What Does Lugol's Iodine Test for?

Written by cl hendricks
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In 1829, French physician Jean Guillaume Auguste Lugol created a solution of potassium iodide and elemental iodine in distilled water. Called Lugol's iodine, the solution has been used as a disinfectant, antiseptic and to disinfect drinking water during an emergency.

Over time, it has been discovered that Lugol's iodine is useful for testing a number of things. From testing for starch, to testing for vaginal cancer cells, to testing for thyroid function, Lugol's iodine has been both diagnostic and preventive.

Testing for Starch

Fruits, vegetables and other organic compounds that contain starch carbohydrates can be identified with the application of Lugol's iodine. If carbohydrates are present in the compounds, they will turn black or dark blue when Lugol's iodine is applied. Starches most easily identified are plant starches such as amylase and amylopectin, or glycogen contained in animal cells.

Testing for Cancer

When abnormalities in the wall of the cervix or cervical canal are detected during a routine pap smear, a colposcopy, known as a Schiller's test, may be ordered. When this second test is performed, a vinegar-like solution is applied to the cervical canal and cervix, after which Lugol's iodine is applied.

When the iodine solution is applied, healthy tissue will stain brown. Despite the application of the staining Lugol's iodine, abnormal cells will appear white or yellow. If abnormal tissue is confirmed with the Schiller's test, it will then be biopsied and sent to a cytopathologist, a specialist in cellular disease diagnosis, for positive identification.

Iodine and Thyroid Function

Without enough iodine, the thyroid cannot produce enough thyroid hormones for good health. This iodine deficiency is responsible for goitre, which result when an iodine-starved thyroid gland begins to swell as it tries to trap more iodine from the body. A goitre can swell to the point of being the size of a large grapefruit or even larger on the front of the neck, under the chin. This became evident in Michigan in the 1930s, when nearly 40 per cent of the people had a goitre due to the lack of iodine in the soil.

In 1924, iodine was added to table salt and first introduced in Michigan and other Great Lakes and Plains states that were part of the "goitre belt." By1940, iodised salt was in general use; however, even today, iodine deficiency can still be found in certain areas of the world.

Testing for Iodine Absorption

Today, you can easily conduct a simple experiment to see if you body has enough iodine to ensure thyroid hormone production. Even those who have been diagnosed with hypothyroidism and are taking oral supplemental thyroid hormones can test their iodine levels. Insufficient levels of iodine can prevent even the supplemental thyroid hormones from being effective.

You can purchase Lugol's iodine solution at your local pharmacy if you ask for it. You can also purchase it online without a prescription.

The Lugol's iodine thyroid test is an easy, do-it-yourself test that does not require a doctor's blessing or assistance. Use an eyedropper or brush to paint a 3-inch stain on your belly or upper thigh. Check frequently during a 24-hour period. If the stain disappears in less than 24 hours, it means the iodine has been absorbed by a body and thyroid craving iodine. You are iodine deficient.

The same test can be used to correct your body's iodine levels. As insufficient iodine levels cause the iodine stain to be absorbed very rapidly, you can begin to "feed" your body the iodine that it needs. When the stain disappears, reapply the Lugol's iodine again and continue checking to see if the stain has disappeared.

Gradually, as your body absorbs enough iodine, the stain will take longer to disappear. Once the patch is still evident after 24 hours, stop the test. Your body should have enough iodine to aid in proper thyroid hormone production or use of supplemental thyroid hormones.


If you have been diagnosed with hyperthyroidism or an overactive thyroid, DO NOT use Lugol's iodine solution to perform an iodine/thyroid function test. Your body is producing more than enough thyroid hormone already.


The Lugol's iodine thyroid test should be repeated on a monthly basis if you are being treated for hypothyroidism or underactive thyroid.

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