At a Glance
Why Get Tested?
When to Get Tested?
Test Preparation Needed?
The Test Sample
What is being tested?
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 (slightly different molecular versions of the LDH enzyme). A total LDH level will reflect the tissue damage done but it is not specific. 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, muscle
How is the sample collected for testing?
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?
Ask a Laboratory Scientist
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.