Also Known As
LDH
This article was last reviewed on
This article waslast modified on October 12, 2018.
At a Glance
Why Get Tested?

To help detect a condition causing tissue damage, such as a blood or liver disease, and to monitor its progress; to help stage, determine prognosis, and/or response to treatment of certain cancers; to help evaluate body fluid (other than blood)

When To Get Tested?

Along with other tests, when a healthcare practitioner suspects that you have an acute or chronic condition that is causing tissue damage or cellular destruction; sometimes when you have been diagnosed with cancer; when you have symptoms of meningitis or have fluid accumulation in a specific part of your body

Sample Required?

A blood sample is obtained by inserting a needle into a vein in the arm. Sometimes a special procedure may be performed to collect body fluid from the site affected (e.g., cerebrospinal fluidpleural fluidperitoneal fluid, etc.).

Test Preparation Needed?

None

You may be able to find your test results on your laboratory's website or patient portal. However, you are currently at Lab Tests Online. You may have been directed here by your lab's website in order to provide you with background information about the test(s) you had performed. You will need to return to your lab's website or portal, or contact your healthcare practitioner in order to obtain your test results.

Lab Tests Online is an award-winning patient education website offering information on laboratory tests. The content on the site, which has been reviewed by laboratory scientists and other medical professionals, provides general explanations of what results might mean for each test listed on the site, such as what a high or low value might suggest to your healthcare practitioner about your health or medical condition.

The reference ranges for your tests can be found on your laboratory report. They are typically found to the right of your results.

If you do not have your lab report, consult your healthcare provider or the laboratory that performed the test(s) to obtain the reference range.

Laboratory test results are not meaningful by themselves. Their meaning comes from comparison to reference ranges. Reference ranges are the values expected for a healthy person. They are sometimes called "normal" values. By comparing your test results with reference values, you and your healthcare provider can see if any of your test results fall outside the range of expected values. Values that are outside expected ranges can provide clues to help identify possible conditions or diseases.

While accuracy of laboratory testing has significantly evolved over the past few decades, some lab-to-lab variability can occur due to differences in testing equipment, chemical reagents, and techniques. This is a reason why so few reference ranges are provided on this site. It is important to know that you must use the range supplied by the laboratory that performed your test to evaluate whether your results are "within normal limits."

For more information, please read the article Reference Ranges and What They Mean.

What is being tested?

Lactate dehydrogenase (LD or LDH) is an enzyme involved in energy production that is found in almost all of the body's cells, with the highest levels found in the cells of the heart, liver, muscles, kidneys, lungs, and in blood cells; bacteria also produce LD. This test measures the level of LD in the blood or sometimes other body fluids.

Blood LD
Only a small amount of LD is usually detectable in the fluid portion of the blood (serum or plasma). LD is released from the cells into the serum when cells are damaged or destroyed. Thus, an LD blood level is a non-specific marker for the presence of tissue damage somewhere in the body. By itself, it cannot be used to identify the underlying cause or location of the cellular damage. However, it may be used, in conjunction with other blood tests, to help evaluate for and/or monitor conditions that lead to tissue damage, such as liver or blood diseases or cancer.

Fluid LD
Sometimes when there is injury, inflammation, or infection within a specific area of the body, such as the brain, heart or lungs, fluid will accumulate or constituents of the fluid present will change. The level of LD present in the fluid may be useful in determining the cause. For example, LD is typically high in cerebrospinal fluid when an individual has bacterial meningitis. The LD test can also be used, along with other tests, to determine whether fluid accumulation, for example around the heart or lungs or in the abdominal cavity, is due to injury or inflammation (exudate) or due to an imbalance of fluid pressure inside blood vessels and the protein level in blood (transudate). The article on Body Fluid Analysis lists some fluids that may be evaluated using an LD test.

Accordion Title
Common Questions
  • How is the test used?

    A lactate dehydrogenase (LD or LDH) test is a non-specific test that may be used in the evaluation of a number of diseases and conditions.

    An LD blood test may be used:

    An LD test is performed on body fluids for a few different reasons:

    • To help evaluate cerebrospinal fluid and distinguish between bacterial or viral meningitis
    • To evaluate other body fluids such as pleural, peritoneal or pericardial fluid and help determine whether the accumulation of fluid is due to injury and inflammation (exudate) or due to an imbalance of pressure within blood vessels and the amount of protein in the blood (transudate). This information is helpful in guiding treatment.

    The article on Body Fluid Analysis lists some fluids other than blood that may be evaluated with an LD test.

  • When is it ordered?

    Blood test
    An LD level may be ordered, along with other tests such as a comprehensive metabolic panel (CMP), when a healthcare practitioner suspects that a disease or condition is causing some degree of cellular or tissue damage. If LD is elevated, then more specific tests, such as ALT, AST or ALP, may help diagnose the condition and help determine which organs are involved. Once the acute or chronic problem is diagnosed, total LD levels may be ordered at regular intervals to monitor its progress and/or resolution.

    LD levels may also occasionally be ordered when an individual has experienced muscle trauma or injury or when a person has signs and symptoms of hemolytic anemia.

    LD testing may be ordered on a regular basis when an individual has been diagnosed with cancer.

    Body fluid test
    This test may be ordered, for example, when a person has signs and symptoms of meningitis or when someone has a buildup of fluid around the heart, lungs or in the abdomen.

  • What does the test result mean?

    Blood test
    Elevated levels of LD usually indicate some type of tissue damage. LD levels typically will rise as the cellular destruction begins, peak after some time period, and then begin to fall. LD levels are elevated in a wide variety of conditions, reflecting its widespread tissue distribution.

    An elevated level of LD may be seen with:

    A high LD in the blood may indicate that treatment for cancer (e.g., chemotherapy) has not been successful. A high level is predictive of a poorer outlook for survival for those with cancer.

    With some chronic and progressive conditions, moderately elevated LD blood levels may persist.

    Low and normal levels of LD do not usually indicate a problem. Low levels are sometimes seen when someone ingests large amounts of ascorbic acid (vitamin C).

    Body fluids:

    • Cerebrospinal fluid—a high LD indicates that meningitis is likely caused by bacteria, while a low or normal level indicates viral meningitis is more likely.
    • A high LD indicates that pericardial fluid, peritoneal or pleural fluid is an exudate, while a low level indicates it is transudate. Transudates are usually caused by congestive heart failure or cirrhosis. Exudates have several possible causes and usually require additional testing to determine the cause. Read more about these tests by accessing the specific fluid article listed under Related Content (below).
  • Is there anything else I should know?

    Many things can affect LD results that are not necessarily a cause for concern. For example:

    • Strenuous exercise can cause temporary elevations in LD.
    • Hemolysis of the blood specimen can cause falsely elevated results. This may happen if the specimen is handled roughly, stored in extreme temperatures, or if the sample was difficult to collect.
    • If a person's platelet count is increased, serum LD can be artificially high and not reflective of the LD actually present in the circulation.
  • If the LD test is not specific, how can it be clinically useful?

    The LD test can be useful because it can alert a healthcare practitioner that cellular injury is occurring. In a similar fashion, tests such as a C-reactive protein (CRP) warn that inflammation is occurring somewhere in the body.

  • Is there anything I can do to lower my LD?

    No, it is an indicator of injury that will typically return to normal when the underlying condition resolves. If someone has a chronic condition with ongoing tissue damage, such as may occur with liver disease, then increased LD concentrations may persist.

  • What is an LD isoenzymes test?

    A test for LD isoenzymes is rarely ordered and not widely available nowadays. In the past, the test was used to help diagnose and monitor heart attacks, but it has been replaced by the test for troponin. Though not a routine test, it may be used in differential diagnosis to help determine which organs are likely affected by tissue damage when the cause of an elevated total LD is not clear and cannot be determined using other specific tests.

    LD exists in five different forms called isoenzymes. Although there is some overlap, each of the five LD isoenzymes tends to be concentrated in specific body tissues. In general, the isoenzyme locations tend to be:

    • LD-1: heart, red cells, kidneys, germ cells
    • LD-2: kidneys, red blood cells, lungs, heart (lesser amounts than LD-1)
    • LD-3: lungs and other tissues
    • LD-4: white blood cells, lymph nodes, muscles, liver (lesser amounts than LD-5)
    • LD-5: liver, skeletal muscle

    Determining which isoenzyme is elevated in the blood may give clues to where tissue damage is occurring in the body and/or which organs may be affected.

View Sources

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Lactate Dehydrogenase (LD), Body Fluid. Mayo Medical Laboratories. Available online at https://www.mayomedicallaboratories.com/test-catalog/Clinical+and+Interpretive/8022. Accessed on June 13, 2018.

Lactic Acid Dehydrogenase (Blood). University of Rochester Medical Center. Available online at https://www.urmc.rochester.edu/encyclopedia/content.aspx?contenttypeid=167&contentid=lactic_acid_dehydrogenase_blood. Accessed on 6/13/18.

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