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Iodine & Synthroid Interaction

author image Adam Cloe Ph.D./M.D.
Adam Cloe has been published in various scientific journals, including the "Journal of Biochemistry." He is currently a pathology resident at the University of Chicago. Cloe holds a Bachelor of Arts in biochemistry from Boston University, a M.D. from the University of Chicago and a Ph.D. in pathology from the University of Chicago.
Iodine & Synthroid Interaction
A pharmacist is counseling a young woman. Photo Credit: Thinkstock Images/Stockbyte/Getty Images

Hypothyroidism is caused by poor thyroid function and can cause a lack of energy, cold intolerance, constipation and other problems. Both iodine supplements and Synthroid can be taken to treat hypothyroidism. There is no interaction between iodine and Synthroid, unless you have an iodine deficiency. Talk to your doctor before consuming iodine supplements, as this mineral may interact with other drugs.

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Iodine and Thyroid

The thyroid gland produces hormones that regulate the metabolism of your cells. A lack of thyroid hormone causes your metabolism to be abnormally low. Iodine is a mineral that can be found in seafood, some plants and is also added to many commercially available kinds of salt. Iodine is needed to make thyroid hormone, so an iodine deficiency can cause hypothyroidism. Iodine-deficiency hypothyroidism can be treated with iodine supplements.


Synthroid is a brand name for the medication levothyroxine. This drug is a synthetic form of thyroid hormone, and you may take it to treat any disorder that causes your thyroid gland to not make enough hormones. Levothyroxine doses vary depending on the extent of your hypothyroidism. This medication is best absorbed when taken on an empty stomach, and overdose of this medication can cause hyperthyroidism.

Iodine and Thyroid Interaction

In the case of an iodine deficiency, taking iodine along with levothyroxine can cause hyperthyroidism, because the iodine will restore normal thyroid function, causing the Synthroid to be unnecessary. However, this interaction only occurs if hypothyroidism is due to an iodine deficiency. Otherwise, has no listed interaction between Synthroid and iodine. However, you should avoid taking Synthroid with iodine-containing foods, such as seafood, as the food will decrease the absorption of thyroid hormone.


Iodine deficiencies are rare in developed countries due to supplementation of salt with iodine. Thus, taking iodine supplements is unlikely to help hypothyroidism symptoms unless you have been definitively diagnosed with a deficiency. Talk to your doctor before taking iodine, as iodine can interact with other medications, such as lithium, a commonly used mood stabilizer. You should also tell your doctor about all medications and supplements that you take if he prescribes Synthroid.

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