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Test ID UIOD Iodine, 24 Hour, Urine

Reporting Name

Iodine, 24 Hr, U

Useful For

Monitoring iodine excretion rate as an index of daily iodine replacement therapy


Correlating total body iodine load with (131)I-uptake studies in assessing thyroid function

Specimen Type


Specimen Required

Container/Tube: Plastic, 10-mL urine tube (T068) or clean, plastic aliquot container with no metal cap or glued insert

Specimen Volume: 10 mL

Collection Instructions:

1. Collect urine for 24 hours.

2. Refrigerate specimen within 4 hours of completion of 24-hour collection.

3. See Trace Metals Analysis Specimen Collection and Transport in Special Instructions for complete instructions.

Additional Information:

1. 24-Hour volume is required.

2. See Urine Preservatives-Collection and Transportation for 24-Hour Urine Specimens in Special Instructions for multiple collections.

3. If this test is used in conjunction with the (131)I uptake test, then specimen collection should begin immediately after the dose of (131)I is given (ie, the patient should void and discard urine just prior to the (131)I, and all subsequent urine should be collected for the next 24 hours). The last void should be included in the collection.

Specimen Minimum Volume

0.3 mL

Specimen Stability Information

Specimen Type Temperature Time
Urine Refrigerated (preferred) 146 days
  Ambient  146 days
  Frozen  146 days

Reference Values

0-15 years: not established

≥16 years: 93-1,125 mcg/specimen

Day(s) and Time(s) Performed

Monday, Tuesday, Wednesday, Friday; 5 p.m.

Test Classification

This test was developed and its performance characteristics determined by Mayo Clinic in a manner consistent with CLIA requirements. This test has not been cleared or approved by the U.S. Food and Drug Administration.

CPT Code Information


LOINC Code Information

Test ID Test Order Name Order LOINC Value
UIOD Iodine, 24 Hr, U 2492-7


Result ID Test Result Name Result LOINC Value
9549 Iodine, 24 Hr, U 2492-7
TIME5 Collection Duration 13362-9
VL23 Urine Volume 3167-4
3346 Iodine Concentration 26842-5

Clinical Information

Iodine is an essential element for thyroid hormone production. The measurement of urinary iodine serves as an index of adequate dietary iodine intake.


Daily urinary output <90 mcg/specimen suggests dietary deficiency.


Values >1,000 mcg/specimen may indicate dietary excess, but more frequently suggest recent drug or contrast media exposure.

Clinical Reference

1. Knudsen N, Christiansen E, Brandt-Christensen M, et al: Age- and sex-adjusted iodine/creatinine ratio. A new standard in epidemiological surveys? Evaluation of three different estimates of iodine excretion based on casual urine samples and comparison to 24 h values. Eur J Clin Nutr 2000;54:361-363

2. Liberman CS, Pino SC, Fang SL, et al: Circulating iodine concentrations during and after pregnancy. J Clin Endocrinol Metab 1998;83:3545-3549

Analytic Time

1 day

Method Name

Inductively Coupled Plasma-Mass Spectrometry (ICP-MS)

Urine Preservative Collection Options







6N HCl


50% Acetic Acid








Boric Acid