ALT is a blood test that determines the level of the enzyme alanine transaminase (ALT) in the blood.
ALT is present in many different kinds of tissue in the body. However, it is highly concentrated in the liver. Therefore, when the liver is injured, ALT is released into the bloodstream. An ALT test may be ordered when the healthcare provider suspects liver disease or other damage to the liver.
A blood sample needs to be taken in order to measure the level of ALT. The blood is usually drawn from a vein in the forearm or the hand. First, the skin over the vein is cleaned with an antiseptic. Next, a strong rubber tube called a tourniquet is wrapped around the upper arm. This enlarges the veins in the lower arm by restricting blood flow through them. A very thin needle is gently inserted into a vein, and the tourniquet is removed. Blood flows from the vein through the needle and is collected in a syringe or vial. The sample is sent to the lab to be analyzed. After the needle is withdrawn, the puncture site is covered for a short time to prevent bleeding.
Generally, no preparation is needed for an ALT blood test.
Normally, ALT levels range from 6 to 59 units per liter (U/L). Elevated levels of ALT may indicate one of the following conditions:
Author:David T. Moran, MD
Editor:Keefe, Sandy, RN, MSN
Reviewer:Eileen McLaughlin, RN, BSN