Lab Test

Iodine, Urine

Urine Iodine

Test Codes



  • Please refer to the Specimen Collection Manual for instructions on 24 Hour Urine Collection:
  • If this test is used in conjunction with the 131I uptake test, then specimen collection should begin immediately after the dose of 131I is given (i.e., the patient should void and discard urine just prior to the 131I, and all subsequent urine should be collected for the next 24 hours). The last void should be included in the collection.

Specimen Collection Criteria

Collect: 24 hour urine sample with no preservative.

  • Keep 24 hour urine specimen iced or refrigerated during collection.
  • Include start and end dates and times for the collection period on the specimen container.
Urine Preservative Options
No Preservative
6N Hydrochloric Acid
Boric Acid (10g)
Sodium Carbonate
50% Acetic Acid

Physician Office/Draw Specimen Preparation

Maintain specimens refrigerated (2-8°C or 36-46°F) prior to transport.

Preparation for Courier Transport

Transport: Entire 24 hour urine collection, refrigerated (2-8°C or 36-46°F).

Rejection Criteria

Random urine specimens.

Specimens not collected and processed as indicated.

In-Lab Processing

Measure total volume of 24 hour urine specimen. Record total volume and collection start and end dates and times in the LIS system. Aliquot 10.0 mL from the well-mixed 24 hour urine collection. (Minimum: 0.3 mL)


Specimen Stability for Testing:

Room Temperature (20-26°C or 68-78.8°F): 146 days
Refrigerated (2-8°C or 36-46°F): 146  days
Frozen (-20°C/-4°F or below): 146 days

Specimen Storage in Department Prior to Disposal:

Specimen retention time is determined by the policy of the reference laboratory. Contact the Send Outs Laboratory with any questions.


Sent to Mayo Medical Laboratories, Rochester, MN.


Monday – Friday.
Results available in 2-5 days.

Reference Range

By report.

Test Methodology

Inductively Coupled Plasma/Mass Spectrometry (ICP/MS).


Iodine is an essential element that is required for thyroid hormone production.

The measurement of urinary iodine serves as an index of adequate dietary iodine intake.

Daily urinary output of less than 90 mcg/24 hours suggests dietary deficiency.

Values greater than 1000 mcg/specimen may indicate dietary excess, but more frequently suggest recent drug or contrast media exposure.

Administration of iodine-based contrast media and drugs containing iodine, such as amiodarone, will yield elevated results.

Clinical Utility

This assay is used to monitor iodine excretion rate as an index of daily iodine replacement therapy and for correlating total body iodine load with 131I uptake studies in assessing thyroid function.

CPT Codes



Last Updated


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This directory currently reflects information only for specimens collected and/or processed at the
Farmington Hills, Grosse Pointe, Royal Oak, and Troy campuses.