What do the results of an ALT measurement test mean?

An alanine aminotransferase (ALT) test measures the amount of this enzyme in the blood. Results are usually available within 12 hours.

The normal values listed here—called a reference range—are just a guide. These ranges vary from lab to lab, and your lab may have a different range for what’s normal. Your lab report should contain the range your lab uses. Also, your doctor will evaluate your results based on your health and other factors. This means that a value that falls outside the normal values listed here may still be normal for you or your lab.

Alanine aminotransferase:

• Males: 10–40 units per liter (U/L) or 0.17–0.68 microkats per liter (mckat/L) 
• Females: 7–35 U/L or 0.12–0.60 mckat/L

High levels of ALT may be caused by:

• Liver damage from conditions such as hepatitis or cirrhosis.
• Lead poisoning.
• Exposure to carbon tetrachloride.
• Decay of a large tumor (necrosis).
• Many medicines, such as statins, antibiotics, chemotherapy, aspirin, narcotics, and barbiturates.
• Mononucleosis.
• Growth spurts, especially in young children. Rapid growth can cause mildly elevated levels of ALT.