Synthroid and Breastfeeding
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 OverviewSynthroid® (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.