If too much iodine can cause thyroid disease, how do you know if you are getting too much?

It is a logical question, and thankfully there are ways to test. However, most tests are not accurate, and in many cases, testing is not helpful. This article will help you decide if you need to test your iodine and how to do so accurately.

When Should You Test Iodine?

In medicine, tests are only helpful if their answers would change something. If a person broke their leg and needed surgery, it could be possible that osteoporosis contributed to the break. However, there would be no reason to delay an urgent surgery for a bone density test unless it would change how the surgery would be performed.

Before the diet – No

It is not helpful to test iodine before starting The Thyroid Reset Diet because the studies show that iodine tests do not predict how people will respond. One might assume that those with high iodine tests could find the Thyroid Reset Diet helpful, while those with low iodine tests would not.

It turns out that the amount of iodine stored in the thyroid before starting the diet is not always reflected by the amount of iodine on an iodine test.

If the diet does not help – Yes

Let’s say that you cut out iodine from personal care products, supplements, and medications – and you have carefully followed the Thyroid Reset Diet for at least one month, yet nothing got better. You saw no changes in symptoms, and your thyroid levels did not change.

In this case, you would want to test your iodine.

How To Test Iodine

The most useful test for our purposes is the urinary iodine to creatinine ratio. Please note that this is NOT the same as urinary iodine or 24-hour urinary iodine.
The amount of iodine in our urine varies greatly. The readings are more helpful when we compare them against a kidney protein called creatinine.

This test is called the urinary iodine to creatinine ratio.

At the time of this writing, there are two labs I know of that offer this option.


LabCorp is a national referencing lab that can report the UIC ratio. You will need a doctor’s order for tests through LabCorp.

Once you have an order, make an appointment at a draw station to leave a urine sample. Only a single sample is needed, and you do not need to do a 24-hour urine collection. In the LabCorp system, the test number for the urinary to creatinine ratio is 070172.

ZRT Labs

The other option is ZRT Labs. You can purchase a test kit from them, and they can ship it to your home. From there, you can collect a urine sample and mail it back to them.

There are some states in which they do not ship test kits. In their system, the test is called ‘Iodine,’ and it is one of their Toxic and Essential Elements tests.

Once you receive your collection kit, follow the directions and send in your sample. They will provide your results via email when completed.

What do your results mean?

Iodine tests cannot tell you how much iodine you care consuming on a given day. If you have been on a low-iodine diet for at least one month, they can tell you if the amount of iodine in your thyroid is in one of three ranges.

The urinary iodine to creatinine (UIC) ratio measures the micrograms (mcg) of iodine in urine and compares it against the grams (G) of creatine. Because of this analysis, the reports are listed in mcg/G UIC.

The following guidelines do not apply to children, pregnant or nursing mothers. As always, speak to your doctor to find the best levels for you.

  • Excess – over 200 mcg/G UIC
  • Maintenance – 50 – 200 mcg/G UIC
  • Detox under 50 mcg/G UIC


If your levels are over 200 mcg/G UIC, you consume more iodine than your thyroid can eliminate. The amounts of iodine in your thyroid are increasing and may be harmful.


If you are between 50 and 200 mcg/G UIC, you are holding steady. If your thyroid function has not improved, you are still getting too much iodine.

If your thyroid function has improved, it can likely stay there in this range. The Thyroid Reset Diet recommends you still freely consume Green Light foods and add up to 2 servings of Yellow Light food per day.


If your levels are under 50 mcg/G IUC, you are successfully following the Reset Guidelines of the Thyroid Reset Diet. Those seeking to improve their thyroid function often stay in this range for 1-9 months.

Iodine is low enough

Let’s say that your iodine comes back in the targeted range. If your symptoms have improved, but your blood levels have not, wait three months and retest your thyroid. If iodine is in the range and neither symptoms nor blood levels have improved, the diet may not work for you yet.

The two top things that could be holding you back include the wrong thyroid medication and hidden causes of thyroid symptoms. You can read more about thyroid medications here and uncovering invisible symptoms here.

Iodine not low enough

If your test shows that your iodine levels are above target, there are two possible issues.

The first is that there are some hidden sources of iodine. Double-check all personal care products, supplements, and foods. Look in the book for some of the lists of hidden sources of iodine, and make sure you’re not getting any.

The second possibility is that you are still detoxing from iodine. If you ingested toxic amounts of iodine, it might take several months for it to get out of your system. In some rare cases, it can even take over six months.

You can suspect this applies to you if you know you had high dose iodine supplements, lots of seaweed in your diet, or if you had iodine as a contrast agent.

If this is the case, it is still worth double-checking to ensure you found all the hidden sources of iodine. Keep being careful and recheck your thyroid and your iodine levels in 3 months.

Non-Recommended Tests

There are many other ways to test for iodine. Many of these are more commonly available. Some of them are good for other uses, several of them have no legitimate usage. I’ll mention each briefly.

Please know that if you have results from any of these tests, they are not meaningful. Consider whether or not you even need to test. If you do, please do so in a way that will be accurate. Health is too important to leave to chance.
Valid test for other applications

Urinary iodine 24-hour urinary iodine

Since most iodine is eliminated through the kidneys, urine iodine does have a relationship with the body’s iodine status. These tests are not useful because they are only accurate when used at a population level.

These tests are excellent when used for large groups. When more than 500 people have this test done, one can accurately evaluate the whole group’s iodine status, but not any individual within the group.

Studies have shown that if one individual wanted to find their nutritional iodine status, they would have to test their urine well over 400 times to be even within 90% accuracy. This is not practical for anyone! And a single reading can be misleadingly high or low.

It might seem that collecting urine for 24 hours would be more accurate than just collecting the urine at one sample. It is, but not enough to be helpful. Rather than needing 400 random tests, 24-hour tests still require you to do over 300 tests to be accurate.

Could you imagine collecting all of your urine for nearly an entire year? Thankfully there are easier options.

Serum Thyroglobulin

There is a blood test called serum thyroglobulin. This is not the same as anti-thyroglobulin antibodies. It is a measurement of the main protein made by the thyroid. When thyroid cells die, thyroglobulin spills into the bloodstream.

High levels of iodine can make thyroglobulin lower, and low levels of iodine can make thyroglobulin higher. However, if someone has thyroid disease, this relationship is not accurate.

Therefore Serum thyroglobulin is not a helpful test for iodine for anyone who has thyroid disease.

Serum iodine

Serum iodine is the same as iodine in the blood. This is a good test when checking someone who is exposed to enough iodine to hurt their kidneys. The most common way this test is useful is when someone is given a medicine like amiodarone that has an amount of iodine that can stay in the body for 3 to 6 months.

Serum levels only get high when one is exposed to an extremely high amount of iodine. They do fluctuate up and down, but they do not reflect iodine’s nutritional status within or below the normal range.

If your blood level of iodine said you were low, that does not mean you are deficient in iodine. However, if your blood level says you are elevated, you are getting too much. Yet, the amount needed to have iodine elevate in your blood is generally much higher, and people are ever exposed to.

Having normal amounts of iodine in the serum doesn’t mean that you aren’t getting too much for your thyroid.

No Valid Application

There are popular iodine tests that are simply not accurate and have no legitimate role in medicine. Unfortunately, these are often talked about and recommended by various practitioners.

Skin patch test

In the iodine skin test, people apply a colored liquid form of iodine like Betadine to the skin. The rationale is that if your body needs iodine, you will absorb it more quickly. However, this is simply not true.

When you apply iodine to your skin, some become invisible because they oxidize when exposed to the air. Some of it does get absorbed into the bloodstream. However, your body has no way of preferential absorbing it when you need it. Scientists debunked this test as far back as 1932.

Urine challenge test AKA iodine loading test

The iodine challenge test involves taking a dangerously high dose of iodine and collecting urine for the following 24 hours. The rationale is that if your body does not eliminate all of the iodine right away, you must have needed it.
Yet we know that the body can be exposed to waste or toxins that it cannot eliminate immediately. When the iodine intake of a population changes, their urine writing levels do change. However, this change takes three to four months, not 24 hours.

A laboratory did a test recently to check on the accuracy of the urine iodine challenge test. They showed that people did eliminate more iodine after a high iodine dose, but it took them many days to get rid of it. Twenty-four hours were not enough.

This test is not accurate, and the amount of iodine used for it is not safe.

Hair iodine

I mentioned this mostly for completion. Several years ago, it was proposed that iodine in the hair could gauge the nutritional status of iodine. The one published study that made this claim was retracted a few months after publication.

If you have a hair test, please know that iodine levels in your hair, do not reflect your iodine requirements.

In Closing

Iodine testing is an unusual topic because it generates much more interest than it deserves.

Most people have no reason to test their iodine. Anyone with thyroid disease can safely start on the thyroid reset diet and see if they improve.

Thankfully this is one test that most will not need to worry about.

  • General health, pre TRD – no benefit to testing iodine
  • Did not respond – good to test iodine

Appendix – How to calculate from other tests

If you have a urinary iodine test and a urinary creatinine test that were taken at the same time, you can use them to calculate urinary iodine to creatinine ratio. Here is how the math works.

You will need to find your iodine results in mcg/L and your creatinine results in mg/dL. These are the most common units by far. If your results are not in these units, you may not be able to make use of them.

  • Step 1. Make note of your iodine results in micrograms (mcg) per Liter (L). It will look like the report below. The symbol µg is the same as mcg. The sample below, the number you want is 255.8.
  • Step 2. Make note of your urinary creatinine level. It should be in milligrams per deciliter (mg/dL). Please note that serum (blood) creatinine is not the same and will not work. In the sample below, 45.5 is the number you want.
  • Step 3. We need to convert creatinine from mg/dL to G/L. To do that, multiply your creatine results by 0.01. That will give you creatinine in mg/dL. For the sample results, we would multiply 45.5 * 0.01 and get 0.455.
  • Step 4. Divide urinary iodine by G/L of creatinine. For the sample numbers we would enter into the calculator ‘255.8➗0.455’. The result would be 562 UIC.
  • Step 5. See the section above ‘What do your results mean?’ In the sample above, 562 is deep in the range of excess iodine. The creatinine correction more than doubled the uncorrected iodine reading of 255.8.
P.S. Whenever you are ready, here is how I can help you now:

1. Schedule a Thyroid Second Opinion with me, Dr. C, Click Here for Details
2. Download and use my Favorite Recipes Cookbook Here
3. Check out my podcast Medical Myths, Legends, and Fairytales Here

Dr. Alan Glen Christianson (Dr. C) is a Naturopathic Endocrinologist and the author of The NY Times bestselling Adrenal Reset Diet, The Metabolism Reset Diet and The Thyroid Reset Diet.

Dr. C’s gift for figuring out what really works has helped hundreds of thousands of people reverse thyroid disease, lose weight, diabetes, and regain energy. Learn more about the surprising story that started his quest.