Mercury

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Also known as: Hg
Formal name: Mercury, Urine and Blood
Related tests: Lead, Arsenic, Heavy Metals

At a Glance

Why Get Tested?

To detect excessive exposure to mercury

When to Get Tested?

When you have symptoms of mercury poisoning, to evaluate a known exposure to mercury, or to monitor occupational exposure to mercury

Sample Required?

A blood sample drawn from a vein in your arm and/or a urine collection

Test Preparation Needed?

None

The Test Sample

What is being tested?

Mercury is an element that exists in three forms:

  • Metallic or elemental mercury (liquid or vapor) is often used in dental fillings, some thermometers, and batteries.
  • Mercury can combine with other elements such as oxygen or sulfur to form an inorganic compound (mercury salt). In this form, it appears as a powder or crystal and is sometimes used in topical preparations such as skin-lightening or antiseptic creams. 
  • When mercury combines with carbon, it can form a variety of organic compounds, the most common of which is methyl mercury. This form is produced by bacteria found in soil and water. Elevated levels are often found in large, older, predator fish such as sharks and king mackerel. 

This test measures the amount of mercury present in blood, urine, or (rarely) hair to detect acute or chronic excessive exposure.

Mercury is found in small quantities throughout the environment. It is released by the breakdown of minerals in rocks and soils and as a byproduct of fossil fuel combustion and waste incineration. It is inhaled with the air that we breathe, absorbed through the skin, and ingested with food. The tiny amounts to which the vast majority of people are exposed do not generally cause health concerns. However, people who are exposed to dangerous concentrations of mercury, such as might be found at a hazardous waste site, and people who are exposed chronically to mercury over long periods of time, such as those who work with heavy metals in their occupation, may have mercury-related symptoms and complications.

Exposure to excessive amounts of mercury can be toxic. The amount of mercury absorbed by an individual and its effects on their health depends on the type of mercury, its concentration, and the exposure time. According to the Agency for Toxic Substances and Disease Registry (ATSDR), very little metallic mercury (less than 0.01%) is absorbed by the body, even if it is swallowed. However, if the same mercury is inhaled as a vapor, about 80% is absorbed into the bloodstream.

About 95% of methyl mercury, which is the type found in fish and other seafood, is absorbed by the digestive tract. The most common source of human exposure to methyl mercury is as a result of eating contaminated seafood. Fish that come from contaminated waters and larger, predator fish fish that have eaten smaller fish may have significantly increased levels of methyl mercury. This is why it is recommended that you know the source of the fish you consume and that you limit the quantity of large predator fish you eat.

Once mercury is absorbed, it can be deposited in a variety of body organs, including the kidneys and brain. The body will slowly rid itself of mercury through the urine and stool, but if an excessive amount accumulates, it can permanently damage the kidneys, nervous system, and brain.

Pregnant women with elevated levels of mercury can pass it on to their unborn baby, affecting development, especially the baby's brain, kidneys, and nerves. Mercury can also be passed from mother to baby through breast milk during nursing.

How is the sample collected for testing?

A blood sample is obtained by inserting a needle into a vein in the arm or a random or 24 hour urine sample may be collected. Rarely, another sample such as hair, breast milk, or nails may be tested.

NOTE: If undergoing medical tests makes you or someone you care for anxious, embarrassed, or even difficult to manage, you might consider reading one or more of the following articles: Coping with Test Pain, Discomfort, and Anxiety, Tips on Blood Testing, Tips to Help Children through Their Medical Tests, and Tips to Help the Elderly through Their Medical Tests.

Another article, Follow That Sample, provides a glimpse at the collection and processing of a blood sample and throat culture.

Is any test preparation needed to ensure the quality of the sample?

No test preparation is needed. Consult your doctor or laboratory about urine collection to avoid sample contamination.

The Test

Common Questions

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Article Sources

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NOTE: This article is based on research that utilizes the sources cited here as well as the collective experience of the Lab Tests Online Editorial Review Board. This article is periodically reviewed by the Editorial Board and may be updated as a result of the review. Any new sources cited will be added to the list and distinguished from the original sources used.

Sources Used in Current Review

(Updated September 3, 2010) Department of Health and Human Services, The Center for the Evaluation of Risks to Human Reproduction. Mercury. Available online at http://cerhr.niehs.nih.gov/common/mercury.html through http://cerhr.niehs.nih.gov. Accessed May 2011.

(Updated March 3, 2011) Agency for Toxic Substances and Disease Registry. Public Health Statement for Mercury. Available online at http://www.atsdr.cdc.gov/phs/phs.asp?id=112&tid=24 through http://www.atsdr.cdc.gov. Accessed May 2011.

(February 2009) Agency for Toxic Substance and Disease Registry. Evaluating for Mercury Exposure: Information for Health Care Providers. PDF available for download at http://www.atsdr.cdc.gov/mercury/docs/Physician_Hg_Flier.pdf through http://www.atsdr.cdc.gov. Accessed May 2011.

(Updated September 21, 2009) Olsen D. Mercury. Medscape article. Available online at http://emedicine.medscape.com/article/1175560-overview through http://emedicine.medscape.com. Accessed May 2011.

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(Updated June 30, 2010) Tan D. Pediatric Mercury Toxicity. eMedicine article. Available online at http://emedicine.medscape.com/article/1009691-overview through http://emedicine.medscape.com. Accessed May 2011.

(February 2, 2009) MedlinePlus Medical Encyclopedia. Mercury. Available online at http://www.nlm.nih.gov/medlineplus/ency/article/002476.htm. Accessed May 2011.

Tietz Textbook of Clinical Chemistry and Molecular Diagnostics. Burtis CA, Ashwood ER, Bruns DE, eds. St. Louis: Elsevier Saunders; 2006, Pp1381-1382.

(December 9, 2009) National Institute of Allergy and Infectious Diseases. Vaccines, Thimerosal in vaccines. Available online at http://www.niaid.nih.gov/topics/vaccines/research/Pages/vaccines.aspx through http://www.niaid.nih.gov. Accessed May 2011.

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Pagana, Kathleen D. & Pagana, Timothy J. (2001). Mosby's Diagnostic and Laboratory Test Reference 5th Edition: Mosby, Inc., Saint Louis, MO.

(2004 August 02, Updated). Public Health Statement for Mercury. Agency for Toxic Substances and Disease Registry (ATSDR) [On-line information]. Available online at http://www.atsdr.cdc.gov/toxprofiles/phs46.html through http://www.atsdr.cdc.gov.

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