Health Library

What Is a Blood Test?

By taking and testing a small sample of a person’s blood, doctors can check for many kinds of diseases and conditions. Blood tests help doctors check how the body’s organs are working and see if medical treatments are helpful.

To help your child get ready for a blood test, find out if they need to fast (not eat or drink) or should stop taking medicines before the test. Explain what to expect during the test. If your child is anxious about it, work together on ways to stay calm.

What Is Lactate Dehydrogenase?

Lactate dehydrogenase (LDH) is an enzyme that’s in almost all body tissues. It helps the body turns glucose (sugar) from food into usable energy for our cells.

LDH (also called lactic acid dehydrogenase) blood levels usually are low. But tissues damaged by injury or disease release more of the enzyme into the bloodstream. This can happen from liver disease, a heart attack, anemia, muscle trauma, bone fractures, cancers, or an infection such as meningitis, encephalitis, and HIV.

Why Are Lactate Dehydrogenase Tests Done?

This test measures the amount of LDH in the blood. Doctors may order an LDH test to screen for tissue damage. This damage may be acute (as from a traumatic injury) or chronic (from a long-term condition such as liver disease or some types of anemia). They also can use the test to monitor progressive conditions, such as muscular dystrophy.

What if I Have Questions?

If you have questions about the LDH test or what the test results mean, talk to your doctor.