Although Synthroid does pass through breast milk, it does not appear to cause any problems for the nursing infant. In fact, women who have an underactive thyroid may not be capable of lactating properly without treatments such as Synthroid. If you are thinking about taking Synthroid and breastfeeding at the same time, talk to your healthcare provider about the best treatment options for your situation.
Synthroid and Breastfeeding: An Overview
Synthroid® (levothyroxine sodium) passes through breast milk in humans, although it does not seem likely to cause any problems. If you are breastfeeding a child, you should talk with your healthcare provider about taking Synthroid.
Synthroid and Breastfeeding: What Does the Research Say?
Studies have shown that Synthroid passes through breast milk, just like natural thyroid hormones. If your thyroid hormone levels are kept at normal levels, there is no reason to expect that Synthroid would cause any problems during breastfeeding. In fact, women with an underactive thyroid (hypothyroidism) may not be capable of lactating properly unless they are treated, whether with Synthroid or other forms of thyroid replacement.
Only small amounts of Synthroid pass through breast milk. This is not enough to treat an underactive thyroid in an infant. Instead, the infant must be treated directly.
Talking With Your Healthcare Provider About Synthroid and Breastfeeding
You should talk with your healthcare provider about Synthroid and breastfeeding. Each woman's situation is different, and you and your healthcare provider understand your situation best. After considering what you want and expect, as well as your current health situation, the two of you can make a shared decision about Synthroid and breastfeeding that is right for you. In general, Synthroid is considered safe for women who are breastfeeding and for their infants.
Written by/reviewed by: Kristi Monson, PharmD;Arthur Schoenstadt, MD
Last reviewed by: KristiMonson, PharmD;
List of references (click here):
Synthroid [package insert]. North Chicago, IL: Abbott Laboratories;2002 July.
Briggs GG, Freeman RK, Yaffe SJ. Drugs in Pregnancy and Lactation. 7th ed. Philadelphia (PA): Lippincott Williams & Wilkins;2005.
National Library of Medicine (US). Drugs and Lactation Database (LactMED). NLM Web site. Available at: http://toxnet.nlm.nih.gov/cgi-bin/sis/htmlgen?LACT. Accessed November 6, 2007.
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