If you are on thyroid medication and taking
your prenatal vitamin (PregVit)

If you have been prescribed levothyroxine (Synthroid, Eltroxin and others) to take first thing in the morning on an empty stomach, then PregVit pink tablet containing iron should be taken 4 hours later. Take your PregVit blue tablet containing calcium as usual in the evening within an hour of your meal. Make sure to have your healthcare professional monitor your thyroid condition during pregnancy.

Iron supplementation, whether alone or as part of a multivitamin supplement, can decrease the absorption of thyroid hormone medication. Therefore, iron supplements taken at the same time as levothyroxine (Synthroid, Eltroxin and others) may interfere with absorption.

Calcium can also interfere with the absorption of thyroid drugs. Simultaneous ingestion of calcium supplement with levothyroxine has been reported to reduce the effectiveness of levothyroxine.

A recent study found that doses of levothyroxine do not need to be modified if prenatal vitamins containing iron and/or calcium are taken 4 hours following the intake of levothyroxine. Continuous medical monitoring of the thyroid status is essential for the well being of both the pregnant woman and the fetus.