Last update Aug. 31, 2020

Magnesium Sulfate


Safe substance and/or breastfeeding is the best option.

Magnesium sulphate taken intravenously is used to treat certain arrythmias, eclampsia and convulsions of newborns and infants, orally as an osmotic laxative and in the prophylaxis of migraine (Pringsheim 2012) and, topically, for certain types of skin inflammation.

Daily magnesium requirements for breastfeeding mothers are estimated at 310 to 360 mg (MedlinePlus 2017); some countries have established figures of up to 450 mg daily (Hall 2010).

Since the last update we have not found any published data on its excretion in breast milk.
Magnesium is a natural component of milk. The average natural concentration of magnesium in milk is 31 mg/L (15 to 64 mg/L) (Dórea 2000, Feeley 1983).

Ingested magnesium is not concentrated in breastmilk. Its concentration in milk is very stable and depends little on diet (USD 2000) and other factors, including intravenous administration of magnesium sulphate to the mother: the levels of magnesium in milk of mothers treated with intravenous magnesium sulphate were 6.4 mg/L versus 4.8 mg/L in untreated patients (Cruikshank 1982, Dorea 2000), a clinically non-significant difference for the infant, which also disappeared within a few hours.

Its low oral bioavailability hinders transfer to plasma and, therefore, to breastmilk, as well as transfer to infant plasma via breastmilk (Morris 1987).

In women treated with magnesium sulphate before or during childbirth, there has been a delay in the stimulation of milk production or lactogenesis II (Haldeman 1993) and less frequency of breastfeeding (Meier 2005) as well as hypotonia in newborns (Riaz 1998, Rasch 1982), which could interfere with adequate breast stimulation, but this can be counteracted by a firm decision by the mother and effective support for her (Cordero 2012).

Various medical associations and expert consensus consider the use of various magnesium salts to be safe during breastfeeding (Hale 2019, Briggs 2015, Dennis 2012, Schaefer 2007, Mahadevan 2006, Richter 2005, Nice 2000, Broussard 1998, Idama 1998).
American Academy of Pediatrics: medication usually compatible with breastfeeding (AAP 2001).
List of WHO essential medicines: compatible with breastfeeding (WHO / UNICEF 2002).

If the intravenous administration of magnesium sulphate is considered compatible with breastfeeding, all the more reason that salts administered orally will also be compatible (Hagemann 1998).


We do not have alternatives for Magnesium Sulfate since it is relatively safe.

Suggestions made at e-lactancia are done by APILAM team of health professionals, and are based on updated scientific publications. It is not intended to replace the relationship you have with your doctor but to compound it. The pharmaceutical industry contraindicates breastfeeding, mistakenly and without scientific reasons, in most of the drug data sheets.

Jose Maria Paricio, Founder & President of APILAM/e-Lactancia

Your contribution is essential for this service to continue to exist. We need the generosity of people like you who believe in the benefits of breastfeeding.

Thank you for helping to protect and promote breastfeeding.

José María Paricio, founder of e-lactancia.

Other names

Magnesium Sulfate is also known as

Magnesium Sulfate in other languages or writings:


Main tradenames from several countries containing Magnesium Sulfate in its composition:


Variable Value Unit
Oral Bioavail. 4 - 15 %
Molecular weight 120 - 247 daltons
Protein Binding 25 - 40 %
Tmax 0.01 hours
3 - 4 hours
M/P ratio 2 -
Theoretical Dose 4.6 mg/Kg/d
Relative Dose 0.2 %


  1. Hale TW. Medications & Mothers' Milk. 1991- . Springer Publishing Company. Available from Consulted on April 10, 2024 Full text (link to original source)
  2. MedlinePlus. Magnesium in diet. Medical Encyclopedia 2017 Full text (link to original source) Full text (in our servers)
  3. MedlinePlus. Magnesio en la dieta. Enciclopedia médica. 2017 Full text (link to original source) Full text (in our servers)
  4. Cordero L, Valentine CJ, Samuels P, Giannone PJ, Nankervis CA. Breastfeeding in women with severe preeclampsia. Breastfeed Med. 2012 Abstract
  5. Pringsheim T, Davenport W, Mackie G, Worthington I, Aubé M, Christie SN, Gladstone J, Becker WJ; Canadian Headache Society Prophylactic Guidelines Development Group. Canadian Headache Society guideline for migraine prophylaxis. Can J Neurol Sci. 2012 Abstract Full text (in our servers)
  6. Dennis AT. Management of pre-eclampsia: issues for anaesthetists. Anaesthesia. 2012 Sep;67(9):1009-20. Abstract Full text (link to original source) Full text (in our servers)
  7. Hall Moran V, Lowe N, Crossland N, Berti C, Cetin I, Hermoso M, Koletzko B, Dykes F. Nutritional requirements during lactation. Towards European alignment of reference values: the EURRECA network. Matern Child Nutr. 2010 Oct;6 Suppl 2:39-54. Abstract Full text (link to original source) Full text (in our servers)
  8. Schaefer C, Peters P, Miller RK. Drugs During Pregnancy and Lactation. Treatment options and risk assessment. Elsevier, second edition. London. 2007
  9. EFSA. European Food Safety Authority. Tolerable upper intake levels for vitamins and minerals. Scientific Committee on Food. 2006 Full text (link to original source) Full text (in our servers)
  10. Mahadevan U, Kane S. American gastroenterological association institute technical review on the use of gastrointestinal medications in pregnancy. Gastroenterology. 2006 Jul;131(1):283-311. Review. Abstract Full text (link to original source) Full text (in our servers)
  11. Meier B, Huch R, Zimmermann R, von Mandach U. Does continuing oral magnesium supplementation until delivery affect labor and puerperium outcome? Eur J Obstet Gynecol Reprod Biol. 2005 Dec 1;123(2):157-61. Abstract
  12. Richter JE. Review article: the management of heartburn in pregnancy. Aliment Pharmacol Ther. 2005 Nov 1;22(9):749-57. Review. Abstract Full text (in our servers)
  13. WHO / UNICEF. BREASTFEEDING AND MATERNAL MEDICATION Recommendations for Drugs in the Eleventh WHO Model List of Essential Drugs. Department of Child and Adolescent Health and Development (WHO/UNICEF) 2002 Abstract Full text (link to original source) Full text (in our servers)
  14. AAP - American Academy of Pediatrics Committee on Drugs. Transfer of drugs and other chemicals into human milk. Pediatrics. 2001 Sep;108(3):776-89. Abstract Full text (link to original source) Full text (in our servers)
  15. Dórea JG. Magnesium in human milk. J Am Coll Nutr. 2000 Apr;19(2):210-9. Review. Abstract
  16. Nice FJ, Snyder JL, Kotansky BC. Breastfeeding and over-the-counter medications. J Hum Lact. 2000 Nov;16(4):319-31. Review. Erratum in: J Hum Lact 2001 Feb;17(1):90. Abstract
  17. Riaz M, Porat R, Brodsky NL, Hurt H. The effects of maternal magnesium sulfate treatment on newborns: a prospective controlled study. J Perinatol. 1998 Abstract
  18. Broussard CN, Richter JE. Treating gastro-oesophageal reflux disease during pregnancy and lactation: what are the safest therapy options? Drug Saf. 1998 Oct;19(4):325-37. Review. Abstract
  19. Idama TO, Lindow SW. Magnesium sulphate: a review of clinical pharmacology applied to obstetrics. Br J Obstet Gynaecol. 1998 Mar;105(3):260-8. Review. No abstract available. Abstract
  20. Hagemann TM. Gastrointestinal medications and breastfeeding. J Hum Lact. 1998 Sep;14(3):259-62. Review. Abstract
  21. Haldeman W. Can magnesium sulfate therapy impact lactogenesis? J Hum Lact. 1993 Abstract
  22. Morris ME, LeRoy S, Sutton SC. Absorption of magnesium from orally administered magnesium sulfate in man. J Toxicol Clin Toxicol. 1987;25(5):371-82. Abstract
  23. Feeley RM, Eitenmiller RR, Jones JB Jr, Barnhart H. Calcium, phosphorus, and magnesium contents of human milk during early lactation. J Pediatr Gastroenterol Nutr. 1983 May;2(2):262-7. Abstract
  24. Cruikshank DP, Varner MW, Pitkin RM. Breast milk magnesium and calcium concentrations following magnesium sulfate treatment. Am J Obstet Gynecol. 1982 Jul 15;143(6):685-8. No abstract available. Abstract
  25. Rasch DK, Huber PA, Richardson CJ, L'Hommedieu CS, Nelson TE, Reddi R. Neurobehavioral effects of neonatal hypermagnesemia. J Pediatr. 1982 Feb;100(2):272-6. Abstract

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