Lactate Dehydrogenase and Isoenzymes

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Lactate Dehydrogenase and Isoenzymes

Synonym/acronym: LDH and isos, LD, and isos.

Common use

To assess myocardial or skeletal muscle damage toward diagnosing disorders such as myocardial infarction or damage to brain, liver, kidneys, and skeletal muscle.


Serum (1 mL) collected in a gold-, red-, or red/gray-top tube.

Normal findings

(Method: Enzymatic [L to P] for lactate dehydrogenase, electrophoretic analysis for isoenzymes) Reference ranges are method dependent and may vary among laboratories. Lactate Dehydrogenase
AgeConventional & SI Units
0–2 yr125–275 units/L
2–3 yr166–232 units/L
4–6 yr104–206 units/L
7–12 yr90–203 units/L
13–14 yr90–199 units/L
15–43 yr90–156 units/L
Greater than 43 yr90–176 units/L
LDH Fraction% of TotalFraction of Total


Lactate dehydrogenase (LDH) is an enzyme that catalyzes the reversible conversion of lactate to pyruvate within numerous tissues in the body, making it a nonspecific indicator of cellular damage. Determining tissue origin can be accomplished by electrophoretic analysis of the five isoenzymes found in certain tissues. The heart and erythrocytes are rich sources of LDH1, LDH2, and LDH3; the kidneys contain large amounts of LDH3 and LDH4; and the liver and skeletal muscles are high in LDH4and LDH5. Certain glands (e.g., thyroid, adrenal, thymus), the pancreas, spleen, lungs, lymph nodes, and white blood cells contain LDH3, whereas the ilium is an additional source of LDH5. Documented reports identify a sixth isoenzyme of LDH. It is seen in patients with severe liver disease and is an indicator of a very poor prognosis. Testing for the presence of LDH and isoenzymes is rarely used anymore to confirm acute myocardial infarction (MI), having been replaced by more sensitive and specific creatine kinase (CK-MB) and troponin assays. Acute MI releases LDH into the serum within the first 12 hr, causing a “flip” isoenzyme pattern within 48 hr of MI, and levels remain elevated for 1 to 2 wk after CK and aspartate aminotransferase have returned to normal levels.

This procedure is contraindicated for



  • Differentiate acute MI from pulmonary infarction and liver problems (acute MI elevates LDH1 and LDH2 levels; pulmonary infarction and liver problems elevate LDH4 and LDH5)
  • Evaluate the degree of muscle wasting in muscular dystrophy (LDH levels rise early in this disorder and approach normal as muscle mass is reduced by atrophy)
  • Evaluate red cell hemolysis or renal infarction, especially as indicated by reversal of the LDH1:LDH2 ratio
  • Investigate acute MI or extension thereof (indicated by elevation [usually] of total LDH, elevation of LDH1 and LDH2, and reversal of the LDH1:LDH2 ratio within 48 hr of the infarction)
  • Investigate chronicity of liver, lung, and kidney disorders (evidenced by LDH levels that remain persistently high)

Potential diagnosis

Total LDH Increased In

LDH is released from any damaged cell in which it is stored so conditions that affect the heart, liver, kidneys, red blood cells, skeletal muscle, or other tissue source and cause cellular destruction demonstrate elevated LDH levels.

Carcinoma of the liver Chronic alcoholism Cirrhosis Congestive heart failure Hemolytic anemias Hypoxia Leukemias Megaloblastic and pernicious anemia MI or pulmonary infarction Musculoskeletal disease Obstructive jaundice Pancreatitis Renal disease (severe) Shock Viral hepatitis

Total LDH Decreased In:

  • LDH Isoenzymes
  • LDH1 fraction increased over LDH2 can be seen in acute MI, anemias (pernicious, hemolytic, acute sickle cell, megaloblastic, hemolytic), and acute renal cortical injury due to any cause. The LDH1 fraction in particular is elevated in cases of germ cell tumors. Increases in the middle fractions are associated with conditions in which massive platelet destruction has occurred (e.g., pulmonary embolism, post-transfusion period) and in lymphatic system disorders (e.g., infectious mononucleosis, lymphomas, lymphocytic leukemias). An increase in LDH5 occurs with musculoskeletal damage and many types of liver damage (e.g., cirrhosis, cancer, hepatitis).

    Critical findings


    Interfering factors

    • Drugs that may increase total LDH levels include amiodarone, etretinate, Fluosol-DA, methotrexate, oxacillin, plicamycin, propoxyphene, and streptokinase.
    • Drugs that may decrease total LDH levels include ascorbic acid, cefotaxime, enalapril, fluorides, naltrexone, and oxylate.
    • Hemolysis will cause significant false elevations in total LDH and a false “flip” pattern of the isoenzymes because LDH1 fraction is of red blood cell origin.
    • Some isoenzymes are temperature sensitive; therefore, prolonged storage at refrigerated temperatures may cause false decreases.

    Nursing Implications and Procedure


    • Positively identify the patient using at least two unique identifiers before providing care, treatment, or services.
    • Patient Teaching:  Inform the patient this test can assist in evaluating muscle damage to the heart.
    • Obtain a history of the patient’s complaints, including a list of known allergens, especially allergies or sensitivities to latex.
    • Obtain a history of the patient’s cardiovascular, hematopoietic, hepatobiliary, and musculoskeletal systems; symptoms; and results of previously performed laboratory tests and diagnostic and surgical procedures.
    • Obtain a list of the patient’s current medications, including herbs, nutritional supplements, and nutraceuticals (see Effects of Natural Products on Laboratory Values).
    • Review the procedure with the patient. (Samples at time of admission, 2 to 4 hr, 6 to 8 hr, and 12 hr after admission are the minimal recommendations. Additional samples may be requested.) Inform the patient that specimen collection takes approximately 5 to 10 min. Address concerns about pain and explain that there may be some discomfort during the venipuncture.
    • Sensitivity to social and cultural issues,  as well as concern for modesty, is important in providing psychological support before, during, and after the procedure.
    • Note that there are no food, fluid, or medication restrictions unless by medical direction.


    • Potential complications: N/A
    • Avoid the use of equipment containing latex if the patient has a history of allergic reaction to latex.
    • Instruct the patient to cooperate fully and to follow directions. Direct the patient to breathe normally and to avoid unnecessary movement.
    • Observe standard precautions, and follow the general guidelines in Patient Preparation and Specimen Collection. Positively identify the patient, and label the appropriate specimen container with the corresponding patient demographics, initials of the person collecting the specimen, date, and time of collection. Perform a venipuncture.
    • Remove the needle and apply direct pressure with dry gauze to stop bleeding. Observe/assess venipuncture site for bleeding or hematoma formation and secure gauze with adhesive bandage.
    • Promptly transport the specimen to the laboratory for processing and analysis.


    • Inform the patient that a report of the results will be made available to the requesting health-care provider (HCP), who will discuss the results with the patient.
    • Nutritional Considerations: Increased LDH levels may be associated with coronary artery disease (CAD). Nutritional therapy is recommended for the patient identified to be at risk for developing CAD or for individuals who have specific risk factors and/or existing medical conditions (e.g., elevated LDL cholesterol levels, other lipid disorders, insulin-dependent diabetes, insulin resistance, or metabolic syndrome). Other changeable risk factors warranting patient education include strategies to encourage patients, especially those who are overweight and with high blood pressure, to safely decrease sodium intake, achieve a normal weight, ensure regular participation in moderate aerobic physical activity three to four times per week, eliminate tobacco use, and adhere to a heart-healthy diet. If triglycerides also are elevated, the patient should be advised to eliminate or reduce alcohol. The 2013 Guideline on Lifestyle Management to Reduce Cardiovascular Risk published by the American College of Cardiology (ACC) and the American Heart Association (AHA) in conjunction with the National Heart, Lung, and Blood Institute (NHLBI) recommends a “Mediterranean”-style diet rather than a low-fat diet. The new guideline emphasizes inclusion of vegetables, whole grains, fruits, low-fat dairy, nuts, legumes, and nontropical vegetable oils (e.g., olive, canola, peanut, sunflower, flaxseed) along with fish and lean poultry. A similar dietary pattern known as the Dietary Approaches to Stop Hypertension (DASH) diet makes additional recommendations for the reduction of dietary sodium. Both dietary styles emphasize a reduction in consumption of red meats, which are high in saturated fats and cholesterol, and other foods containing sugar, saturated fats, trans fats, and sodium.
    • Social and Cultural Considerations: Numerous studies point to the prevalence of excess body weight in American children and adolescents. Experts estimate that obesity is present in 25% of the population ages 6 to 11 yr. The medical, social, and emotional consequences of excess body weight are significant. Special attention should be given to instructing the child and caregiver regarding health risks and weight-control education.
    • Recognize anxiety related to test results, and be supportive of fear of shortened life expectancy. Discuss the implications of abnormal test results on the patient’s lifestyle. Provide teaching and information regarding the clinical implications of the test results, as appropriate. Educate the patient regarding access to counseling services. Provide contact information, if desired, for the American Heart Association (, or the NHLBI (
    • Reinforce information given by the patient’s HCP regarding further testing, treatment, or referral to another HCP. Answer any questions or address any concerns voiced by the patient or family.
    • Depending on the results of this procedure, additional testing may be performed to evaluate or monitor progression of the disease process and determine the need for a change in therapy. Evaluate test results in relation to the patient’s symptoms and other tests performed.

    Related Monographs

    • Related tests include antiarrhythmic drugs, apolipoprotein A and B, AST, ANP, blood gases, BNP, calcium (blood and ionized), cholesterol (total, HDL, and LDL), CT cardiac scoring, CRP, CK and isoenzymes, echocardiogram, GGT, glucose, glycated hemoglobin, Holter monitor, homocysteine, ketones, lipoprotein electrophoresis, magnesium, MRI chest, MI scan, myocardial perfusion scan, myoglobin, pleural fluid analysis, PET heart, potassium, triglycerides, troponin, and US abdomen.
    • Refer to the Cardiovascular, Hematopoietic, Hepatobiliary, and Musculoskeletal systems tables at the end of the book for related tests by body system.
    Handbook of Laboratory and Diagnostic Tests, © 2013 Farlex and Partners