Blood Test May Predict Cognitive Decline in Healthy Older Adults

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 produced or processed by the liver. Common components include alanine aminotransferase (ALT), aspartate aminotransferase (AST), alkaline phosphatase (ALP), albumin, bilirubin, and total protein. Elevated or decreased levels of these markers can indicate different types of liver problems, from inflammation and infection to chronic disease or obstruction of bile ducts.

ALT and AST are enzymes found primarily in liver cells. When liver cells are damaged, these enzymes leak into the bloodstream, causing levels to rise. ALT is more specific to the liver, while AST can also be elevated due to heart or muscle problems. Alkaline phosphatase is an enzyme related to the bile ducts, and high levels may suggest bile duct blockage or bone disorders. Bilirubin is a waste product from the breakdown of red blood cells that the liver processes and eliminates. High bilirubin levels can cause jaundice, a yellowing of the skin and eyes, and may indicate liver dysfunction or bile duct problems.

Albumin and total protein measurements assess the liver's ability to produce essential proteins. Low albumin levels can indicate chronic liver disease, malnutrition, or kidney problems. Your doctor may order liver function tests if you have symptoms such as jaundice, abdominal pain, nausea, dark urine, or unexplained fatigue. These tests are also used to monitor existing liver conditions, assess the effects of medications that can impact the liver, or screen people at risk for liver disease due to factors like alcohol use, obesity, or family history.

Preparation for liver function tests typically requires fasting for eight to twelve hours before the blood draw, though your healthcare provider will give you specific instructions. The test involves a simple blood sample taken from a vein in your arm. Results are usually available within a few days. Abnormal results do not always mean you have a serious liver condition, as many factors can temporarily affect liver enzyme levels. Your doctor will interpret the results in the context of your symptoms, medical history, and possibly additional tests to determine the underlying cause and appropriate treatment if needed.