Woman Undergoes Therapeutic Phlebotomy to Remove 14 Pints of Blood

Liver function tests are a group of blood tests that help evaluate how well your liver is working and detect potential liver damage or disease. These tests measure various enzymes, proteins, and substances that the liver produces or processes. When your liver is injured or diseased, it releases certain enzymes and proteins into your bloodstream, or it may produce abnormal amounts of substances it normally regulates.

The most common liver function tests include measurements of alanine aminotransferase (ALT) and aspartate aminotransferase (AST), which are enzymes that leak into the blood when liver cells are damaged. Alkaline phosphatase (ALP) and gamma-glutamyl transferase (GGT) are also measured to assess bile duct function and liver health. Additionally, these tests typically measure bilirubin, a waste product from the breakdown of red blood cells that the liver processes, and albumin, a protein made by the liver that helps maintain fluid balance in the body. Prothrombin time or INR may also be included to assess the liver's ability to produce blood clotting factors.

Your doctor may order liver function tests for several reasons. They are commonly used to screen for liver infections like hepatitis, monitor the progression of liver disease, check for side effects of medications that can affect the liver, or investigate symptoms such as jaundice, abdominal pain, nausea, or unexplained fatigue. These tests can also help monitor treatment effectiveness for existing liver conditions and assess liver health before starting certain medications.

Abnormal liver function test results do not always mean you have a serious liver problem. Results outside the normal range can be caused by temporary conditions, certain medications, alcohol consumption, obesity, or other health conditions unrelated to the liver. If your results are abnormal, your healthcare provider will consider your medical history, symptoms, and other test results to determine whether additional testing or treatment is needed. Repeat testing may be recommended to confirm results or monitor changes over time.

Preparing for liver function tests typically requires fasting for eight to twelve hours before the blood draw, though requirements may vary depending on which specific tests are ordered. You should inform your healthcare provider about all medications, supplements, and herbal products you are taking, as some can affect test results. The blood sample is usually taken from a vein in your arm, and results are typically available within a few days.