When you’re pregnant and taking Synthroid, a brand name for levothyroxine, a synthetic form of the thyroid hormone T4 used to treat hypothyroidism. Also known as levothyroxine, it’s one of the most commonly prescribed medications for thyroid disorders—and it’s not just safe during pregnancy, it’s often essential. Your thyroid works harder when you’re expecting, and if your body can’t make enough hormone on its own, skipping Synthroid can put both you and your baby at risk.
Many women find their Synthroid dose needs to go up during pregnancy—sometimes by 30% or more—especially in the first trimester. That’s because pregnancy increases thyroid-binding proteins, which makes more hormone bound and less available. Your doctor will likely check your TSH levels every 4 to 6 weeks early on, then adjust your dose as needed. Left untreated, low thyroid levels can lead to miscarriage, preterm birth, or even lower IQ in the child. But with proper monitoring, women on Synthroid have just as healthy pregnancies as those without thyroid issues.
It’s not just about the dose. You also need to know how to take it right. Synthroid should be taken on an empty stomach, at least 30 to 60 minutes before breakfast, and at least 4 hours apart from prenatal vitamins or calcium supplements. Iron, antacids, and even soy milk can interfere with absorption. If you miss a dose, take it as soon as you remember—unless it’s close to your next dose. Don’t double up.
Some women worry about long-term effects, but decades of research show Synthroid doesn’t cross the placenta in harmful amounts. The hormone your baby needs comes from your bloodstream, and your body adjusts to supply it safely. In fact, your baby relies on your thyroid hormone until their own thyroid kicks in around week 12. That’s why stopping or cutting back without medical advice is dangerous.
Postpartum, your dose may drop back down, sometimes to your pre-pregnancy level. But don’t guess—get your TSH checked 6 to 8 weeks after delivery. Hormones shift fast after birth, and your thyroid needs might change again. Breastfeeding? Synthroid is safe. Only tiny amounts pass into milk, and studies show no effect on the baby’s thyroid function.
You’ll find real, practical advice from posts that dig into how thyroid meds work during pregnancy, what lab numbers to track, how to handle side effects, and why some women need more than just Synthroid. There’s no fluff—just clear answers from doctors, pharmacists, and patients who’ve been there. Whether you’re newly pregnant, planning to be, or just confused about your dose, these posts give you the facts you need to stay in control.
Thyroid medication doses must increase by 20-30% during pregnancy to support fetal brain development. TSH should be kept under 2.5 mIU/mL in the first trimester, with testing every 4 weeks. Levothyroxine is safe and essential - delaying adjustments can impact your child's IQ.
