Last Updated on July 28, 2022 by Dr. Neeraj Gujar
Table of Contents
Overview
Liver function tests (also known as liver chemistries) are used to determine the health and condition of your liver. They measure the levels of liver enzymes, proteins, and bilirubin within your blood. They can monitor or treat an existing condition. The test can reveal if your liver is displaying abnormally high or low levels of certain enzymes and proteins.
A variety of reasons liver function tests might be required include screening for hepatitis and monitoring side effects of medications and also determining the severity of liver disease.
A liver function testing is one among a number of tests that checks levels of enzymes and other protein in your blood. Some tests only look for enzymes that are present in the blood if your liver has been damaged or is suffering from a disease. Other tests verify that the organ functions as it should.
Your liver is responsible for many important functions that are vital to your health. It is responsible for breaking down food, making proteins and storing energy. You might experience a variety of symptoms, including yellow skin and slurred speech. This is when you may need to have a liver test.
When To Get Test Done?
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, especially if it’s suspected you were exposed to a virus that causes hepatitis
- If you already have liver disease, to monitor the disease and how well a particular treatment is working
- If you drink alcohol frequently
- To monitor the side effects of certain medications because some medications are known to affect the liver, including:
- NSAIDS
- Antibiotics
- Statins
- Tuberculosis drugs
- Antiseizure medications
- If you’re experiencing the symptoms of a liver disorder or have a family history of a liver disease, such as fatty liver disease
- If you have certain medical conditions, such as:
- High triglycerides
- High blood pressure
- Diabetes
- Anemia
- If you have gallbladder disease
Certain tests can reflect different aspects of liver function. For example, elevated alanine transaminase and aspartate transaminase disproportional to bilirubin and alkaline phosphatase levels often indicates liver disease.
You might have this test to check for a liver disease such as hepatitis (an illness in which your liver swells and can cause serious issues).
General symptoms of liver problems include:
- Lack of appetite
- Dark urine or light-colored poop (less common)
- Yellowish eyes or skin (jaundice)
- Swelling in your belly (less common)
- Nausea or vomiting
- Weakness or feeling very tired
Often, however, you don’t notice any symptoms.
Your doctor may order a liver test if you’re more likely to have liver damage or disease, like if you:
- Drink heavily or have an alcohol use disorder
- Have gallbladder disease or anemia
- Are very overweight, especially if you also have diabetes or high blood pressure
- Have a family member with liver disease
- Take medicine that can harm your liver
The liver test can also help your doctor learn whether an illness is getting worse or how well treatment is working.
What are the different types of liver function tests?
To measure the levels of specific enzymes or proteins in your blood, liver function tests can be used.
Atypical liver test results usually require a follow up to determine the reason for the abnormalities. Even mildly elevated results could indicate liver disease.
The following are common tests for liver function:
Alanine transaminase (ALT) test
The body uses Alanine Transaminase to metabolize proteins. ALT can be released into your bloodstream if the liver is not working properly or damaged. This can cause ALT levels to rise. This can indicate liver damage if the test returns a higher result than usual. An estimated 10% Americans have high ALT levels.
Aspartate aminotransferase (AST) test
Aspartate aminotransferase is an enzyme that can be found in many parts of your body.
- Heart
- Brain
- Pancreas
- Liver
- Muscles
AST can be released into your bloodstream when the liver is damaged. An abnormally high AST test result could indicate a problem in the liver or the muscles.
AST is not as precise as ALT in indicating liver damage. Therefore, it is often measured with ALT to determine if there are any liver problems. A high AST/ALT ratio could indicate alcoholic liver disease.
Test for Alkaline Phosphatase (ALP)
ALP (alkaline phosphatase) is an enzyme that can be found in your bones and bile ducts. A combination of several tests is often required to order an ALP test. A test that measures the bile ducts in the liver can be performed by ALP.
Albumin Test
Albumin, the main protein produced by your liver. It plays many important functions in your body. It nourishes your tissues, transports hormones and vitamins throughout your body. A test for albumin measures the amount of this protein your liver makes.
Bilirubin, a byproduct of the breaking down of red cells, is a waste product. The liver normally processes it. It is processed by the liver and excreted through your stool.
A damaged liver cannot properly process bilirubin. This causes a high level of blood bilirubin. Even though the liver functions are normal, certain inherited diseases can increase bilirubin levels.
Gamma-glutamyl Transferase (GGT) test
GGT enzyme levels above a certain level could indicate liver or bile damage.
L-lactate dehydrogenase (LD) test
LD can also be elevated in liver damage. However, it can also increase in other conditions.
Prothrombin Time (PT) test
This test measures the time it takes for your blood to clot. It could indicate liver damage if it takes longer than normal. Medications which thin your blood, like warfarin or Coumadin can also cause a longer PT. This test will not be performed unless you have had additional liver tests.
Also Read: Top 9 Annual Blood Tests to Keep You Healthy and Active
How To Get Tested?
Once your doctor recommends it, you can either get the test done at lab or book a home visit for sample collection.
Before the Test
Your doctor will provide detailed instructions about how to prepare for the part of the test that involves submitting blood samples.
Some medications and certain foods can affect the levels of these enzymes or proteins in your blood. You may be asked by your doctor to stop taking certain medications or to avoid certain foods for a time period before the test. Drink water throughout the testing period. Your doctor should be informed about all medications you take, including any over-the-counter or herbal supplements. You may be asked to stop eating the night before your test.
A shirt that has sleeves that can be easily rolled up may be the best option to help the medical professional collect your blood sample.
During the Test
Your blood may be drawn at a hospital or specialized testing facility.
To reduce the possibility of infection, the healthcare technician will wash your skin. The elastic strap will be wrapped around your arm. This will make your veins more visible. Then, they’ll use a needle and take blood samples from your arm. A thin needle is used by your doctor to draw a small amount blood. This usually happens from your elbow. The needle will cause a sensation of pinching or stinging. The technician will apply gauze and a bandage to the puncture site after the draw. The laboratory will test your blood.
These tests will likely be repeated several times over the course of a few days, or even weeks. To be certain of your condition, your doctor will examine the levels. You can receive your results within a few hours if you go to a clinic with a lab. It might take several days if it is not.
After The Test
Blood draws are routine procedures and rarely cause any serious side effects. However, the risks of giving a blood sample can include:
- Fainting
- Excessive bleeding
- Bleeding under the skin, or hematoma
- Infection
Test Results
The results will usually include normal values for that test. Remember that the normal results can be affected by different labs. It also depends on your gender.
A liver test by itself cannot tell you if you have a specific illness. Your doctor will help you interpret your results.
Below is a table that shows the results of liver function tests. It includes higher and lower than average results. Talk to your doctor after any liver function test. Discuss your results with him.
| Liver test | Indications | Typical and atypical ranges |
| ALT test | A higher result than typical on this test can be a sign of liver damage. Very high levels over 1,000 units per liter (U/L) are most often caused by viral hepatitis, ischemic hepatitis, or injury from drugs or other chemicals. | An ALT above 25 international units per liter (IU/L) in females and 33 IU/L in males typically requires further testing and evaluation. |
| Bilirubin test | A high result on the bilirubin test may indicate that the liver isn’t functioning properly. Elevated bilirubin levels with elevated ALT or AST may suggest cirrhosis or hepatitis. | The typical range for total bilirubin is usually 0.1–1.2 milligrams per deciliter (mg/dL). |
| Albumin test | A low result on this test can indicate that your liver isn’t functioning properly. This occurs in diseases such as cirrhosis, malnutrition, and cancer. | The typical range for albumin is 35–50 grams per liter (g/L). However, low albumin can also be a result of poor nutrition, kidney disease, infection, and inflammation. |
| AST test | A high result on an AST test might indicate a problem with your liver or muscles. Elevated AST without elevated ALT may indicate heart or muscle disease. If ALT, bilirubin, and ALP are also elevated, it may indicate liver damage. | The typical range for AST is usually up to 36 U/L in adults and may be higher in infants and young children. |
| ALP test | High levels of ALP may indicate liver inflammation, blockage of the bile ducts, or bone disease. | Children and adolescents may have elevated levels of ALPTrusted Source because their bones are growing. Pregnancy can also raise ALP levels. The typical range for ALP in adults is usually 20–140 IU/L. |
Also Read: How Do Doctors Use Renal Function Test to Diagnose Kidney Diseases
What To Do in Case of High Levels?
You can resume your normal activities almost immediately after the test. You should take a break if you feel lightheaded or faint during the blood draw.
These tests might not reveal to your doctor the exact condition or extent of your liver damage. However, they may help guide your doctor in the next steps. The results will be discussed at a follow up appointment or called by your doctor.
If your tests indicate that your liver function is impaired, your doctor will examine your medication history and review your medical history to determine the cause.
Additional diagnostic tests
Your doctor might decide to test for Hepatitis or other infections. You may also be offered imaging tests such as an ultrasound, or CT scanner. They may also recommend a liver biopsy in order to assess the liver for fibrosis or other liver conditions.
Coffee, tea, berries, grapefruit, grapes and cruciferous vegetables are some of the foods which are good for liver.
Jaundice, pale stool, dark colored urine, nausea, fluid retention, chronic fatigue are some major warning signs of failing liver.
Balanced diet, exercise will help lower the stress on liver. Avoid taking excessive medications, drugs, alcohol and drink plenty of water that can keep your liver healthy.
Sources
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medlineplus.gov/lab-tests/ast-test/ - Kwo PY, et al. (2017). ACG clinical guideline: Evaluation of abnormal liver chemistries.
journals.lww.com/ajg/fulltext/2017/01000/acg_clinical_guideline__evaluation_of_abnormal.13.aspx - Hall P, et al. (2012). What is the real function of the liver ‘function’ tests?
ncbi.nlm.nih.gov/labs/pmc/articles/PMC3609680/ - Lab test interpretation table. (n.d.).
bccancer.bc.ca/pharmacy-site/Documents/Clinical%20Pharmacy%20Guide/cpg3e-lab-test-table.pdf - Lowe D, et al. (2021). Alkaline phosphatase.
ncbi.nlm.nih.gov/books/NBK459201/ - Lala V, et al. (2021). Liver function tests.
ncbi.nlm.nih.gov/books/NBK482489/ - Robert C, et al. (2017). Mildly elevated liver transaminase levels: Causes and evaluation.
aafp.org/afp/2017/1201/p709.html - Sharma A, et al. (2021). Chronic liver disease.
ncbi.nlm.nih.gov/books/NBK554597/
