Test Id : IODCU
Iodine/Creatinine Ratio, Random, Urine
Useful For
Suggests clinical disorders or settings where the test may be helpful
Assessment of iodine toxicity or recent iodine exposure using a random urine collection
Monitoring iodine excretion rate as index of replacement therapy
Profile Information
A profile is a group of laboratory tests that are ordered and performed together under a single Mayo Test ID. Profile information lists the test performed, inclusive of the test fee, when a profile is ordered and includes reporting names and individual availability.
| Test Id | Reporting Name | Available Separately | Always Performed |
|---|---|---|---|
| IODC | Iodine/Creat Ratio, U | No | Yes |
| CRETR | Creatinine, Random, U | No | Yes |
Method Name
A short description of the method used to perform the test
IODC: Inductively Coupled Plasma Mass Spectrometry (ICP-MS)
CRETR: Enzymatic Colorimetric Assay
NY State Available
Indicates the status of NY State approval and if the test is orderable for NY State clients.
Reporting Name
Lists a shorter or abbreviated version of the Published Name for a test
Aliases
Lists additional common names for a test, as an aid in searching
Iodine Excretion
Urinary Free Iodine
Urinary Iodine
IODCU
Specimen Type
Describes the specimen type validated for testing
Urine
Ordering Guidance
Due to the significant variation in the rate of excretion over the course of a day, a 24-hour collection is preferred. For more information see UIOD / Iodine, 24 Hour, Urine.
Specimen Required
Defines the optimal specimen required to perform the test and the preferred volume to complete testing
Patient Preparation: High concentrations of gadolinium and iodine may interfere with inductively coupled plasma mass spectrometry-based metal tests. If either gadolinium- or iodine-containing contrast media has been administered, the specimen should not be collected for at least 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 Metals Analysis Specimen Collection and Transport for complete instructions.
Special Instructions
Library of PDFs including pertinent information and forms related to the test
Specimen Minimum Volume
Defines the amount of sample necessary to provide a clinically relevant result as determined by the testing laboratory. The minimum volume is sufficient for one attempt at testing.
2 mL
Reject Due To
Identifies specimen types and conditions that may cause the specimen to be rejected
Specimen Stability Information
Provides a description of the temperatures required to transport a specimen to the performing laboratory, alternate acceptable temperatures are also included
| Specimen Type | Temperature | Time | Special Container |
|---|---|---|---|
| Urine | Refrigerated (preferred) | 30 days | |
| Ambient | 14 days | ||
| Frozen | 30 days |
Useful For
Suggests clinical disorders or settings where the test may be helpful
Assessment of iodine toxicity or recent iodine exposure using a random urine collection
Monitoring iodine excretion rate as index of replacement therapy
Clinical Information
Discusses physiology, pathophysiology, and general clinical aspects, as they relate to a laboratory test
Iodine is an essential element for thyroid hormone production.
The measurement of urinary iodine is preferred for assessment of toxicity, recent exposure, and monitoring iodine excretion rate as an index of replacement therapy.
Reference Values
Describes reference intervals and additional information for interpretation of test results. May include intervals based on age and sex when appropriate. Intervals are Mayo-derived, unless otherwise designated. If an interpretive report is provided, the reference value field will state this.
0-17 years: Not established
> or =18 years: <584 mcg/g creatinine
Interpretation
Provides information to assist in interpretation of the test results
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.
World Healthcare Organization (WHO) Criteria for Assessing Iodine Status
Children older than 6 years and adults
| Median urinary iodine (mcg/L) | Iodine intake | Iodine status |
| <20 | Insufficient | Severe deficiency |
| 20-49 | Insufficient | Moderate deficiency |
| 50-99 | Insufficient | Mild deficiency |
| 100-199 | Adequate | Adequate nutrition |
| 200-299 | Above requirements | May pose a slight risk of more than adequate |
| >299 | Excessive | Risk of adverse health consequences |
Pregnant women
| Median urinary iodine (mcg/L) | Iodine intake |
| <150 | Insufficient |
| 150-249 | Adequate |
| 250-499 | Above requirements |
| >499 | Excessive |
Lactating women and children younger than 2 years
| Median urinary iodine (mcg/L) | Iodine intake |
| <100 | Insufficient |
| >99 | Adequate |
Cautions
Discusses conditions that may cause diagnostic confusion, including improper specimen collection and handling, inappropriate test selection, and interfering substances
Administration of iodine-based contrast media and drugs containing iodine, such as amiodarone, will yield elevated results.
Clinical Reference
Recommendations for in-depth reading of a clinical nature
1. Rifai N, Chiu RWK, Young I, Burnham CAD, Wittwer CT, eds. Tietz Textbook of Laboratory Medicine. 7th ed. Elsevier; 2023
2. Knudsen N, Christiansen E, Brandt-Christensen M, Nygaard B, Perrild H. 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(4):361-363
3. Liberman CS, Pino SC, Fang SL, Braverman LE, Emerson CH. Circulating iodide concentrations during and after pregnancy. J Clin Endocrinol Metab. 1998;83(10):3545-3549
4. Pfeiffer CM, Sternberg MR, Schleicher RL, Haynes BM, Rybak ME, Pirkle JL. The CDC's Second National Report on Biochemical Indicators of Diet and Nutrition in the U.S. Population is a valuable tool for researchers and policy makers. J Nutr. 2013;143(6):938S-947S
5. U.S. Department of Health and Human Services, Agency for Toxic Substances and Disease Registry: Toxicological Profile for Iodine. HHS; 2004. Accessed March 21, 2025. Available at www.atsdr.cdc.gov/ToxProfiles/tp158.pdf
6. Leung AM, Braverman LE. Consequences of excess iodine. Nat Rev Endocrinol. 2014;10(3):136-142. doi:10.1038/nrendo.2013.251
7. Beckford K, Grimes CA, Margerison C, et al. A systematic review and meta-analysis of 24-h urinary output of children and adolescents: impact on the assessment of iodine status using urinary biomarkers. Eur J Nutr. 2020;59(7):3113-3131. doi:10.1007/s00394-019-02151-w
Method Description
Describes how the test is performed and provides a method-specific reference
The metal of interest is analyzed by inductively coupled plasma mass spectrometry.(Unpublished Mayo method)
PDF Report
Indicates whether the report includes an additional document with charts, images or other enriched information
Day(s) Performed
Outlines the days the test is performed. This field reflects the day that the sample must be in the testing laboratory to begin the testing process and includes any specimen preparation and processing time before the test is performed. Some tests are listed as continuously performed, which means that assays are performed multiple times during the day.
Tuesday, Friday
Report Available
The interval of time (receipt of sample at Mayo Clinic Laboratories to results available) taking into account standard setup days and weekends. The first day is the time that it typically takes for a result to be available. The last day is the time it might take, accounting for any necessary repeated testing.
Specimen Retention Time
Outlines the length of time after testing that a specimen is kept in the laboratory before it is discarded
Performing Laboratory Location
Indicates the location of the laboratory that performs the test
Fees :
Several factors determine the fee charged to perform a test. Contact your U.S. or International Regional Manager for information about establishing a fee schedule or to learn more about resources to optimize test selection.
- Authorized users can sign in to Test Prices for detailed fee information.
- Clients without access to Test Prices can contact Customer Service 24 hours a day, seven days a week.
- Prospective clients should contact their account representative. For assistance, contact Customer Service.
Test Classification
Provides information regarding the medical device classification for laboratory test kits and reagents. Tests may be classified as cleared or approved by the US Food and Drug Administration (FDA) and used per manufacturer instructions, or as products that do not undergo full FDA review and approval, and are then labeled as an Analyte Specific Reagent (ASR) product.
This test was developed and its performance characteristics determined by Mayo Clinic in a manner consistent with CLIA requirements. It has not been cleared or approved by the US Food and Drug Administration.
CPT Code Information
Provides guidance in determining the appropriate Current Procedural Terminology (CPT) code(s) information for each test or profile. The listed CPT codes reflect Mayo Clinic Laboratories interpretation of CPT coding requirements. It is the responsibility of each laboratory to determine correct CPT codes to use for billing.
CPT codes are provided by the performing laboratory.
CPT codes are provided by the performing laboratory.
83789
82570
LOINC® Information
Provides guidance in determining the Logical Observation Identifiers Names and Codes (LOINC) values for the order and results codes of this test. LOINC values are provided by the performing laboratory.
| Test Id | Test Order Name | Order LOINC Value |
|---|---|---|
| IODCU | Iodine/Creat Ratio, Random, U | 55928-6 |
| Result Id | Test Result Name |
Result LOINC Value
Applies only to results expressed in units of measure originally reported by the performing laboratory. These values do not apply to results that are converted to other units of measure.
|
|---|---|---|
| CRETR | Creatinine, Random, U | 2161-8 |
| 610709 | Iodine/Creat Ratio, U | 55928-6 |
| 614424 | Iodine Concentration Interpretation | 77202-0 |
| 614370 | Iodine Concentration | 2495-0 |