What Are Liver Function Tests?
Liver function tests help determine the health of your liver by measuring levels of proteins, enzymes, or bilirubin in your blood.
Many tests can be performed on the liver, but most of them do not measure the overall function of the liver. The most widely used tests to check liver function are the albumin test and the bilirubin test. These tests measure how well the liver creates albumin, a protein, and disposes of bilirubin, a waste product of the blood.
Albumin is the main protein made by the liver. It performs many important bodily functions. For instance, albumin:
- stops fluid from leaking out of blood vessels
- nourishes tissues
- transports hormones, vitamins, and other substances throughout the body.
An albumin test measures how well the liver is making this particular protein. A low result on this test indicates that the liver is not functioning properly.
Bilirubin, on the other hand, is a waste product ordinarily processed by the liver. This waste product is caused by the breakdown of red blood cells. It passes through the liver before being excreted through your stool.
If your liver is damaged, it cannot properly process bilirubin. This will lead to an abnormally high level of bilirubin in the blood. Thus, a high result on the bilirubin test indicates that the liver is not functioning properly.
Why a Liver Function Test Is Done
Liver tests are performed to determine if the liver is working correctly. The liver performs a number of vital bodily functions, such as:
- removing contaminants from the blood
- converting the nutrients from the food you eat
- storing minerals and vitamins
- regulating blood clotting
- producing proteins, enzymes, and bile
- making factors that fight infection
- removing bacteria from the blood
- processing substances that could harm the body
- maintaining hormone balances
Problems with the liver can make a person very sick and can lead to death.
Your doctor may order a liver function test if you are experiencing symptoms of a liver disorder or even if you’re planning to become pregnant.
Symptoms of a liver disorder include:
- fatigue or loss of energy
- weight loss
- jaundice (yellow skin and eyes)
- symptoms of nephritic syndrome (swelling around the eyes, belly, and legs)
- discolored bodily discharge (dark urine or light stools)
- abdominal pain
The different liver function tests can check for infection, monitor the progression or treatment of a disease, and test for the side effects of certain medications.
How to Prepare for a Liver Function Test
Your doctor will give you complete instructions on how to prepare for the blood sample portion of the test. This could include not taking certain medications or fasting for a period of time before the test.
You may want to wear a shirt with sleeves that can easily be rolled up so the nurse or technician can collect the blood sample. This can make the process that much easier.
How a Liver Function Test Is Performed
The blood draw may be performed in a hospital or at a specialized testing facility.
Your skin will be cleaned before the test to prevent any microorganisms on your skin from contaminating the test.
The nurse or technician will likely wrap a cuff or some sort of pressure device on your arm. This will help the veins become more visible. He or she will use a needle to draw several samples of blood from your arm.
After the draw, the nurse or technician will place some gauze and a bandage over the puncture site.
The blood sample will be sent to a laboratory for testing.
After a Liver Function Test
After the test, you can usually leave and go about your life as usual. However, if you feel faint or light-headed during the blood draw, you cannot leave right away. If you experienced these symptoms, you’ll have to rest before you leave the testing facility.
When the results are available from the laboratory, your doctor will review them. He or she may call you with the results or discuss them with you at a follow-up appointment.
Normal levels for the albumin test are 3.5 to 5.0 grams per deciliter. Normal levels for bilirubin are 0.1 to 1.0 milligrams per deciliter.
The Risks of a Liver Function Test
Blood draws are routine procedures and rarely cause any serious side effects. However, risks of giving a blood sample include:
- bleeding under the skin (hematoma)
- excessive bleeding