Lactate dehydrogenase (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. LD is released from the cells into the bloodstream when cells are damaged or destroyed. Because of this, the LD test can be used as a general marker of injury to cells.

Although there is some overlap, each of the five LD isoenzymes tends to be concentrated in specific body tissues. In general, the isoenzyme locations are as follows:

• LD₁: Heart, red blood cells, kidney

• LD₂: Heart, red blood cells, kidney (lesser amounts than LD₁)

• LD₃: Lungs and other tissues

• LD₄: White blood cells, lymph nodes, muscle, liver (lesser amounts than LD₅)

• LD₅: Liver, skeletal muscle

Changes of LD isoenzymes periodically measured following onset of chest pain, studying the relationships of the anodic fractions, provide important information for the differential diagnosis of acute infarct of myocardium. The differential diagnosis of certain other diseases is enhanced as well with the use of LD isoenzymes.

Useful in the differential diagnosis of acute myocardial infarction, megaloblastic anemia (folate deficiency, pernicious anemia), hemolytic anemia, and very occasionally renal infarct. These entities are characterized by LD₁ increases, often with LD₁:LD₂ inversion.

The isomorphic pattern (total LD significantly high with no increase in percentage, of any fraction) is seen with neoplasia, cardiorespiratory diseases, hypothyroidism, infectious mononucleosis, and other inflammatory states, uremia, and necrosis.

LD₅ increases are seen with striated muscle lesions (eg, trauma) and with liver diseases (eg, hepatic congestion, congestive heart failure, hepatitis, cirrhosis, alcoholism). LD₅ increase is probably more significant when the LD₅:LD₄ ratio is increased.

After placing an order, you will receive a doctor approved lab order by email usually within 20-30 minutes. The emailed Lab Requisition will allow you to go to a local patient collection site to get tested. You will not have to pay any additional lab, collection or doctor's fees.  Most test will normally report within 48-72 hours by secure email. List of collections site can be found using our Lab Locator Tool. If you have any questions please call our offices at 1-844-455-6355 or chat online with a member of our Care Team.