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Test ID: ICRU Iodine/Creatinine Ratio, Random, Urine

Reporting Name

Iodine/Creat Ratio, Random, U

Useful For

Assessment of iodine toxicity or recent exposure when a 24-hour urine cannot be collected


Monitoring iodine excretion rate as index of replacement therapy when a 24-hour urine cannot be collected

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. For deficiency, 10 repeat random urines are recommended.

Profile Information

Test ID Reporting Name Available Separately Always Performed
ICR Iodine/Creat Ratio, U No Yes
CDCR Creatinine Concentration No Yes

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

ICR: Inductively Coupled Plasma-Mass Spectrometry (ICP-MS)

CDCR: Enzymatic Colorimetric Assay

Specimen Type


Ordering Guidance

Due to the significant variation in the rate of secretion over the course of a day, a 24-hour collection is preferred. For more information see UIOD / Iodine, 24 Hour, Urine.

Specimen Required

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

Supplies: Urine Tubes, 10 mL (T068)

Collection Container/Tube: Clean, plastic urine collection container

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

Specimen Volume: 3 mL

Collection Instructions:

1. Collect a random urine specimen.

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

Specimen Minimum Volume

1 mL

Specimen Stability Information

Specimen Type Temperature Time Special Container
Urine Refrigerated (preferred) 30 days
  Ambient  30 days
  Frozen  30 days

Reference Values

0-17 years: not established

≥ 18 years: <584 mcg/g creatinine

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
ICRU Iodine/Creat Ratio, Random, U 55928-6


Result ID Test Result Name Result LOINC Value
CDCR Creatinine Concentration 2161-8
32874 Iodine/Creat Ratio, U 55928-6
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