Is Levothyroxine Safe in Pregnancy

Status

caution Last reviewed: 2026-05-16 · Confidence: high

Reason

Used in pregnancy when needed. Untreated hypothyroidism is risky. Dose often needs adjustment and monitoring.

Drug Information

Brand Name
Synthroid, Levoxyl, Unithroid, Tirosint, Levo-T
Generic Name
levothyroxine
Drug Class
Thyroid hormone replacement
FDA Category
N/A (PLLR narrative label)
Rx Status
prescription

Safe Amount

Dosage must be determined by your provider based on individual risk/benefit.

Effects

Pregnancy
Do not stop on your own. TSH should be checked and dose adjusted during pregnancy and after delivery.
Mother
Pregnancy can increase levothyroxine needs. Poorly treated hypothyroidism raises risk of pregnancy complications.
Baby
Not linked to higher birth defect or miscarriage rates in official labeling. Untreated maternal hypothyroidism can harm fetal growth and development.

Trimester Notes

1st Trimester
Usually continued if you already take it. Untreated hypothyroidism early in pregnancy can be harmful.
2nd Trimester
Dose needs may rise as pregnancy continues. TSH monitoring is important.
3rd Trimester
Continue monitoring. Dose may need adjustment. Return to pre-pregnancy dose after delivery unless your prescriber says otherwise.

Risk-Benefit Note

Maintaining normal thyroid levels in pregnancy is important. Official labeling says levothyroxine should not be discontinued during pregnancy.

Conditions & Warnings

  • Consult OB/GYN or prescriber
  • Hypothyroidism
  • Dose monitoring needed in pregnancy
  • Postpartum dose review needed

Alternatives

  • No direct over-the-counter substitute
  • If thyroid treatment is needed, your prescriber may adjust levothyroxine dose
  • Ask your prescriber before changing thyroid medicines

References

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