Alt Blood Test

An ALT blood test measures alanine transaminase (ALT), an enzyme found mainly in the liver. It is also called an SGPT test, named for the older term serum glutamic-pyruvic transaminase. The test measures ALT from a blood sample and is commonly included among liver function tests to help assess possible liver injury or inflammation.

ALT is not a diagnosis by itself. Clinicians interpret the result alongside your symptoms, medical history, medicines, and other blood tests, such as AST, to understand what it may mean.

A clinician may order an ALT blood test when symptoms suggest a liver problem, such as yellowing of the skin or eyes (jaundice), dark urine, abdominal discomfort, unusual tiredness, or nausea. Testing may also be used when liver disease is suspected or when another examination raises concern about liver health.

ALT may also be checked to monitor medicines that can affect the liver, follow a known liver condition, or assess risk related to alcohol use or other health factors. It is often ordered together with a broader function liver test panel, including other liver function tests, rather than used alone.

Most ALT tests do not require special preparation. However, fasting may be requested if other blood tests are being collected at the same time, so follow the instructions from your clinician or laboratory.

Before an SGPT/ALT lab test, tell the healthcare professional about prescription medicines, over-the-counter medicines, supplements, alcohol use, and strenuous exercise when relevant. These details can help the clinician interpret the result accurately.

A healthcare professional cleans the skin, usually on the arm, and inserts a needle into a vein. They collect a small blood sample, remove the needle, and apply pressure and a bandage to the puncture site.

You may feel a brief pinch or stinging sensation when the needle enters or leaves the skin. An ALT blood test is a single blood-draw session, not continuous monitoring, and you can usually leave soon after the sample is collected.

ALT testing is generally low risk because it involves a routine blood draw. Possible short-term effects include brief pain or stinging, bruising, minor bleeding, soreness, or lightheadedness near the puncture site.

Your report gives an ALT value, usually in units per liter, along with the laboratory’s reference range. Reference ranges can differ between laboratories and may also vary with factors such as age, sex, and overall health, so use the range printed on your report.

What Can a High ALT Level Mean?

High ALT can occur with liver inflammation or injury, medicine effects, alcohol use, fatty liver disease, or certain infections. Strenuous exercise can also affect ALT in some people. A high ALT blood test does not identify a specific cause on its own, and one result should not be used to make a diagnosis.

Clinicians may compare ALT with AST, also called SGOT, along with symptoms, medical history, and other liver function tests. The importance of an elevated result depends on how high it is, whether symptoms are present, and the overall clinical context. If you have questions about high ALT, ask the clinician who ordered the test when to worry about ALT levels and whether follow-up testing is needed.