The Liver Function Test (LFT) is a common blood panel used to assess liver health. It primarily screens for damage, monitors known liver disease progression, or assesses treatment effectiveness. The liver, located in the upper right side of the abdomen, performs hundreds of functions fundamental to health, including detoxifying blood, synthesizing proteins like albumin, and regulating metabolism. By measuring specific enzymes and proteins, the LFT signals when liver cells are injured or when the organ’s synthetic and excretory duties are compromised.
Accessing the Liver Function Test
Individuals typically obtain an LFT through a physician referral or a direct-to-consumer (DTC) lab order. The traditional route involves consulting a healthcare provider who determines if a medical indication warrants the test, such as monitoring medication side effects or investigating liver issues. If ordered by a physician, the LFT is generally covered by health insurance, though the patient may be responsible for a copay or deductible.
For those who prefer proactive screening or bypassing a doctor’s visit, direct-to-consumer testing is an available alternative. This method allows a person to purchase a liver panel online from a commercial lab without a physician’s approval. The out-of-pocket cost for a DTC liver panel can range from approximately $29 to over $100, depending on the number of markers included.
Once purchased, the individual visits a local patient service center for a blood draw, with results typically available through a secure online portal within a few days. Regardless of the ordering method, it is often recommended to fast (avoiding food and caloric beverages) for 10 to 12 hours before the blood draw to ensure accurate measurement. Avoiding strenuous physical activity in the 48 hours preceding the test is advisable, as intense exercise can temporarily elevate certain liver enzyme levels.
Understanding the Core Components of an LFT
A standard LFT panel measures several substances, each offering a unique perspective on the liver’s condition. The most common markers are enzymes suggesting cell integrity, such as Alanine Aminotransferase (ALT) and Aspartate Aminotransferase (AST). These enzymes normally reside within liver cells, assisting in the conversion of proteins into energy. When liver cells are damaged, they leak ALT and AST into the bloodstream, making elevated levels an indicator of hepatocellular injury.
Other components focus on the liver’s excretory function, notably Bilirubin and Alkaline Phosphatase (ALP). Bilirubin is a yellowish waste product created during the breakdown of old red blood cells. The liver processes and eliminates bilirubin in bile; accumulation in the blood may signal a problem with bile flow or processing. ALP is an enzyme found in the liver, bile ducts, and bone, and its presence helps assess the bile drainage system.
The panel also includes tests that measure the liver’s synthetic capacity, primarily Albumin and Total Protein. Albumin is the most abundant protein in the blood, and the liver is almost solely responsible for its production. Total Protein measures both albumin and other proteins. Low levels of these markers can indicate that the liver is not synthesizing proteins effectively, providing a comprehensive view of liver function.
Interpreting Elevated and Low Results
Interpreting an LFT requires understanding the context of the levels, as a single abnormal result is rarely diagnostic on its own. Elevated levels of the transaminase enzymes, ALT and AST, are the most common sign of liver cell damage, a pattern known as hepatocellular injury. Mild elevations (less than twice the upper limit of normal) can be transient. These may be caused by recent alcohol consumption, certain medications, or muscle injury from intense exercise.
Significantly higher elevations (sometimes greater than 1,000 International Units per liter, or IU/L) point toward an acute event, such as viral hepatitis, drug-induced liver injury, or lack of blood flow to the liver. The ratio of AST to ALT can provide a specific clue; for instance, an AST level twice as high as the ALT level often suggests liver damage related to chronic alcohol use.
When Bilirubin and ALP levels are elevated, especially in combination, it suggests a cholestatic pattern—an issue with the flow of bile. This pattern can be seen in conditions like gallstone obstruction or certain types of liver disease that affect the bile ducts. ALP can also be elevated due to conditions outside the liver, such as rapid bone growth or bone diseases.
Conversely, low levels of Albumin and Total Protein suggest a compromise in the liver’s ability to manufacture these components. Because the liver has significant reserve capacity, a drop in these synthetic markers is often a late-stage indicator, suggesting chronic liver disease like cirrhosis or severe malnutrition. Any result outside the laboratory’s reference range warrants immediate discussion with a healthcare provider. LFT results are merely data points; a full medical history, physical examination, and additional testing are required to determine the underlying cause and correct course of action.