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.
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 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.
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.