Assessing iodine toxicity or recent exposure in a 24-hour urine collection
Monitoring iodine excretion rate as index of replacement therapy
Inductively Coupled Plasma Mass Spectrometry (ICP-MS)
Urinary Free Iodine
Urinary Iodine
Urine
24-Hour volume (in milliliters) is required.
Question ID | Description | Answers |
---|---|---|
TIME5 | Collection Duration (h) | |
VL23 | Volume (mL) |
Patient Preparation:
1. High concentrations of gadolinium and iodine are known to potentially interfere with most inductively coupled plasma mass spectrometry-based metal tests. If either 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)
Collection Container/Tube: Clean, plastic aliquot container with no metal cap or glued insert
Submission Container/Tube: Plastic, 10-mL urine tube
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 Metals Analysis Specimen Collection and Transport for complete instructions.
Additional Information: See Urine Preservatives-Collection and Transportation for 24-Hour Urine Specimens for multiple collections.
Note: The addition of preservative or application of temperature controls must occur within 4 hours of completion of the collection.
Ambient (no additive) | OK |
Refrigerate (no additive) | Preferred |
Frozen (no additive) | OK |
50% Acetic Acid | OK |
Boric Acid | No |
Diazolidinyl Urea | No |
6M Hydrochloric Acid | No |
6M Nitric Acid | No |
Sodium Carbonate | No |
Thymol | No |
Toluene | No |
0.3 mL
Specimen Type | Temperature | Time | Special Container |
---|---|---|---|
Urine | Ambient | 146 days | |
Refrigerated (preferred) | 146 days | ||
Frozen | 146 days |
Assessing iodine toxicity or recent exposure in a 24-hour urine collection
Monitoring iodine excretion rate as index of replacement therapy
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.
0-17 years: Not established
> or =18 years: 75-851 mcg/24 hour
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.
World Healthcare Organization (WHO) Criteria for Assessing Iodine Status
Children older than 6 years and adults(1)
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(1)
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(1)
Median urinary iodine (mcg/L) | Iodine intake |
<100 | Insufficient |
>99 | Adequate |
Administration of iodine-based contrast media and drugs containing
1. Department of Nutrition for Health and Development (NHD); World Health Organization. Urinary iodine concentrations for determining iodine status in populations. World Health Organization; 2013. Accessed April 25, 2025. Available at www.who.int/publications/i/item/WHO-NMH-NHD-EPG-13.1
2. Rifai N, Chiu RWK, Young I, Burnham CAD, Wittwer CT, eds. Tietz Textbook of Laboratory Medicine. 7th ed. Elsevier; 2023
3. 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(4):361-363
4. Liberman CS, Pino SC, Fang SL, et al. Circulating iodine concentrations during and after pregnancy. J Clin Endocrinol Metab. 1998;83(10):3545-3549
5. 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
6. Leung AM, Braverman LE. Consequences of excess iodine. Nat Rev Endocrinol. 2014;10(3):136-142. doi:10.1038/nrendo.2013.251
7. U.S. Department of Health and Human Services, Agency for Toxic Substances and Disease Registry: Toxicological Profile for Iodine. HHS, 2004. Accessed April 25, 2025. Available at www.atsdr.cdc.gov/ToxProfiles/tp158.pdf
The metal of interest is analyzed by inductively coupled plasma mass spectrometry.(Unpublished Mayo method)
Tuesday, Friday
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.
83789
Test Id | Test Order Name | Order LOINC Value |
---|---|---|
UIOD | Iodine, 24 Hr, U | 2492-7 |
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.
|
---|---|---|
9549 | Iodine, 24 Hr, U | 2492-7 |
TIME5 | Collection Duration (h) | 13362-9 |
VL23 | Volume (mL) | 3167-4 |
614369 | Iodine Concentration | 26842-5 |
614423 | Iodine Concentration Interpretation | 77202-0 |
Change Type | Effective Date |
---|---|
File Definition - Result ID | 2025-04-22 |