At a Glance
Why Get Tested?
To help identify the cause and location of tissue damage in the body and to monitor its progress; LDH is elevated in a wide variety of conditions, reflecting its widespread tissue distribution; historically, it has been used to help diagnose and monitor a heart attack, but troponin has largely replaced LDH in this role.
When to Get Tested?
Along with other tests, when your doctor suspects that you have an acute or chronic condition that is causing tissue or cellular destruction and he wants to identify the source of the damage and monitor the problem
A blood sample drawn from a vein in your arm
Test Preparation Needed?
The Test Sample
What is being tested?
Lactate dehydrogenase (LDH or LD) is an enzyme that is found in almost all of the body's cells, but only a small amount of it is usually detectable in the blood. LDH is released from the cells into the bloodstream when cells are damaged or destroyed. Because of this, the LDH test can be used as a general marker of injury to cells.
Elevations of LDH may be measured either as a total LDH or as LDH isoenzymes. A total LDH level is an overall measurement of five different LDH isoenzymes. Isoenzymes are slightly different molecular versions of the LDH enzyme. A total LDH level will reflect the presence of tissue damage but, by itself, it cannot be used to identify the underlying cause or its location.
Although there is some overlap, each of the five LDH isoenzymes tends to be concentrated in specific body tissues. Because of this, measurements of the individual LDH isoenzyme levels can be used, along with other tests, to help determine the disease or condition causing cellular damage and to help identify the organs and tissues involved. In general, the isoenzyme locations tend to be:
- LDH-1: heart, red cells, kidney, germ cells
- LDH-2: heart, red blood cells, kidney (lesser amounts than LDH-1)
- LDH-3: lungs and other tissues
- LDH-4: white blood cells, lymph nodes, muscle, liver (lesser amounts than LDH-5)
- LDH-5: liver, skeletal muscle
While all of the isoenzymes are represented in the total LDH, LDH-2 usually makes up the greatest percentage.
How is the sample collected for testing?
A blood sample is obtained by inserting a needle into a vein in the arm.
NOTE: If undergoing medical tests makes you or someone you care for anxious, embarrassed, or even difficult to manage, you might consider reading one or more of the following articles: Coping with Test Pain, Discomfort, and Anxiety, Tips on Blood Testing, Tips to Help Children through Their Medical Tests, and Tips to Help the Elderly through Their Medical Tests.
Another article, Follow That Sample, provides a glimpse at the collection and processing of a blood sample and throat culture.
Is any test preparation needed to ensure the quality of the sample?
No test preparation is needed.
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NOTE: This article is based on research that utilizes the sources cited here as well as the collective experience of the Lab Tests Online Editorial Review Board. This article is periodically reviewed by the Editorial Board and may be updated as a result of the review. Any new sources cited will be added to the list and distinguished from the original sources used.
Sources Used in Current Review
Vorvick, L. and Zieve, D. (Updated 2009 March 14). LDH isoenzymes. MedlinePlus Medical Encyclopedia [On-line information] Available online at http://www.nlm.nih.gov/medlineplus/ency/article/003499.htm. Accessed October 2010.
Vorvick, L. and Zieve, D. (Updated 2010 March 21). Lactate Dehydrogenase Test. MedlinePlus Medical Encyclopedia [On-line information] Available online at http://www.nlm.nih.gov/medlineplus/ency/article/003471.htm. Accessed October 2010.
Shaffer, E. (Revised 2009 June). Testing for Hepatic and Biliary Disorders, Laboratory Tests. Merck Manual for Healthcare Professionals [On-line information] Available online at http://www.merck.com/mmpe/sec03/ch023/ch023b.html through http://www.merck.com. Accessed October 2010.
(© 1995-2010). Unit Code 8344: Lactate Dehydrogenase (LD), Serum. Mayo Clinic, Mayo Medical Laboratories [On-line information] Available online at http://www.mayomedicallaboratories.com/test-catalog/Overview/8344 through http://www.mayomedicallaboratories.com. Accessed October 2010.
Blood Test: Lactate Dehydrogenase (LDH). KidsHealth from Nemours Foundation [On-line information] Available online at http://kidshealth.org/parent/system/medical/test_ldh.html through http://kidshealth.org. Accessed October 2010.
Pagana, K. D. & Pagana, T. J. (© 2007). Mosby's Diagnostic and Laboratory Test Reference 8th Edition: Mosby, Inc., Saint Louis, MO. Pp 581-583.
Wu, A. (© 2006). Tietz Clinical Guide to Laboratory Tests, 4th Edition: Saunders Elsevier, St. Louis, MO. Pp 648-651.
Tietz Textbook of Clinical Chemistry and Molecular Diagnostics. Burtis CA, Ashwood ER, Bruns DE, eds. St. Louis: Elsevier Saunders; 2006, Pp 601-602.
Sources Used in Previous Reviews
Thomas, Clayton L., Editor (1997). Taber's Cyclopedic Medical Dictionary. F.A. Davis Company, Philadelphia, PA [18th Edition].
Pagana, Kathleen D. & Pagana, Timothy J. (2001). Mosby's Diagnostic and Laboratory Test Reference 5th Edition: Mosby, Inc., Saint Louis, MO.
Lactate Dehydrogenase. ARUP's Guide to Clinical laboratory Testing [On-line information]. Available online at http://www.aruplab.com/guides/clt/tests/clt_a32b.htm#1140532 through http://www.aruplab.com.
(2002 October 25, Updated). LDH isoenzymes. MEDLINEplus Health Information [On-line information]. Available online at http://www.nlm.nih.gov/medlineplus/ency/article/003499.htm.
(2001 November 20, Updated). LDH. MEDLINEplus Health Information [On-line information]. Available online at http://www.nlm.nih.gov/medlineplus/ency/article/003471.htm.
Spengler, R. (2002 May 14, Updated). What is lactate dehydrogenase (LDH)? St. Joseph's Hospital, Health Library, Medical Tests [On-line information]. Available online at http://www.sjo.org/library/healthguide/MedicalTests/topic.asp?hwid=tv6793abc through http://www.sjo.org.
Martin, G. (1998 March 9). The Obsolescence of Lactate Dehydrogenase Testing. American Medical Association, Archives of internal Medicine, Editor's Correspondence, Vol. 158 No. 5 [On-line information]. Available online at http://archinte.ama-assn.org/issues/v158n5/ffull/ilt0309-4.html through http://archinte.ama-assn.org.
Spengler, R. (2002 May 14, Updated). Cardiac Enzyme Studies. WebMD [On-line information]. Available online at http://my.webmd.com/printing/article/1675.55521 through http://my.webmd.com.
Lactate dehydrogenase isoenzymes test. Hendrick Health System, AccessMed Health Information Library [On-line information]. Available online at http://www.hendrickhealth.org/healthy/00054240.html through http://www.hendrickhealth.org.
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Pagana, Kathleen D. & Pagana, Timothy J. (© 2007). Mosby's Diagnostic and Laboratory Test Reference 8th Edition: Mosby, Inc., Saint Louis, MO. Pp 581-582.
Clarke, W. and Dufour, D. R., Editors (2006). Contemporary Practice in Clinical Chemistry, AACC Press, Washington, DC. Chapter 23 Laboratory Diagnosis of Liver Disease, Pp 269 - 279.
Wu, A. (2006). Tietz Clinical Guide to Laboratory Tests, Fourth Edition. Saunders Elsevier, St. Louis, Missouri. Pg 652.
(2007 March 13, Updated). LDH. MedlinePlus Medical Encyclopedia [On-line information]. Available online at http://www.nlm.nih.gov/medlineplus/ency/article/003471.htm. Accessed on 7/9/07.