Liver Blood Tests (cont.)
Siamak T. Nabili, MD, MPH
Dr. Nabili received his undergraduate degree from the University of California, San Diego (UCSD), majoring in chemistry and biochemistry. He then completed his graduate degree at the University of California, Los Angeles (UCLA). His graduate training included a specialized fellowship in public health where his research focused on environmental health and health-care delivery and management.
William C. Shiel Jr., MD, FACP, FACR
Dr. Shiel received a Bachelor of Science degree with honors from the University of Notre Dame. There he was involved in research in radiation biology and received the Huisking Scholarship. After graduating from St. Louis University School of Medicine, he completed his Internal Medicine residency and Rheumatology fellowship at the University of California, Irvine. He is board-certified in Internal Medicine and Rheumatology.
In this Article
- What are the basic functions of the liver?
- What are common liver blood tests?
- What are the aminotransferases?
- Normally, where are the aminotransferases?
- What are normal levels of AST and ALT?
- What do elevated liver tests (AST and ALT) mean?
- Does AST and ALT measurements indicate liver function?
- Which blood tests are done to detect liver function?
- What are some common reasons for abnormal liver tests?
- What medications can cause abnormal aminotransferase levels?
- What conditions can cause very high aminotransferase levels?
- What are some of the less common causes of elevated liver blood tests?
- How are healthy people evaluated for mild to moderate rises in aminotransferase levels?
- How about monitoring liver blood tests?
- What about the other liver enzymes?
- Hepatitis Slideshow Pictures
- Take the Alcohol Quiz
- Alcohol Abuse Slideshow Pictures
Does AST and ALT measurements indicate for liver function?
It is important to clarify that ALT and AST levels do not reflect the function of the liver, even though they commonly are referred to as liver function tests or LFTs. They only are used to detect inflammation due to injury or damage to the liver from any source. Even in conditions when AST and ALT are very elevated, the liver may function properly.
What blood tests are done to detect liver function?
The blood tests that truly reflect the liver function are the following:
- Coagulation panel (prothrombin time or PT, and international
normalized ratio or INR): These tests measure blood's ability for normal
clotting and prevention of bleeding and
bruising. This is the function of
certain proteins called clotting factors that are produced in the normally
functioning liver.
- Albumin level (hypoalbuminemia): Albumin is a very common protein
found in the blood with a variety of functions. It also is produced only in
the liver, and if its levels are lower than normal it can be suggestive of
chronic liver disease. Of note, other conditions may also cause low albumin
levels.
- Bilirubin: This byproduct of the routine destruction of red blood
cells occurring in the liver is released as bile in the feces. Elevation of
the bilirubin can suggest liver dysfunction.
- Platelet count: Low platelet count (thrombocytopenia) has many causes, one of which can be advanced liver disease.
What are some common reasons for abnormal liver tests?
Abnormal liver tests may be detected in the blood in a variety of liver conditions.
- Mild to moderate elevations of the liver enzymes are common. They
are often unexpectedly encountered on routine blood screening tests in
otherwise healthy individuals. The AST and ALT levels in such cases are
usually between twice the upper limits of normal and several hundred
units/liter. One of the most common cause of mild to moderate elevations of
these liver tests is a condition referred to as fatty liver. In the United States,
the most frequent cause of fatty liver is alcohol abuse. Other causes of
fatty liver include diabetes mellitus and obesity.
- Chronic hepatitis B and hepatitis C is a cause of chronic mild to
moderate liver enzyme elevations.
- Chronic and acute alcohol use is also a common cause of abnormal liver
tests.
- Some medications can cause mild to moderate increase in the liver enzymes.
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