Liver Enzymes and Liver Function Tests and Results

Liver Enzyme Test Results Explained

Row of test tube with blood samples
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Liver Enzyme and Function Blood Test Results

Liver enzymes, or liver (hepatic) function tests, are common blood tests used to determine if the liver is functioning normally or if it has an injury or disease. These tests are done by drawing blood, typically in a doctor's office if liver disease is a known problem that requires monitoring, or in the hospital.  These blood tests can be part of a routine annual physical but are not always included.

These tests are drawn from a vein and sent to a lab for processing.  The liver enzyme test results are typically used together, not individually, to diagnose a liver problem. For example, one number being mildly elevated will not typically trigger a major examination of the liver.  If multiple tests indicate a problem, a liver biopsy may be necessary to confirm the test results, or a CT or MRI scan may be done.

Routine Liver Blood Tests

For some patients, these lab tests are part of routine monitoring if they are taking a medication known to cause liver problems.  This is because many medications--prescription, over the counter and supplements--are known to cause liver damage, or can cause problems with liver function.  

Drinking alcohol is also known to cause liver damage, if the amount of alcohol is excessive and the drinking occurs over an extended period of time.  For this reason, individuals who drink frequently may have their liver function checked to make sure no harm has been done.

 

For others, the liver may be known to have some problems that require routine monitoring to make sure that the condition isn't worsening.  For example, someone who is known to have a "fatty liver" or cirrhosis could potentially have labs drawn every six months and might even have a CT scan or ultrasound performed at the same time.

 

AST (Aspartate Phosphatase) Lab Results

This test is typically used to detect a liver injury or an active or chronic liver problem. The heart can also release AST, so it is important to look at the entire set of liver tests, rather than just this one test.

AST levels can be dramatically affected by shock, low blood pressure or any other condition that deprives the liver of blood and oxygen.

Normal Level:

Male: 8-46 units/liter

Female: 7-34 units/liter

ALT (Alanine Aminotransferase) Lab Results

This test is used to detect liver injuries and long-term liver disease. Highly elevated levels may indicate active hepatitis from any cause, including virus, alcohol, drug or toxin. Some prescription and over-the-counter medications can cause an increase in ALT levels.

ALT levels can be dramatically affected by shock, low blood pressure or any other condition that deprives the liver of blood and oxygen. For this reason, we can expect the sickest patients to have elevations in ALT, especially those who are being cared for in an intensive care area.

Normal level: 5-40 units per liter of blood serum

ALP (Alk Phos, Alkaline Phosphatase) Lab Results

ALP is a substance found in the bile ducts of the liver. Damage or obstruction of the bile ducts may result in elevated levels of ALP.

 That means an elevation in "alk phos" does't necessarily mean that the liver itself is having the problem, but the ducts that leave the liver may be the issue.

Normal Level: 13-39 units/liter

Total Bilirubin (T. Bili) Lab Results

This lab test measure the total amount of bilirubin in the blood, including direct and indirect bilirubin. Bilirubin is produced during the normal process of blood cells dying and the liver excretes bilirubin through bile. Too much bilirubin in the blood results in the patient looking yellow, or jaundiced. This test may detect elevated levels of bilirubin before jaundice is present.

Normal Level: 1mg per 100 ml

Indirect Bilirubin (I. Bili) Lab Results

Indirect bilirubin does not dissolve in water. In order to dissolve in water, and be eliminated from the body, it must go to the liver where it is made into direct (water soluble) bilirubin.

Indirect Bilirubin = Total Bilirubin – Direct Bilirubin

Direct Bilirubin (D. Bili) Lab Results

Direct bilirubin has been converted into a water soluble form of bilirubin by the liver. The proportion of indirect bili to direct bili may change if the liver has difficulty converting indirect into direct.

Normal Level: .4 mg per 100 ml

Albumin Lab Results

Albumin is a protein made by the liver that is very common in blood plasma, which can be measured in the blood. If the liver has chronic or acute damage, the level of albumin in the blood will typically be low. A low level of albumin can also be caused by poor nutrition, and is often seen in patients who are not eating well on a regular basis.  It can also be seen in patients who are chronically ill.

Normal Level: 3.5-5 grams/100 ml

Common Tests Before and After Surgery

Sources:

Liver Function Test. LabTestsOnline.org. The American Association of Clinical Chemistry http://www.labtestsonline.org/understanding/analytes/liver_panel/glance.html

 

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