Mercury (Hg)

This is a test to detect excessive exposure to mercury. It may be done if you have symptoms of mercury poisoning, to check a known exposure to mercury, or to monitor occupational exposure to mercury

This test measures the amount of mercury present in blood, urine, or (rarely) hair to detect acute or chronic excessive exposure. Mercury is an element that exists in three forms: as a free metal (liquid or vapor), an inorganic compound (mercury salt), and as a variety of organic compounds (the most common of which is methyl mercury).

Released by the breakdown of minerals in rocks and soils and through human activities, such as fossil fuel combustion and waste incineration, mercury is found in small amounts throughout the environment. It is inhaled with the air that we breathe, absorbed through the skin, and ingested with food. For the vast majority of people, the tiny amounts that they are exposed to do not cause any health problems.

The amount of mercury absorbed by an individual and its effect on their health depends on the type of mercury, its concentration, and the exposure time. For instance, according to the ATSDR (Agency for Toxic Substances and Disease Registry), 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 and about 95% of methyl mercury (the type found in fish and other seafood) is absorbed by the gastrointestinal tract. This is why it is so dangerous to eat fish caught in contaminated waters.

Once mercury is absorbed, it finds its way into a variety of body organs, including the kidney and brain. The body will slowly rid itself of mercury through the urine and stool, but if excessive amounts are present, they can damage the kidneys, nervous system, and brain. Pregnant women with elevated levels of mercury can pass it on to their fetus, affecting development as well as the fetus's brain, kidneys, and nerves. After birth, they can expose their nursing infant to mercury through their breast milk.


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.


Normal findings depend on many factors. Your lab will provide a range of normal findings with your test results.

Ranges for normal findings may vary among different laboratories and hospitals. You should always check with your doctor after having lab work or other tests done to discuss the meaning of your test results and whether your values are considered within normal limits.


Your caregiver will go over your test results with you and discuss the importance of this test. Reference values are dependent on many factors, including patient age, gender, sample population, and testing method. Numeric test results have different meanings in different labs.


It is your responsibility to obtain your test results. Ask the lab or department performing the test when and how you will get your results.