Mercury is a toxic heavy metal that can cause serious health effects when accumulated in the body. This test measures mercury levels in whole blood to monitor exposure and diagnose toxicity. Mercury exists in several forms: elemental (metallic), inorganic, and organic (methylmercury). Blood testing is most effective for detecting recent exposure to organic mercury compounds, which are commonly found in certain fish and seafood. Mercury toxicity can affect the nervous system, kidneys, and developing fetuses, with symptoms including tremors, memory problems, kidney damage, and developmental delays in children. This test is particularly important for monitoring occupational exposure in industries like mining and dentistry, evaluating dietary exposure from fish consumption, and assessing risk in pregnant women and children. Regular monitoring helps prevent chronic toxicity and guides appropriate interventions to reduce exposure.