Liver Function Test

Your doctor may order an LFT if you have:

• Yellowing of the skin or eyes (jaundice)
• Abdominal pain, swelling, or tenderness, particularly in the upper right area
• Unexplained fatigue, nausea, or loss of appetite
• Dark urine or pale, clay-colored stools
• A history of heavy alcohol use or known hepatitis exposure
• Before starting medications known to affect the liver, and periodically while taking them

LFTs are used to detect and monitor:

• Viral hepatitis (A, B, and C)
• Alcoholic liver disease
• Non-alcoholic fatty liver disease (NAFLD)
• Liver cirrhosis
• Bile duct obstruction or gallstones
• Drug-induced liver injury

1. Fasting for 8–10 hours is usually recommended, especially if the panel is being combined with a lipid or glucose test.
2. Avoid alcohol for at least 24 hours before the test, as it can temporarily elevate liver enzymes.
3. Tell your doctor about all medications and supplements you take, since several common drugs can affect liver enzyme levels.
4. Avoid strenuous exercise the day before testing, as intense physical activity can also mildly raise certain liver enzymes.

Reference ranges vary somewhat by lab and testing method.

Mildly elevated ALT and AST are relatively common and often reflect fatty liver or recent alcohol use, while sharply elevated levels (several times the upper limit) usually indicate acute liver injury such as viral hepatitis or drug toxicity and warrant prompt medical attention.