What is a liver function test?
A liver function test (LFT) or liver chemistries, is a blood test that measures enzymes and proteins in the blood. Enzyme tests in liver test show the extent of damage to a liver, while proteins show how well a liver is performing. An LFT is a diagnostic tool used to detect whether a person’s liver is damaged, and can also be a screening tool for measuring the severity and type of liver disease.
hy would I need this test?
You may need this test for the following:
- Screen for liver infections, such as hepatitis
- Monitor the progression of liver disease, such as viral hepatitis or alcoholic hepatitis and determine how well a treatment is working.
- Measure the severity of liver disease, particularly scarring of the liver (cirrhosis)
- Monitor possible side effects of medications
The test will allow our doctors to figure out a diagnosis and see how well to treat and how well you are responding to treatment after the diagnosis.
How do I prepare for an LFT test?
You may need to avoid taking certain medicines before the test because they might affect the test result. Make sure you inform our doctors about any medicines, herbs, or supplements that you are taking. You can ask our doctors before stopping any of your regular medicines. Talk to our doctors if you have any questions about the test. It can be done at any time of the day.
What are the most common liver function tests?
Some common liver function tests include:
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.
An ALT above 35 IU/L (international units per liter) in females and 40 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 306 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 is not 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 is not 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.
How is an LFT performed?
This test involves a simple blood draw. It should take only a minute or two.
- First, the skin directly over your vein will be cleaned by the blood test technician to prevent any substances on your skin to avoid contamination of the test.
- They will wrap your arm with some sort of pressure device to make the veins more visible. Then, a needle will be inserted to collect your blood.
- After collecting your blood, the needle is removed and the puncture site covered to stop any bleeding.
The LFT for children
There is very little difference between children’s veins and adult veins. Therefore the procedure is very similar. Children can be quite scared of needles, though, so it is important that the parent and medical practitioner both encourage the child to remain calm and relaxed. You may wish to explain to the child that it only stings for a very short time, and offer them a treat afterwards.
Blood sample analysis
The analysis of the collected blood is carried out by our laboratory scientist using an analyzer in a pathology laboratory. The laboratory will send the results to our doctors.
What do the results of my LFT test mean?
Normal blood test results for typical liver function tests include:
- 5 to 40 units per liter (U/L)
- 5 to 40 U/L
- 80 to 306 U/L
- 3.5 to 5.0 grams per deciliter (g/dL)
- Total protein. 6.0 to 8.5 g/dL
- 0.1 to 1.2 milligrams per deciliter (mg/dL)
- 5 to 50 U/L
These results are typical for adult. Normal results vary from laboratory to laboratory and might be slightly different for women and children.
Our doctors will use these results to help diagnose your condition or determine treatment you might need. If you already have liver disease, liver function tests can help determine how your disease is progressing and if you're responding to treatment.
Are there any risks to the test?
People who take the test may feel a slight sting when the needle pricks the arm. Some people may bleed slightly where the needle pierces the skin, and others may feel temporarily faint or dizzy.
After the test, people may get a small bruise at the puncture site or experience mild soreness in the arm, which can last for a few days. In more sensitive people, this bruising may turn into a hematoma.
