed information about dietary supplements is available elsewhere on the LactMed Web site.

The concentration of melatonin in breastmilk is unchanged after Holder pasteurization (62.5 degrees C for 30 minutes).[16]

Drug Levels

Melatonin is a normal component of human milk which is synthesized from the amino acid tryptophan.

Maternal Levels. Ten nursing mothers who were 3 to 5 days postpartum had serum and breastmilk melatonin levels measured between 2 pm and 5 pm and again between 2 am and 4 am. The breastmilk melatonin level averaged 23 ng/L at night, an average of 35% of the maternal serum concentration. Melatonin was undetectable (<10 ng/L) in milk during the daytime. Six of the mothers collected milk after each feeding for 24 hours once within 3 months of delivery. All mothers exhibited a marked circadian rhythm of melatonin excretion into breastmilk with detectable levels first occurring in the evening and dropping to undetectable levels in the morning.[17]

Twenty-one mothers collected breastmilk samples 5 times in a 24-hour period between day 5 and 10 postpartum. The median melatonin concentration in daytime milk (10 am to 10 pm) was 1.5 mg/L and the median concentration in nighttime milk (10 pm to 10 am) was 7.3 ng/L. No statistically significant difference was found between the breastmilk of mothers with preterm and fullterm infants.[2]

Twenty-four healthy mothers and 24 mothers with allergic eczema were studied in a crossover fashion to watch either a humorous video, a non-humorous video, or no video at 2-week intervals. Melatonin was measured in breastmilk 5 times between 10 pm and 6 am. Melatonin levels were higher at all times in the mothers who had watched the humorous video. The melatonin levels in mothers with eczema were generally lower than in normal mothers, but had a greater increase to similar levels in both groups after viewing the humorous video. The highest milk melatonin levels occurred at the 2 am sampling in all phases of the study, with a peak of 20.8 ng/L in healthy mothers and 19.9 ng/L in those with eczema.[18]

In studies in which exogenous oral melatonin was given to women, the resulting serum melatonin was variable, but peak serum concentrations ranged from 1.1 to 2.6 mcg/L for each 1 mg administered.[19-21] This would result in an average increase in breastmilk melatonin concentration from 0.4 to 1 mcg/L for each 1 mg administered to the mother, based on an average milk concentration of 35% of the maternal serum concentration. While the resulting concentrations would be higher than the typical physiologic peak milk concentrations of 0.02 mcg/L,[17,18] it would present a considerably lower dose to the infant than the 10 mg/kg dosages of melatonin that have been safely administered to neonates in clinical studies.[7,13]

One study found that breastmilk melatonin concentration was inversely correlated with breastmilk prolactin concentration and was higher in women experiencing fatigue in the morning.[22]

Five nursing mothers provided breastmilk samples every 2 hours over a 24-hour period. Melatonin was undetectable during the day, but began to rise at about 8 pm, reaching a peak at about 3 am, and then declining.[9]

Thirty women who were 48 to 72 hours postpartum provided 2 colostrum samples, one at noon and one at midnight. Melatonin levels in colostrum averaged about 16 ng/L at noon and 36 ng/L at midnight.[11]

A study in Turkey found that melatonin colostrum levels measured between 1:00 and 3:00 am between 48 and 72 hours postpartum were higher in mothers who delivered vaginally (mean 266 ng/L) than in those delivering by elective cesarean section (mean 205 ng/L) or emergency cesarean section (mean 167 ng/L). All differences between groups were statistically significant.[23]

Melatonin was analyzed in 392 breastmilk samples from 98 healthy nursing mothers at 0 to 30 days postpartum. Milk samples were obtained at 03:00, 09:00, 15:00, and 21:00 in one day. Peak milk levels occurred at 03:00 in both term and preterm milk. At 03:00 preterm colostrum had a higher average concentration than term colostrum 28.67 ng/L and 25.31 ng/L, respectively. Melatonin levels were numerically, but not statistically, higher in transitional and term milk at 03:00. The lowest levels of melatonin in milk occurred at 09:00 and 21:00.[4]

A study compared daytime and nighttime melatonin colostrum and milk levels in mothers who had an elective cesarean section (n=18) to mothers who had a vaginal delivery (n=21). Nighttime melatonin levels were higher in colostrum, transitional and mature milk in both groups, with nighttime melatonin ranging from 10.9 to 17.5 ng/L higher than daytime levels. Colostrum melatonin levels were higher in mothers who had an elective cesarean section (average 30.3 ng/L) than in mothers who had a vaginal delivery (average 14.7 ng/L).[6]

Infant Levels. A study of 8 breastfed and 6 formula-fed infants found different patterns of the melatonin metabolite, 6-sulfatoxymelatonin, in their urine. Breastfed infants had a sinusoidal excretion pattern with a peak at 6 am and a trough at 6 pm. Formula-fed infants had a simple increase in the metabolite that was at baseline between about 8 pm and 4 am with a peak at about noon.[24]

Effects in Breastfed Infants

A study on 54 exclusively breastfed infants (n = 54), formula-fed infants (n = 40) and their mothers questioned their mothers regarding infant behavior. Melatonin was measured in the milk of 5 of the mothers. Exclusively breastfed infants had a lower incidence of colic attacks, lower severity of irritability attacks, and a trend for longer nocturnal sleep duration. Melatonin in human milk showed a circadian curve and was unmeasurable in all artificial milks.[9]

An 18-month-old breastfed infant was having bleeding episodes since birth. A platelet aggregation test showed that the infant had reduced platelet aggregation after breastfeeding. When the infant was fasting, platelet aggregation was normal. The infant's mother was occasionally taking melatonin (dose not stated) for sleep. After she stopped melatonin intake for 3 months, the infant's platelet aggregation was normal and the infant had no further bleeding episodes.[25] The bleeding episodes were possibly caused by melatonin.

Effects on Lactation and Breastmilk

Relevant published information was not found as of the revision date.


Anderson G, Vaillancourt C, Maes M, et al. Breastfeeding and the gut-brain axis: Is there a role for melatonin? Biomol Concepts. 2017;8:185–95. [PubMed: 28723608]
Katzer D, Pauli L, Mueller A, et al. Melatonin concentrations and antioxidative capacity of human breast milk according to gestational age and the time of day. J Hum Lact. 2016;32:NP105–NP110. [PubMed: 27121237]
Molad M, Ashkenazi L, Gover A, et al. Melatonin stability in human milk. Breastfeed Med. 2019;14:680–2. [PubMed: 31381362]
Qin Y, Shi W, Zhuang J, et al. Variations in melatonin levels in preterm and term human breast milk during the first month after delivery. Sci Rep. 2019;9:17984. [PMC free article: PMC6884443] [PubMed: 31784629]
Italianer MF, Naninck EFG, Roelants JA, et al. Circadian cariation in human milk composition, a systematic review. Nutrients. 2020;12:E2328. [PMC free article: PMC7468880] [PubMed: 32759654]
Aparici-Gonzalo S, Carrasco-García Á, Gombert M, et al. Melatonin content of human milk: The effect of mode of delivery. Breastfeed Med. 2020;15:589–94. [PubMed: 32721174]
Sánchez-Barceló EJ, Mediavilla MD, Reiter RJ. Clinical uses of melatonin in pediatrics. Int J Pediatr. 2011;2011:892624. [PMC free article: PMC3133850] [PubMed: 21760817]
Arslanoglu S, Bertino E, Nicocia M, et al. WAPM Working Group on Nutrition: Potential chronobiotic role of human milk in sleep regulation. J Perinat Med. 2012;40:1–8. [PubMed: 22848905]
Cohen Engler A, Hadash A, Shehadeh N, et al. Breastfeeding may improve nocturnal sleep and reduce infantile colic: Potential role of breast milk melatonin. Eur J Pediatr. 2012;171:729–32. [PubMed: 22205210]
Rudzik AE, Robinson L, Ball HL. Infant sleep duration and melatonin levels in exclusively breastfed and exclusively formula fed infants. Am J Hum Biol 2016;28:294. [Abstract] P43. doi: 10.1002/ajhb.22831. [CrossRef]
Honorio-Franca AC, Hara CCP, Ormonde JV, et al. Human colostrum melatonin exhibits a day-night variation and modulates the activity of colostral phagocytes. J Appl Biomed. 2013;11:153–62. [CrossRef]
Booker LA, Spong J, Deacon-Crouch M, et al. Preliminary exploration into the impact of mistimed expressed breast milk feeding on infant sleep outcomes, compared to other feeding patterns. Breastfeed Med. 2022;17:853–8. [PubMed: 36137055]
Gitto E, Aversa S, Reiter RJ, et al. Update on the use of melatonin in pediatrics. J Pineal Res. 2011;50:21–8. [PubMed: 21029156]
Andersen LP, Gogenur I, Rosenberg J, et al. The safety of melatonin in humans. Clin Drug Investig. 2016;36:169–75. [PubMed: 26692007]
Vine T, Brown GM, Frey BN. Melatonin use during pregnancy and lactation: A scoping review of human studies. Braz J Psychiatry. 2022;44:342–8. [PMC free article: PMC9169489] [PubMed: 34730672]
Chrustek A, Sinkiewicz-Darol E, Lampka M, et al. Effect of pasteurization on melatonin concentration in human breast milk. Postepy Higieny I Medycyny Doswiadczalnej. 2022;76:220–7. [CrossRef]
Illnerová H, Buresova M, Presl J. Melatonin rhythm in human milk. J Clin Endocrinol Metab. 1993;77:838–41. [PubMed: 8370707]
Kimata H. Laughter elevates the levels of breast-milk melatonin. J Psychosom Res. 2007;62:699–702. [PubMed: 17540228]
DeMuro RL, Nafziger AN, Blask DE, et al. The absolute bioavailability of oral melatonin. J Clin Pharmacol. 2000;40:781–4. [PubMed: 10883420]
Fourtillan JB, Brisson AM, Gobin P, et al. Bioavailability of melatonin in humans after day-time administration of D(7) melatonin. Biopharm Drug Dispos. 2000;21:15–22. [PubMed: 11038434]
Markantonis SL, Tsakalozou E, Paraskeva A, et al. Melatonin pharmacokinetics in premenopausal and postmenopausal healthy female volunteers. J Clin Pharmacol. 2008;48:240–5. [PubMed: 18071190]
Groër M, Davis M, Casey K, et al. Neuroendocrine and immune relationships in postpartum fatigue. MCN Am J Matern Child Nurs. 2005;30:133–8. [PubMed: 15775810]
Namlı Kalem M, Kalem Z, Yuce T, et al. Comparison of melatonin levels in the colostrum between vaginal delivery and cesarean delivery. Am J Perinatol. 2018;35:481–5. [PubMed: 29166676]
Cubero J, Valero V, Sanchez J, et al. The circadian rhythm of tryptophan in breast milk affects the rhythms of 6-sulfatoxymelatonin and sleep in newborn. Neuro Endocrinol Lett. 2005;26:657–61. [PubMed: 16380706]
Luciani M, Massoud M, Foligno S, et al. Melatonin antiplatelets effect through breastfeeding: A sobering case. Haemophilia 2019;25 (SI; Suppl. 1):138-9. [Abstract]. doi: 10.1111/hae.13666. [CrossRef]

Substance Identification

Substance Name


CAS Registry Number


Drug Class

Breast Feeding


Milk, Human

Complementary Therapies

Central Nervous System Depressants


Disclaimer: Information presented in this database is not meant as a substitute for professional judgment. You should consult your healthcare provider for breastfeeding advice related to your particular situation. The U.S. government does not warrant or assume any liability or responsibility for the accuracy or completeness of the information on this Site.

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Attribution Statement: LactMed is a registered trademark of the U.S. Department of Health and Human Services.

Bookshelf ID: NBK501863PMID: 30000923


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