ALT in a blood test stands for alanine transaminase, an enzyme primarily found in the liver. The ALT blood test measures the level of this enzyme in your blood to help diagnose liver damage or disease

. Normally, ALT levels in the blood are low because the enzyme is mostly inside liver cells. When liver cells are damaged due to injury, disease, or toxins, they release ALT into the bloodstream, causing elevated ALT levels

. The ALT test is often used alongside other liver function tests to assess liver health. High ALT levels may indicate conditions such as hepatitis, fatty liver disease, liver cirrhosis, liver tumors, or damage from drugs or alcohol

. Typical reasons for ordering an ALT test include symptoms of liver disease (like jaundice, nausea, or abdominal pain), risk factors such as heavy alcohol use or viral hepatitis exposure, or routine health screening

. Normal ALT levels usually range approximately from 7 to 56 units per liter (U/L), though this can vary slightly by lab. Elevated ALT levels can vary in significance:

• Mild elevation may indicate early or mild liver damage.
• Levels 4 times above normal may suggest chronic hepatitis or cirrhosis.
• Levels 10 times above normal often indicate acute hepatitis.
• Extremely high levels (100 times normal) can occur with severe liver injury from toxins or drugs

Low ALT levels generally are not clinically significant unless accompanied by other symptoms

. In summary, ALT is a liver enzyme measured in blood tests to detect liver injury or disease, with higher levels signaling potential liver damage