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Iodine Excretion Urine Test

Last updated June 2, 2019

Approved by: Krish Tangella MD, MBA, FCAP

The Iodine Excretion Urine Test measures the amount of iodine that is excreted through urine to determine iodine levels in the body.

What are other Names for this Test? (Equivalent Terms)

  • Iodine Excretion 24-Hour Urine Test

What is Iodine Excretion Urine Test? (Background Information)

  • Iodine is an essential element for the formation of T3 (triiodothyronine) and T4 (thyroxine), two hormones made by the thyroid gland. The thyroid hormones T3 and T4 stimulate the metabolism, increasing growth and development
  • Iodine is obtained mainly from the diet. Without iodine, the production of T3 and T4 by the thyroid gland stalls. This can lead to the formation of a goiter in the neck as levels of fluid and hormone precursors accumulate
  • Excessive iodine levels may also cause thyroid gland malfunction. However, iodine deficiency and the hypothyroidism that results are the most common disorders associated with iodine
  • The Iodine Excretion Urine Test measures the amount of iodine that is excreted through urine to determine iodine levels in the body. Individuals experiencing an iodine deficiency excrete very low amounts of iodine in their urine

What are the Clinical Indications for performing the Iodine Excretion Urine Test?

Following are the clinical indicators for performing the Iodine Excretion Urine Test:

  • Following up to thyroid-stimulating hormone (TSH) and free T3 tests
  • Early or late onset of puberty
  • Distinguishing between primary and secondary hypogonadism
  • Masculinization in females, such as excessive hair growth
  • Infertility
  • Decreased sex drive
  • Erectile dysfunction
  • Diminished menstrual cycle
  • Abnormal uterine bleeding

How is the Specimen Collected for Iodine Excretion Urine Test?

Following is the specimen collection process for Iodine Excretion Urine Test:

Sample required: Urine

Process of obtaining a sample in adults: Urination into a sterile container over a 24-hour period.

Preparation required: It is recommended to drink 6 to 8 glasses of water or other fluids prior to the test.

What is the Significance of the Iodine Excretion Urine Test Result?

The interpretation for the values of the Iodine Excretion Urine Test is as follows:

  • Severe deficiency: 0-0.19 µmol/L
  • Moderate deficiency: 0.20-0.38 µmol/L
  • Mild deficiency: 0.39-0.78 µmol/L
  • Normal: 0.79-1.56 µmol/L
  • Slight excess: 1.57-2.36 µmol/L
  • Severe excess: Over 2.37 µmol/L

The significance of the Iodine Excretion Urine Test result is explained.

  • A high value for the test may point to a diagnosis of:
    • Excessive intake through the diet
    • Recent drug or contrast media exposure
  • A low value for the test may point to a diagnosis of dietary deficiency.

The laboratory test results are NOT to be interpreted as results of a "stand-alone" test. The test results have to be interpreted after correlating with suitable clinical findings and additional supplemental tests/information. Your healthcare providers will explain the meaning of your tests results, based on the overall clinical scenario.

Additional and Relevant Useful Information:

  • Certain factors interfere with the results of the Iodine Excretion Urine Test. These include altitude, pregnancy, age, strenuous exercise, and nutrition status
  • Iodine is often added to salt in the United States to decrease the incidence of iodine deficiency in the population

Certain medications that you may be currently taking may influence the outcome of the test. Hence, it is important to inform your healthcare provider, the complete list of medications (including any herbal supplements) you are currently taking. This will help the healthcare provider interpret your test results more accurately and avoid unnecessary chances of a misdiagnosis.

The following DoveMed website links are useful resources for additional information:




Please visit our Laboratory Procedures Center for more physician-approved health information:


References and Information Sources used for the Article:

Helpful Peer-Reviewed Medical Articles:

Reviewed and Approved by a member of the DoveMed Editorial Board
First uploaded: June 3, 2016
Last updated: June 2, 2019