Test Catalog

Test ID: CRCRU    
Chromium/Creatinine Ratio, Random, Urine

Useful For Suggests clinical disorders or settings where the test may be helpful

Detecting chromium exposure

Clinical Information Discusses physiology, pathophysiology, and general clinical aspects, as they relate to a laboratory test

Chromium (Cr) has an atomic mass of 51.996, atomic number 24, and valences ranging from 2(-) to 6(+). Hexavalent chromium, Cr(6+), and trivalent chromium, Cr(3+), are the 2 most prevalent forms. Cr(3+) is the only oxidation state present under normal physiologic conditions. Cr(6+) is widely used in industry to make chromium alloys including stainless steel pigments and electroplated coatings. Cr(6+), a known carcinogen, is rapidly metabolized to Cr(3+). Cr(3+) is the only form present in human urine.

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

>17 years: <0.8 mcg/g Creatinine

Interpretation Provides information to assist in interpretation of the test results

Chromium is principally excreted in the urine. Results greater than the reference range indicate either recent exposure to chromium or specimen contamination during collection.


The National Institute for Occupational Safety and Health (NIOSH) document on occupational exposure reviews the data supporting use of urine to assess chromium exposure. The biological exposure indices (BEI) for total chromium in urine measured at the end of the shift at the end of the workweek is 25 mcg/L. The BEI for the increase in total chromium during a shift is 10 mcg/L. A test for this specific purpose (CROMU / Chromium for Occupational Monitoring, Random, Urine) is available.

Cautions Discusses conditions that may cause diagnostic confusion, including improper specimen collection and handling, inappropriate test selection, and interfering substances

Normal specimens have extremely low levels of creatinine; elevated results could easily be a result of external contamination. Precautions must be taken to ensure the specimen is not contaminated. Metal-free urine collection procedures must be followed. Refrigeration is preferred over chemical methods of preservation.


Specimen collection procedures for chromium require special specimen collection tubes, rigorous attention to ultraclean specimen collection and handling procedures, and analysis in an ultraclean facility. Unless all of these precautions are taken, elevated urine chromium results may be an incidental and misleading finding.

Clinical Reference Recommendations for in-depth reading of a clinical nature

1. U.S. Department of Health and Human Services, Agency for Toxic Substances and Disease Registry. Toxicology profile for chromium. September 2012. Accessed 11/06/2020. Available at www.atsdr.cdc.gov/ToxProfiles/tp7.pdf

2. Rifai N, Horwath AR, Wittwer CT, eds: Tietz Textbook of Clinical Chemistry and Molecular Diagnostics. 6th ed. Elsevier; 2017

3. Centers for Disease Control and Prevention: National Institute for Occupational Safety and Health (NIOSH) criteria for a recommended standard occupational exposure to hexavalent chromium. September 2013. Accessed 11/06/2020. Available at www.cdc.gov/niosh/docs/2013-128/pdfs/2013_128.pdf

4. Gianello G, Masci O, Carelli G, Vinci F, Castellino N: Occupational exposure to chromium-an assessment of environmental pollution levels and biological monitoring of exposed workers. Ind Health. 1998 Jan;36(1):74-77. doi: 10.2486/indhealth.36.74.

Special Instructions Library of PDFs including pertinent information and forms related to the test