Is Levothyroxine safe during pregnancy?
What the FDA-approved label for Levothyroxine actually states in its Pregnancy Risk Summary — not a secondhand verdict. The decision is one to make with your prescriber.
What the label’s pregnancy summary says
The label's §8.1 risk summary reports that clinical experience, including postmarketing data, in pregnant women treated with oral levothyroxine to maintain a euthyroid state has not shown increased rates of major birth defects, miscarriage, or other adverse maternal/fetal outcomes. It stresses the opposite concern: untreated hypothyroidism in pregnancy carries real risks (spontaneous abortion, gestational hypertension, pre-eclampsia, stillbirth, premature delivery, and possible adverse effects on fetal neurocognitive development). The label states levothyroxine should not be discontinued during pregnancy and that hypothyroidism diagnosed in pregnancy should be promptly treated. Because thyroid hormone requirements often rise in pregnancy, it advises monitoring TSH and adjusting the dose during pregnancy under a prescriber's care, returning to the pre-pregnancy dose after delivery. Talk to your prescriber; do not stop or change this medicine on your own.
Frequently asked questions
Is Levothyroxine safe to take during pregnancy?
The label's §8.1 does not report a clear risk for Levothyroxine (summary above), which is reassuring but is not the same as a guarantee of safety — no drug is studied in pregnancy the way it is in other adults. Use it in pregnancy only after discussing it with your prescriber. The one universal rule: do not start or stop a medication in pregnancy without medical advice — an untreated condition can carry its own risk to a pregnancy.
What does the FDA label say about Levothyroxine in pregnancy?
The summary above is transcribed from the label's Pregnancy Risk Summary (§8.1). Since 2015 FDA labels replaced the old A/B/C/D/X letter categories with a narrative that describes what human and animal data actually show, which is what you are reading here — not a single letter grade.
Is Levothyroxine safe while breastfeeding?
That is a separate question the label answers in a different section (§8.2, Lactation), and it does not always match the pregnancy verdict. This page covers pregnancy only. For breastfeeding, ask your prescriber or pharmacist, or check the NIH LactMed database, which summarizes the drug-in-breast-milk evidence.
More guides for Levothyroxine
Source
Levothyroxine Sodium — DailyMed FDA label (§8.1 Pregnancy; Boxed Warning; Adverse Reactions) ↗
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The pregnancy information is transcribed from the drug’s FDA-approved label (§8.1) and mirrors what the label states — “insufficient data” is never rounded up to “safe.” This is general reference information, not medical advice. Whether to take any medication in pregnancy is a decision for you and your prescriber; do not start or stop a drug on your own, because an untreated condition can also carry risk.