What is an ALT blood test? 

ALT, which stands for alanine transaminase, is an enzyme found mostly in the liver. When liver cells are damaged, they release ALT into the bloodstream. An ALT test measures the amount of ALT in the blood.  

High levels of ALT in the blood can indicate a liver problem, even before you have signs of liver disease, such as jaundice, a condition that causes your skin and eyes to turn yellow. An ALT blood test may be helpful in the early detection of liver disease. 

What is it used for? 

An ALT blood test is a type of liver function test. Liver function tests may be part of a regular checkup. You may have them done more frequently if you are on a biologic medication or other medication that may affect the liver. The test can also help diagnose liver problems. 

Why do I need an ALT blood test? 

Your health care provider may have ordered liver function tests, including an ALT blood test, as part of a routine exam or if you have symptoms of liver damage. These may include: 

• Nausea and vomiting 
• Jaundice 
• Abdominal pain 
• Loss of appetite 
• Unusual itching 
• Tiredness 

Because ALT in the bloodstream can indicate liver damage before symptoms appear, your health care provider may order an ALT blood test if you are at a higher risk for liver damage. Risk factors for liver disease include: 

• Family history of liver disease 
• Heavy drinking 
• Exposure or possible exposure to hepatitis virus 
• Obesity 
• Diabetes 
• Taking certain medicines that can cause liver damage 

What happens during an ALT blood test? 

A health care professional will take a blood sample from a vein in your arm, using a small needle. After the needle is inserted, a small amount of blood will be collected into a test tube or vial. You may feel a little sting when the needle goes in or out. This usually takes less than five minutes. 

Will I need to do anything to prepare for the test? 

You don’t need any special preparations for an ALT blood test. If your health care provider has ordered more tests on your blood sample, you may need to fast (not eat or drink) for several hours before the test. Your health care provider will let you know if there are any special instructions to follow. 

Are there any risks to the test? 

There is very little risk to having a blood test. You may have slight pain or bruising at the spot where the needle was put in, but most symptoms go away quickly. 

What do the results mean? 

An ALT blood test is often part of liver function testing. Liver function tests measure several different proteins, substances, and enzymes and can determine how well your liver is working. Your health care provider or Care Team may compare your ALT results with the results of other liver tests to help learn more about your liver function. High levels of ALT may indicate liver damage from hepatitis, infection, cirrhosis, liver cancer, or other liver diseases. 

Other factors, including medicines, can affect your results. Be sure to tell your health care provider about all the prescription and over-the-counter medicines you are taking. 

Is there anything else I need to know about an ALT blood test? 

ALT used to be called SGPT, which stands for serum glutamic-pyruvic transaminase. The ALT blood test was formerly known as the SGPT test. 

Source: MedlinePlus, National Library of Medicine