About the Test
Purpose of the test
Testing detects the presence of an excessive amount of mercury in your blood and/or urine sample. A health care practitioner may order testing to determine whether you had short-term (acute) exposure to a toxic level of mercury or have been exposed over an extended period of time (chronic exposure). Testing may also be used to monitor those who may be exposed to mercury in the workplace.
To test for the various forms of mercury, more than one type of sample may be collected and tested.
- Blood is primarily tested to detect methylmercury, the type found in fish and other seafood. Other forms of mercury (metallic and inorganic) can also be detected in the blood, but the amount present will decrease by half about every three days as the mercury moves into organs such as the brain and kidneys. Blood testing must be done within days of suspected exposure.
- Urine is used to test for metallic mercury and inorganic forms of mercury, but it cannot be used alone to determine exposure to dietary methylmercury.
- Hair testing may be useful to detect methylmercury exposures that occurred several months previously, but this type of testing is relatively complex and used infrequently.
- Although not routinely ordered tests, mercury has been shown to be present in nails, breast milk, stool, and breath.
Other general laboratory tests may be used to help evaluate the health of various organ systems in someone who has been exposed or thought to be exposed to toxic levels of mercury. Some examples include a comprehensive metabolic panel (CMP) and a complete blood count (CBC).
What does the test measure?
Mercury is an element that can be toxic in various forms, which are tested in different samples:
- Metallic or elemental mercury is a liquid often used in dental fillings, some thermometers, and batteries. Urine samples are typically tested to detect this form of mercury.
- Inorganic mercury salts, produced by the reaction of non-carbon based compounds with mercury, are normally in powder or crystal form. They are sometimes used in topical preparations such as skin-lightening or antiseptic creams. Urine samples are usually used to detect this form of mercury.
- Methylmercury and other organic mercury compounds are products of reactions between mercury and carbon-based organic compounds. Bacteria with elevated methylmercury levels are often in large, older predator fish such as sharks and king mackerel so eating those may expose you. Blood is primarily used to identify a high level of methylmercury.
The tiny amounts to which the vast majority of people are exposed do not generally cause health concerns. But you may develop mercury-related symptoms or complications if exposed to dangerous concentrations of mercury at a hazardous waste site or if you are exposed over long periods of time — especially when working with heavy metals.
Exposure to excessive amounts of mercury can be toxic. The amount of mercury you absorb and its effects on your health depend on the type of mercury, its concentration, and the nature of exposure.
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. But if the same mercury is inhaled as a vapor, about 80% is absorbed into the bloodstream.
About 95% of methylmercury is absorbed by the digestive tract. The most common source of human exposure to methylmercury is eating contaminated seafood. Fish from contaminated waters and large predator fish that have eaten smaller fish may have significantly increased levels of methylmercury. It is important to know the source of the fish that you consume and to limit the quantity of large predator fish eaten.
Once mercury is absorbed, the body may deposit it in a variety of 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 of the baby’s brain, kidneys, and nerves especially. Mercury can also be passed from mother to baby through breast milk during nursing.
When should I get this test?
Mercury testing may be ordered when you have signs and symptoms suggesting excessive exposure. Acute signs and symptoms may include:
- Burning in the mouth and lungs
- Cough, difficulty breathing, chest tightness
- Difficulty urinating and decreased urine output
- Nausea, vomiting, diarrhea, or abdominal cramping
- Increased heart rate
- Fever or chills
If you are chronically exposed you may have nonspecific symptoms that involve the lungs, kidneys, and nervous system. Some of these symptoms may include:
- Problems with hearing, taste and smell
- Blurry vision or sometimes tunnel vision
- Tingling or tremors in the arms or legs
- Difficulty walking
- Memory loss
To help evaluate the extent of the exposure, testing may also be ordered even in the absence of symptoms when it is known you have been exposed to mercury.
Mercury measurements may be ordered on a regular basis to monitor people who work in industries that use mercury. It may be ordered, along with tests to detect lead and/or other heavy metals, for individuals who work with a variety of potentially hazardous materials.
Finding a Mercury Test
How can I get a mercury test?
Mercury levels can be measured using a blood or urine test depending on the type of exposure. When testing for environmental mercury exposure, a blood test is usually performed in a doctor’s office, a hospital, or a laboratory.
Urine tests for mercury are used to screen for potential ingestion of mercury through diet or from medical exposure from dental amalgams. The amount of mercury released from dental amalgam fillings is insignificant, because it is generally way below the World Health Organization safety standard for daily mercury exposure.
Blood and urine tests are normally done after being prescribed by a doctor or other health professional. You can also order a blood mercury test or urine mercury test online.
Can I take the test at home?
You can take a mercury test at-home, either with a blood or urine sample. But you’ll need to visit a local laboratory to have your sample collected.
How much does the test cost?
The cost of a mercury test can change based on a number of factors including:
- Whether mercury is measured alone or as part of a panel test
- Whether the test uses a blood or urine sample
- Where the test sample is collected
- Whether your have health insurance coverage
The final cost of a mercury test can involve several components including charges for office visits, technician fees for taking your sample, and/or charges for laboratory evaluation.
Your insurance company may pay for some or all of these costs if your mercury test is prescribed by your doctor. For the most definitive information about likely costs, talk with your doctor’s office and medical insurance company.
Taking a Mercury Test
For mercury blood tests, a blood sample is taken in a medical lab, hospital, or doctor’s office. For a urine mercury test, you may provide a one-time sample at a medical office or lab.
Before the test
If you are having a blood or urine test for mercury, you may need to avoid seafood and red wine 72 hours prior to collection. Check with your doctor about whether you can eat and drink before the blood draw.
During the test
For a mercury blood test, a blood sample will be taken from a vein in your arm. Most of the time, an elastic band called a tourniquet will be tied around your upper arm. This increases blood flow in your arm and makes it easier to access the vein.
The technician will use an antiseptic wipe on your skin near the vein and then insert a needle. A vial of blood will be withdrawn, and then the needle will be taken out.
The total blood draw usually takes only a few minutes. There may be some pain during the procedure, and many people feel a brief sting when the needle is inserted.
For a urine test, you will be given a receptacle to collect urine in the bathroom at the doctor’s office or lab. Normally you will be instructed to start urinating into the toilet and then collect a sample by holding the receptacle under your stream of urine.
After the test
After a mercury blood test, a cotton swab or bandage will be placed over the puncture site to stop any bleeding. You can return to most normal activities once the test is over. Slight pain or bruising can affect your arm but normally goes away quickly.
There are few or no lasting effects from mercury urine tests. Once you have provided your urine sample, you can engage in daily activities without restrictions.
Mercury Test Results
Receiving test results
In most cases, results for both blood and urine mercury tests are available within a few business days.
Test results can be sent by mail or made accessible through online health portals. You may also receive a call or email from your doctor to either review your results or to schedule a follow-up appointment.
Interpreting test results
Levels of mercury in blood and urine are normally very low. A test result showing no mercury or a low level indicates that it is likely you have not been exposed to excessive levels of mercury, at least not in the window of time that the test is measuring.
An increased blood level suggests a relatively recent exposure to mercury. In general, a blood level greater than 10 microgram/liter (mcg/L) indicates an unusual level of exposure for someone who does not regularly work with mercury.
In contrast to levels of mercury in the blood, a 24-hour urine sample gives more of an average past history of exposure to metallic or inorganic mercury. Normal urine levels are typically less than 10 mcg/L for someone without risk of occupational exposure. An individual with urine mercury level 50 mcg/24-hr or higher often has symptoms of toxicity. (For information on occupational exposure levels, see the Related Tests section.)
Levels of mercury in either the blood or urine will not indicate the form or quantity of mercury to which you were exposed.
An increased level of mercury in hair testing may indicate exposure to increased levels of methylmercury, but hair samples are rarely used because of issues involving testing standardization and sample contamination. Also, hair is subject to many pre-analytical variables such as exposure to things like dyes, bleach, and shampoo.
Asking questions can help you understand the meaning of your mercury test results. When you talk with your doctor, some of these questions may be helpful to review:
- Was my mercury level low, normal, or high?
- Were any other measurements taken along with mercury? If so, were they normal or abnormal?
- If my mercury was too high or too low, what do you think is the most likely cause?
- Are there any follow-up tests that you recommend?
- Should I have another mercury test?
- What can I do to reduce my exposure to mercury?