Last update March 4, 2022

Metformin Hydrochloride

Very Low Risk

Safe. Compatible. Minimal risk for breastfeeding and infant.

Oral antidiabetic biguanide medication used for treatment of Diabetes Type II, Obesity and Polycystic Ovarian Syndrome (PCOS). Oral administration one to three times daily. Biguanide drugs act by decreasing Neoglycogenesis (new formation of sugar) in the liver. Metformin does not cause hypoglycaemia. (Dashora 2022 y 2018).

Metformin is excreted into breast milk in non-significant amount. (Eyal 2010, Gardiner 2008, Briggs 2005, Hale 2004, Gardiner 2003, Hale 2002)

No problems have been observed in infants whose mothers have taken it. (Glueck 2007 & 2006, Briggs 2005, Hale 2004 & 2002, Gardiner 2003)

Plasma levels in infants were very low or undetectable. (Hale 2004 & 2002, Gardiner 2003)

Evidence for its efficacy as a galactogogue is insufficient. (Grzeskowiak 2019, Nommsen 2019))

Several medical societies, experts and expert consensus, consider the use of this medication to be safe during breastfeeding. (Philips 2021, Dashora 2018, Anderson 2018, Priya 2018, Serrano 2015, Rowe 2013, Refuerzo 2011, Amir 2011, Glatstein 2009, Feig 2007, Glueck 2006, Nice 2004)

Obesity is associated with breastfeeding difficulties. In spite of Metformin has beneficial effect on Obesity, this is not true with PCOS because lactation capacity is related to growth of breast tissue during pregnancy which is not improved by the use of Metformin. (Vanky 2012)

Oral antidiabetic drugs are not effective for Diabetes Type I. For Diabetes Type II diet, physical exercise and breastfeeding may ameliorate glycemia levels.

See below the information of this related product:


  • Hypocaloric Diet ( Safe. Compatible. Minimal risk for breastfeeding and infant.)
  • Maternal Sport ( Safe. Compatible. Minimal risk for breastfeeding and infant.)

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

Metformin Hydrochloride in other languages or writings:


Metformin Hydrochloride belongs to this group or family:


Main tradenames from several countries containing Metformin Hydrochloride in its composition:


Variable Value Unit
Oral Bioavail. 50 - 60 %
Molecular weight 166 daltons
Protein Binding 0 %
VD 0.9 - 3.9 l/Kg
pKa 12.3 -
Tmax 2.5 hours
6.5 hours
M/P ratio 0.4 - 0.6 -
Theoretical Dose 0.02 - 0.06 mg/Kg/d
Relative Dose 0.11 - 0.65 %


  1. Dashora U, Levy N, Dhatariya K, Willer N, Castro E, Murphy HR; Joint British Diabetes Societies In Patient group.. Managing hyperglycaemia during antenatal steroid administration, labour and birth in pregnant women with diabetes - an updated guideline from the Joint British Diabetes Society for Inpatient Care. Diabet Med. 2022 Feb;39(2):e14744. Abstract
  2. Philips JC, Oriot P, Renson V, Vandelaer A, Grandfils S. [Gestational diabetes mellitus : what after delivery ?] Rev Med Suisse. 2021 Aug 25;17(747):1386-1390. French. Abstract
  3. Grzeskowiak LE, Wlodek ME, Geddes DT. What Evidence Do We Have for Pharmaceutical Galactagogues in the Treatment of Lactation Insufficiency?-A Narrative Review. Nutrients. 2019 Apr 28;11(5). pii: E974. Abstract Full text (link to original source)
  4. Nommsen-Rivers L, Thompson A, Riddle S, Ward L, Wagner E, King E. Feasibility and Acceptability of Metformin to Augment Low Milk Supply: A Pilot Randomized Controlled Trial. J Hum Lact. 2019 May;35(2):261-271. Abstract
  5. Dashora U, Murphy HR, Temple RC, Stanley KP, Castro E, George S, Dhatariya K, Haq M, Sampson M; Joint British Diabetes Societies (JBDS) for Inpatient Care.. Managing hyperglycaemia during antenatal steroid administration, labour and birth in pregnant women with diabetes. Diabet Med. 2018 Aug;35(8):1005-1010. Abstract
  6. Priya G, Kalra S. Metformin in the management of diabetes during pregnancy and lactation. Drugs Context. 2018 Jun 15;7:212523. Abstract
  7. Anderson PO. Treating Diabetes During Breastfeeding. Breastfeed Med. 2018 May;13(4):237-239. Abstract
  8. Serrano Aguayo P, García de Quirós Muñoz JM, Bretón Lesmes I, Cózar León MV. Tratamiento de enfermedades endocrinológicas durante la lactancia. [Endocrinologic diseases management during breastfeeding.] Med Clin (Barc). 2015 Jan 20;144(2):73-9. Abstract
  9. Rowe H, Baker T, Hale TW. Maternal medication, drug use, and breastfeeding. Pediatr Clin North Am. 2013 Feb;60(1):275-94. Abstract
  10. Vanky E, Nordskar JJ, Leithe H, Hjorth-Hansen AK, Martinussen M, Carlsen SM. Breast size increment during pregnancy and breastfeeding in mothers with polycystic ovary syndrome: a follow-up study of a randomised controlled trial on metformin versus placebo. BJOG. 2012 Abstract Full text (link to original source) Full text (in our servers)
  11. Refuerzo JS. Oral hypoglycemic agents in pregnancy. Obstet Gynecol Clin North Am. 2011 Abstract
  12. Amir LH, Pirotta MV, Raval M. Breastfeeding--evidence based guidelines for the use of medicines. Aust Fam Physician. 2011 Sep;40(9):684-90. Review. Abstract Full text (link to original source) Full text (in our servers)
  13. Eyal S, Easterling TR, Carr D, Umans JG, Miodovnik M, Hankins GD, Clark SM, Risler L, Wang J, Kelly EJ, Shen DD, Hebert MF. Pharmacokinetics of metformin during pregnancy. Drug Metab Dispos. 2010 Abstract Full text (link to original source) Full text (in our servers)
  14. Glatstein MM, Djokanovic N, Garcia-Bournissen F, Finkelstein Y, Koren G. Use of hypoglycemic drugs during lactation. Can Fam Physician. 2009 Abstract Full text (link to original source) Full text (in our servers)
  15. Gardiner SJ, Kirkpatrick CM, Zhang M, Begg EJ. Cimetidine does not appear to influence the distribution of metformin into human milk. Br J Clin Pharmacol. 2008 Abstract Full text (link to original source) Full text (in our servers)
  16. Glueck CJ, Wang P. Metformin before and during pregnancy and lactation in polycystic ovary syndrome. Expert Opin Drug Saf. 2007 Abstract
  17. Feig DS, Briggs GG, Koren G. Oral antidiabetic agents in pregnancy and lactation: a paradigm shift? Ann Pharmacother. 2007 Abstract
  18. Thatcher SS, Jackson EM. Pregnancy outcome in infertile patients with polycystic ovary syndrome who were treated with metformin. Fertil Steril. 2006 Abstract
  19. Glueck CJ, Salehi M, Sieve L, Wang P. Growth, motor, and social development in breast- and formula-fed infants of metformin-treated women with polycystic ovary syndrome. J Pediatr. 2006 Abstract
  20. Briggs GG, Ambrose PJ, Nageotte MP, Padilla G, Wan S. Excretion of metformin into breast milk and the effect on nursing infants. Obstet Gynecol. 2005 Abstract
  21. Nice FJ, De Eugenio D, Dimino TA, Freeny IC, Rovnack MB, Gromelski JS. Medications and Breast-Feeding: A Guide for Pharmacists, Pharmacy Technicians, and Other Healthcare Professionals. Part I. J Pharm Technol 2004;20:17-27. doi: 10.1177/875512250402000106.
  22. Hale T, Kristensen J, Hackett L, Kohan R, Ilett K. Transfer of metformin into human milk. Adv Exp Med Biol. 2004 Abstract
  23. Gardiner SJ, Kirkpatrick CM, Begg EJ, Zhang M, Moore MP, Saville DJ. Transfer of metformin into human milk. Clin Pharmacol Ther. 2003 Abstract Full text (link to original source) Full text (in our servers)
  24. Hale TW, Kristensen JH, Hackett LP, Kohan R, Ilett KF. Transfer of metformin into human milk. Diabetologia. 2002 Abstract Full text (link to original source) Full text (in our servers)

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