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Test ID: UIOD Iodine, 24 Hour, Urine

Reporting Name

Iodine, 24 Hr, U

Useful For

Assessment of iodine toxicity or recent exposure in a 24-hour urine collection


Monitoring iodine excretion rate as index of replacement therapy

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.


Measurement of urinary iodine excretion provides the best index of dietary iodine intake and deficiency is generally indicated when the concentrations are below 100 mcg/L.

Report Available

1 to 3 days

Day(s) Performed

Monday, Wednesday, Friday

Clinical Reference

1. Nader R, Horwath AR, Wittwer CT: Tietz Textbook of Clinical Chemistry and Molecular Diagnostics. Sixth edition. St. Louis. Elsevier 2017

2. 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

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

4. Pfeiffer CM, Sternberg MR, Schleicher RL, et al: CDC’s Second National Report on Biochemical Indicators of Diet and Nutrition in the US Population is a valuable tool for researchers and policy makers. J Nutr 2013;143(6):938S-947S

Method Name

Inductively Coupled Plasma-Mass Spectrometry (ICP-MS)

Specimen Type


Necessary Information

24-Hour volume is required

Specimen Required

Patient Preparation:

1. High concentrations of gadolinium and iodine are known to interfere with most metals tests. If gadolinium- or iodine-containing contrast media has been administered, a specimen should not be collected for 96 hours.

2. 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 dose, and all subsequent urine should be collected for the next 24 hours). The last void should be included in the collection.

Supplies: Urine Tubes, 10 mL (T068)

Container/Tube: Plastic, 10-mL urine tube 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: See Urine Preservatives-Collection and Transportation for 24-Hour Urine Specimens in Special Instructions for multiple collections.

Specimen Minimum Volume

0.3 mL

Specimen Stability Information

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

Reference Values

0-17 years: not established

≥18 years: 75-851 mcg/24 hour

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 US 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

Urine Preservative Collection Options

Note: The addition of preservative or application of temperature controls must occur within 4 hours of completion of the collection.







50% Acetic Acid


Boric Acid


Diazolidinyl Urea


6M Hydrochloric Acid


6M Nitric Acid


Sodium Carbonate






Mayo Clinic Laboratories | Endocrinology Catalog Additional Information: