The lactate dehydrogenase (LDH) isoenzyme test checks how much of the different types of LDH are in the blood.
How the Test is Performed
A blood sample is needed.
How to Prepare for the Test
The health care provider may tell you to temporarily stop taking certain medicines before the test.
Drugs that can increase LDH measurements include:
DO NOT stop taking any medicine before talking to your provider.
How the Test will Feel
When the needle is inserted to draw blood, some people feel slight pain. Others feel only a prick or stinging. Afterward, there may be some throbbing or a slight bruise. This soon goes away.
Why the Test is Performed
This test is usually done when your doctor thinks you might have high LDH levels. Measurement of LDH isoenzymes helps determine the location of any tissue damage.
LDH is found in many body tissues such as the heart, liver, kidney, skeletal muscle, brain, blood cells, and lungs.
LDH exists in five forms, which differ slightly in structure.
- LDH-1 is found primarily in heart muscle and red blood cells.
- LDH-2 is concentrated in white blood cells.
- LDH-3 is highest in the lung.
- LDH-4 is highest in the kidney, placenta, and pancreas.
- LDH-5 is highest in the liver and skeletal muscle.
All of these can be measured in the blood.
What Abnormal Results Mean
LDH levels that are higher than normal may suggest:
Veins and arteries vary in size from one person to another and from one side of the body to the other. Drawing blood from some people may be more difficult than from others.
Other risks associated with having blood drawn are slight but may include:
- Excessive bleeding
- Fainting or feeling lightheaded
- Hematoma (blood accumulating under the skin)
- Infection (a slight risk any time the skin is broken)
LD; Lactic (lactate) dehydrogenase isoenzymes
Pincus MR, Abraham NZ Jr, Carty RP. Clinical enzymology. In: McPherson RA, Pincus MR, eds. Henry's Clinical Diagnosis and Management by Laboratory Methods. 22nd ed. Philadelphia, PA: Elsevier Saunders; 2011:chap 20.
Selcen D. Muscle diseases. In: Goldman L, Schafer AI, eds. In: Goldman's Cecil Medicine. 25th ed. Philadelphia, PA: Elsevier Saunders; 2016:chap 421.
Update Date 1/31/2015
Updated by: Linda J. Vorvick, MD, Medical Director and Director of Didactic Curriculum, MEDEX Northwest Division of Physician Assistant Studies, Department of Family Medicine, UW Medicine, School of Medicine, University of Washington, Seattle, WA. Also reviewed by David Zieve, MD, MHA, Isla Ogilvie, PhD, and the A.D.A.M. Editorial team.