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Test ID ICRU Iodine/Creatinine Ratio, Random, Urine

Reporting Name

Iodine/Creat Ratio, Random, 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

Profile Information

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

Specimen Type


Specimen Required

Collection Container/Tube: Clean, plastic urine collection container

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

Specimen Volume: 2 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

0.5 mL

Specimen Stability Information

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

Reference Values

16-40 years: 70-530 mcg/g Creatinine

41-70 years: 70-860 mcg/g Creatinine

>70 years: 70-1,150 mcg/g Creatinine

Reference values have not been established for patients that are <16 years of age.

Day(s) and Time(s) Performed

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

Test Classification

See Individual Test IDs

CPT Code Information

83789 Iodine Concentration

82570 Creatinine Concentration

LOINC Code Information

Test ID Test Order Name Order LOINC Value
ICRU Iodine/Creat Ratio, Random, U In Process


Result ID Test Result Name Result LOINC Value
CDCR Creatinine Conc 2161-8
32874 Iodine/Creat Ratio, U 55928-6
32889 I Concentration 2495-0

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 <70 mcg/g creatinine suggest dietary deficiency.


Values >1,000 mcg/g creatinine 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

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

CDCR: Enzymatic Colorimetric Assay