Are You Getting Too Much (Or Too Little) Iodine?


When I talk to my patients about iodine, I’m often met with confused looks and skepticism. And I have to admit, at first glance, iodine does sound like something you would want to avoid rather than get more of. Many people mistake iodine for a heavy metal or toxin when the reality is that iodine is an essential nutrient that many of us could benefit from.

As a functional medicine practitioner, my job is to make you aware of just how much specific nutrients can affect your health — and iodine is the perfect example of this. Keep reading to have all your iodine questions, answered.


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What is iodine?

As I mentioned before, iodine is labeled an “essential nutrient” because the body doesn’t produce it on its own, which means that we have to get it through food, drink, or supplementation. Iodine is a trace mineral that’s found naturally on earth and in certain foods but the tough thing about iodine is that it’s not found in all that many common foods; for example, iodine is found mostly in sea vegetables like seaweed, dulse, and kelp. But how often do you eat kelp? Probably not often — and maybe not ever!

Some other good sources of iodine include:

  • Cod (3 ounces ) - 158 mcg
  • Oysters (3 ounces) - 93 mcg
  • Egg (1 cooked) - 26 mcg
  • Iodized salt (1 gram) - 45mcg

As you can probably guess, iodine deficiencies are common, especially if you’re a vegan. Unless you’re eating kelp, cod, oysters, and multiple eggs almost every day, you may not be getting enough iodine. This can have many consequences in your body but the main one has to do with the thyroid.

How does iodine benefit the thyroid?

Iodine isn’t just important to the thyroid — it’s a part of thyroid hormones themselves. You may have heard of “T3” and “T4” thyroid hormones; well, “3” and “4” stand for the number of iodine atoms it takes to produce each of these hormones. When you don’t get enough iodine, it can influence your thyroid hormone synthesis, which is a problem because the thyroid is largely in control of your metabolic activity. Iodine deficiencies can lead to a condition known as “goiter,” which is characterized by a greatly enlarged thyroid gland that is visible to the naked eye and is accompanied by symptoms like coughing, fast heart rate, inability to tolerate heat, shortness of breath, throat tightness, and weight gain. Iodine deficiency is often an underlying cause of thyroid issues and is something I always look at in my patients with existing or suspected thyroid problems.

That said, unlike vitamin D or C, it’s not as simple as just “getting more iodine.” Why? Because too much iodine (1) can actually increase thyroid antibodies and perpetuate thyroid symptoms. It can even contribute to Hashimoto’s disease, which is an autoimmune thyroid condition that can cause symptoms like skin dryness, hair loss or dryness, constipation, depression, fatigue, joint stiffness, muscle weakness, puffy eyes, sensitivity to cold, swelling in extremities, and weight gain.

Before you substitute with iodine it’s important to get your thyroid tested by a professional who can guide you towards thyroid balance. If you get a thyroid test, make sure your doctor tests you for:

  • Free T4: This will tell you the levels of free or active form of T4. This will be low in cases of hypothyroidism but can be normal in subclinical, early stages of thyroid dysfunction. Lab range: 0.8-1.8 ng/DL Optimal range: 1.0-1.5 ng/DL
  • Total T3: This lab shows us the total amount of the metabolically active thyroid hormone. It allows a doctor to check your body’s ability to convert T4 to T3 and to rule out an overactive thyroid. Lab range: 80-200 ng/DL Optimal range: 100-180 ng/DL
  • Thyroid Antibodies: High levels of thyroid antibodies show an autoimmune attack against the thyroid. The overwhelming majority of low thyroid cases are on the autoimmune spectrum, the most common being Hashimoto’s disease. Thyroid Peroxidase (TPO) Ab optimal range: 0-15 IU/mL Thyroglobulin Ab optimal range: 0-0.9 IU/m

As a general rule, always test your thyroid before you supplement with iodine!

How do you make sure you’re getting the right amount of iodine?

Correcting an iodine deficiency isn’t as easy as many other nutrients. For example, correcting a magnesium deficiency can involve eating more nuts and seeds, leafy greens, or yogurt; correcting a vitamin D deficiency can be as simple as getting direct sunlight for 20 minutes a day. Iodine isn’t quite so simple. For one, it’s not found in a ton of different foods that we want to incorporate into our lives daily, and second, some people are already getting too much iodine. Yes, you heard that correctly! Iodine excess is also a real problem many people face. That’s just another reason why it’s important to get your thyroid tested first and only supplement with iodine if it’s really necessary. 

Once you get your test done, you’ll either need to cut back on iodine or increase it. Here’s what I recommend for both:

1. Too much iodine: Be mindful of salt

If you get tested and find that you’re actually getting too much iodine, salt might be the culprit. Studies are looking into the rise of iodized salt and its connection to iodine-excess thyroid issues. By fortifying table salt with iodine we could be unknowingly contributing to the rise in thyroid problems through too much iodine intake. Switching to sea salt is one way to ensure you aren’t overdoing it on iodine. While sea salt does contain a small amount of naturally-occurring iodine, it’s not enough to make a significant difference in your overall iodine levels therefore this shouldn’t be something to rely on if you are looking to incorporate more iodine into your diet.

2. Too little iodine: Take an iodine supplement

The recommended intake of iodine varies for each individual but in general, adult men and women should be getting 150 mcg of iodine per day and pregnant women 220 mcg per day. If you and your doctor determine that supplementation is necessary, I recommend letting them instruct you on the appropriate dosage and retest your thyroid regularly to make sure you’re never overdoing it.

Iodine is one of those often forgotten nutrients, but it’s extremely important to have balanced iodine levels if you want to have a healthy thyroid and a healthy metabolism. At your next check-in with your doctor, have them check your thyroid and make sure iodine is part of the conversation. Your thyroid will thank you!

As one of the first functional medicine telehealth clinics in the world, we provide webcam health consultations for people around the globe. 


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  1. Leung AM, Braverman LE. Consequences of excess iodine. Nat Rev Endocrinol. 2014;10(3):136-142. doi:10.1038/nrendo.2013.251

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Dr. Will Cole, DNM, IFMCP, DC is a leading functional medicine expert who consults people around the globe, starting one of the first functional medicine telehealth centers in the world. Named one of the top 50 functional and integrative doctors in the nation, Dr. Will Cole provides a functional medicine approach for thyroid issues, autoimmune conditions, hormonal imbalances, digestive disorders, and brain problems. He is the host of the popular The Art Of Being Well podcast and the New York Times bestselling author of Intuitive Fasting, Ketotarian, The Inflammation Spectrum, and Gut Feelings: Healing the Shame-Fueled Relationship Between What You Eat and How You Feel.

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