Liver Function Tests

Liver function tests (LFTs) are a group of blood tests that check enzymes, proteins, and other substances produced or processed by the liver, giving a general picture of liver health and function.

What's Typically Measured

• ALT and AST — liver enzymes that rise when liver cells are damaged or inflamed
• Alkaline phosphatase (ALP) — can rise with certain liver or bile duct conditions
• Bilirubin — a breakdown product the liver processes; elevated levels can cause jaundice
• Albumin and total protein — proteins made by the liver, which can drop if liver function is significantly impaired

When These Tests Are Ordered

Doctors commonly order liver function tests as part of routine health screening, to investigate symptoms like fatigue or abdominal discomfort, to monitor certain medications known to affect the liver, or to evaluate risk factors for conditions like fatty liver disease.

What Abnormal Results Can Mean

Mildly elevated liver enzymes are common and don't always indicate serious disease — they can reflect anything from recent alcohol use to certain medications to fatty liver disease. Significantly abnormal results, or a pattern that persists over repeat testing, usually prompts further evaluation to identify the specific cause.

Doctors often look at which results are most elevated to narrow down the cause: a hepatocellular pattern (ALT and AST rising the most) suggests liver cell injury, while a cholestatic pattern (ALP and bilirubin rising the most) suggests a problem with bile flow — this pattern helps guide which further tests are needed.