LFT

Liver function tests, also known as liver chemistries, help determine the health of your liver by measuring the levels of proteins, liver enzymes, and bilirubin in your blood.

A liver function test is often recommended in the following situations:

• to check for damage from liver infections, such as hepatitis B and hepatitis C
• to monitor the side effects of certain medications known to affect the liver
• if you already have a liver disease, to monitor the disease and how well a particular treatment is working
• if you’re experiencing the symptoms of a liver disorder
• if you have certain medical conditions such as high triglycerides, diabetes, high blood pressure, or anemia
• if you drink alcohol heavily
• if you have gallbladder disease

Many tests can be performed on the liver. Certain tests can reflect different aspects of liver function.

Commonly used tests to check liver abnormalities are tests checking:

• alanine transaminase (ALT)
• aspartate aminotransferase (AST)
• alkaline phosphatase (ALP)
• albumin
• bilirubin

The ALT and AST tests measure enzymes that your liver releases in response to damage or disease. The albumin test measures how well the liver creates albumin, while the bilirubin test measures how well it disposes of bilirubin. ALP can be used to evaluate the bile duct system of the liver.

Having abnormal results on any of these liver tests typically requires follow up to determine the cause of the abnormalities. Even mildly elevated results can be associated with liver disease. However, these enzymes can also be found in other places besides the liver.

Talk to your doctor about the results of your liver function test and what they may mean for you.

Alanine transaminase (ALT) test

Alanine transaminase (ALT) is used by your body to metabolize protein. If the liver is damaged or not functioning properly, ALT can be released into the blood. This causes ALT levels to increase.

A higher than normal result on this test can be a sign of liver damage.

According to the American College of Gastroenterology, an ALT above 25 IU/L (international units per liter) in females and 33 IU/L in males typically requires further testing and evaluation.

Aspartate aminotransferase (AST) test

Aspartate aminotransferase (AST) is an enzyme found in several parts of your body, including the heart, liver, and muscles. Since AST levels aren’t as specific for liver damage as ALT, it’s usually measured together with ALT to check for liver problems.

When the liver is damaged, AST can be released into the bloodstream. A high result on an AST test might indicate a problem with the liver or muscles.

The normal range for AST is typically up to 40 IU/L in adults and may be higher in infants and young children.

Alkaline phosphatase (ALP) test

Alkaline phosphatase (ALP) is an enzyme found in your bones, bile ducts, and liver. An ALP test is typically ordered in combination with several other tests.

High levels of ALP may indicate liver inflammation, blockage of the bile ducts, or a bone disease.

Children and adolescents may have elevated levels of ALP because their bones are growing. Pregnancy can also raise ALP levels. The normal range for ALP is typically up to 120 U/L in adults.

Albumin test

Albumin is the main protein made by your liver. It performs many important bodily functions. For example, albumin:

• stops fluid from leaking out of your blood vessels
• nourishes your tissues
• transports hormones, vitamins, and other substances throughout your body

An albumin test measures how well your liver is making this particular protein. A low result on this test can indicate that your liver isn’t functioning properly.

The normal range for albumin is 3.5–5.0 grams per deciliter (g/dL). However, low albumin can also be a result of poor nutrition, kidney disease, infection, and inflammation.

Bilirubin test

Bilirubin is a waste product from the breakdown of red blood cells. It’s ordinarily processed by the liver. It passes through the liver before being excreted through your stool.

A damaged liver can’t properly process bilirubin. This leads to an abnormally high level of bilirubin in the blood. A high result on the bilirubin test may indicate that the liver isn’t functioning properly.

The normal range for total bilirubin is typically 0.1–1.2 milligrams per deciliter (mg/dL). There are certain inherited diseases that raise bilirubin levels, but the liver function is normal.

What are the symptoms of a liver disorder?

Symptoms of a liver disorder include:

• weakness
• fatigue or loss of energy
• weight loss
• jaundice (yellow skin and eyes)
• fluid collection in the abdomen, known as ascites
• discolored bodily discharge (dark urine or light stools)
• nausea
• vomiting
• diarrhea
• abdominal pain
• abnormal bruising or bleeding

Your doctor may order a liver function test if you’re experiencing symptoms of a liver disorder. The different liver function tests can also monitor the progression or treatment of a disease and test for the side effects of certain medications.