Hepatic Aminotransferase Activity (Serum) – Alanine Aminotransferase (ALT) Activity

What ALT Measures

ALT is an enzyme produced mainly in your liver, but also in smaller amounts in other organs like the heart and kidneys. When liver cells are injured (due to infection, toxins, or disease), ALT leaks into the bloodstream, increasing its level. This test specifically measures ALT’s ability to transfer amino acids, reflecting liver function and integrity.

Why It’s Done

Your healthcare provider may order this test to investigate symptoms like jaundice (yellowing skin/eyes), fatigue, abdominal pain, or unexplained nausea. It’s also used to monitor liver disease progression, response to treatment, or detect early liver damage before symptoms appear.

Common Causes of Elevated ALT

High ALT levels can result from liver conditions such as hepatitis (viral, alcoholic, or autoimmune), fatty liver disease, or certain medications/toxins. Non-liver causes may include heart attacks, muscle disorders, or certain infections.

What to Expect During the Test

A simple blood draw is needed. You’ll lie down comfortably while a healthcare provider inserts a needle into your arm to collect a small blood sample. The process takes about 5 minutes, and you may experience mild discomfort or bruising afterward.