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What is Mercury Blood test? 

Mercury is a toxic heavy metal that is present in various forms in the environment. It is also used in everyday products and produced by the combustion of fossil fuel.

Depending on its source and composition, mercury has three different forms:

  • Metallic mercury (present in dental fillings, batteries and thermometers)
  • Inorganic mercury (found in cosmetics such as skin lightening creams)
  • Organic mercury (such as methyl mercury, mostly found in seafood)

Mercury blood test is mainly performed to look for excessive amount of methyl mercury and other organic mercury compounds in the body.

Small amount of mercury is not harmful to health. However, acute exposure to high levels of mercury or long term and consistent exposure to small quantities of this heavy metal may lead to toxicity. Individuals who work in factories/industries which use this heavy metal are at a higher risk and tend to develop symptoms of mercury exposure over time. 

Additionally, smoke from factories, hospital incinerators and power plants can cause mercury exposure through inhalation. 

  1. Why is a Mercury Blood test performed?
  2. How do you prepare for a Mercury Blood test?
  3. How is a Mercury Blood test performed?
  4. What do Mercury Blood test results mean?

The primary aim of the mercury blood test is to measure the amount of mercury in your blood and determine the extent of exposure to this toxic metal. 

You will be asked to take this test in case you report symptoms of mercury poisoning. Organic mercury poisoning generally affects the brain and the nervous system. However, it may involve any system of the body including the gastrointestinal, respiratory, and immune system.

The most common signs and symptoms of mercury poisoning are as follows:

Prolonged exposure to mercury can produce the following symptoms:

  • Difficulty in walking
  • Loss of memory and brain fog
  • Vision problems 
  • Hearing problems
  • Problems with taste and smell
  • Tremors in the arms or legs

If a pregnant woman gets exposed to organic mercury (methyl mercury), it can damage the brain of the growing baby. 

Your doctor may also ask you to get tested for mercury levels if it is known that you have recently been exposed to the heavy metal (as in the case of individuals who work in industries and factories using heavy metals). Even if you are not showing any symptoms of toxicity, timely testing can help the doctor to determine the extent of mercury exposure.

No prior preparations are needed for this test. However, you must inform your doctor if you are taking any medications, health supplements or drugs. Also, let him/her know about your food habits and diet. Eating certain seafood that contains mercury could raise the mercury level in your blood. Tell your doctor if you use any skin lightening creams, as many of these contain mercury. 

Only a small amount of blood is needed to conduct this test. A doctor or laboratory technician will collect the required amount of blood sample from a vein in your arm using a sterile needle. 

You may experience slight pain as the needle goes in - it would subside soon after the test. 

Temporary lightheadedness and bruising are some common risks associated with a blood test. However, if you experience excessive discomfort check in with a doctor as soon as possible.

Normal results:

The reference value for this test is <5 ng/mL (nanograms/millilitre). It indicates that you do not have mercury toxicity.

Abnormal results:

Higher than normal levels of mercury in the blood may indicate mercury poisoning. High levels of mercury in the blood are usually interpreted as follows:

  • >5 ng/mL: Exposure to unhealthy levels of mercury through diet or occupational exposure
  • 30-40 ng/mL: Excessive exposure to mercury that can cause symptoms and lead to brain damage and kidney damage
  • >100 ng/mL: Mercury poisoning

Disclaimer: All results must be clinically correlated with the patient’s complaints to make a complete and accurate diagnosis. The above information is provided from a purely educational point of view and is in no way a substitute for medical advice by a qualified doctor.

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  1. World Health Organization [Internet]. Geneva (SUI): World Health Organization; Mercury and health
  2. United States Environment Protection Agency [internet]. Washington D.C. (U.S.A.). Health Effects of Exposures to Mercury
  3. Agency for Toxic Substances and Disease Registry [internet]. Center for Disease Control. Atlanta. GA. U.S. Mercury and Your health
  4. Sue YJ. Mercury. In: Hoffman RS, Howland MA, Lewin NA, Nelson LS, Goldfrank LR, eds. Goldfranks’s Toxicologic Emergencies. 10th edition. New York NY: McGraw-Hill Medical: chap 98.
  5. University of Rochester Medical Center [Internet]. Rochester (NY): University of Rochester Medical Center; Mercury (Blood)
  6. Risher JF et al. Organic mercury compounds: human exposure and its relevance to public health. Toxicol Ind Health. 2002 Apr;18(3):109-60. PMID: 12974562.