Iodine and Warfarin

Iodine is an essential nutrient found naturally in the body, needed for the normal metabolism of cells. Humans need iodine for normal thyroid function including the production of hormones. Since the body cannot make iodine, it must come from the diet.

Where is Iodine found?

According to the National Institutes of Health, Iodized salt -- table salt with iodine added -- is the main food source of iodine. Seafood is naturally rich in iodine including cod, sea bass, haddock, perch, and shellfish. Kelp is the most common vegetable seafood that is a rich source of iodine. Dairy products from cattle fed grain grown in iodine-rich soil can be high in iodine.

Many vitamins and vitamin supplements (including liquid forms) may also contain iodine, so read all labels carefully.

Iodine is also used to for radiation emergencies; it works to protect the thyroid gland against radioactive iodides. Potassium iodide should only be used in a radiation emergency, not in advance of an emergency to prevent sickness.1

Interactions with Warfarin?

Iodine and warfarin represents a drug interaction with warfarin that will likely affect INR over time. Patients consuming higher than normal quantities of foods high in iodine over a period of time can expect to see in increase in INR test results.2

Patients looking to boost their Omega-3 Fatty Acid consumption may be increasing their iodine intake without knowing it. The increase of foods from the sea may also impact INR. As always, discuss your diet and medications with your doctor.

  1. U.S. Food and Drug Administration. Frequently Asked Questions on Potassium Iodide (KI). 2011.
  2. Jellin, F. (2005). Natural Medicines Comprehensive Database, p.1268.