Last update Dec. 8, 2017



Safe substance and/or breastfeeding is the best option.

Synthetic preparation of human thyroid hormone T3 used in the treatment of hypothyroidism.

Since the last update, we have not found published data on its excretion in breast milk.

T3 is a natural component of breast milk, found in small concentrations that may or may not depend on plasma levels (Zhang 2013, Oberkotter 1989, Jansson 1983, Mizuta 1983, Sato 1979). Its concentration in breast milk is much higher than that of levothyroxine (T4), which is usually undetectable (Jansson 1983, Sato 1979).

Until there is more published data on this drug in relation to breastfeeding, safer known alternatives (levothyroxine) may be preferable, especially during the neonatal period and in case of prematurity.

Associations which are experts in thyroid diseases recommend treatment with levothyroxine in breastfeeding mothers affected by hypothyroidism (Alexander 2017).

See below the information of this related product:


  • Levothyroxine (Safe substance and/or breastfeeding is the best option.)

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

T3 is Liothyronine Sodium in Abbreviation.

Is written in other languages:

T3 is also known as


T3 belongs to this group or family:


Main tradenames from several countries containing T3 in its composition:


Variable Value Unit
Oral Bioavail. 95 %
Molecular weight 651 daltons
pKa 8.5 -
Tmax 1 - 4 hours
48 - 60 hours


  1. Alexander EK, Pearce EN, Brent GA, Brown RS, Chen H, Dosiou C, Grobman WA, Laurberg P, Lazarus JH, Mandel SJ, Peeters RP, Sullivan S. 2017 Guidelines of the American Thyroid Association for the Diagnosis and Management of Thyroid Disease During Pregnancy and the Postpartum. Thyroid. 2017 Abstract Full text (link to original source) Full text (in our servers)
  2. Zhang Q, Lian XL, Chai XF, Bai Y, Dai WX. [Relationship between maternal milk and serum thyroid hormones in patients with thyroid related diseases]. Zhongguo Yi Xue Ke Xue Yuan Xue Bao. 2013 Abstract
  3. 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.
  4. Oberkotter LV. Analysis of term human milk concentrations of 3,5,3'-triiodo-L-thyronine by high-performance liquid chromatography and radioimmunoassay: correlation with circulating serum levels in lactating women. J Chromatogr. 1989 Abstract
  5. Jansson L, Ivarsson S, Larsson I, Ekman R. Tri-iodothyronine and thyroxine in human milk. Acta Paediatr Scand. 1983 Abstract
  6. Mizuta H, Amino N, Ichihara K, Harada T, Nose O, Tanizawa O, Miyai K. Thyroid hormones in human milk and their influence on thyroid function of breast-fed babies. Pediatr Res. 1983 Abstract
  7. Sato T, Suzuki Y. Presence of triiodothyronine, no detectable thyroxine and reverse triiodothyronine in human milk. Endocrinol Jpn. 1979 Abstract

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