Alanine aminotransferase – ALT

What Is Alanine Aminotransferase?

Alanine aminotransferase (ALT) is an enzyme found mainly in liver cells (hepatocytes). It is a cytoplasmic enzyme involved in protein metabolism, and its concentration in the blood is usually low.

ALT Level Test

The ALT laboratory test is performed using a blood sample to determine the level of alanine aminotransferase. The test involves drawing blood from a vein, which is then sent to the laboratory for analysis. During the procedure, blood is collected into an EDTA tube according to standard collection protocol. The entire process takes only a few minutes. Improper preparation for the test may lead to unreliable results. Blood should be collected in the morning.

Increased ALT activity indicates damage to liver cells. Aminotransferases are found in the liver, heart, and skeletal muscles. If ALT levels in the blood serum are elevated, this may indicate damage to hepatocytes or myocytes.

When Should You Perform an ALT Blood Test?

An ALT test is recommended when symptoms suggesting liver problems occur, such as:

• yellowing of the skin and mucous membranes,
• dark-colored urine,
• pale stools,
• nausea and vomiting,
• pain in the right upper abdomen,
• chronic fatigue.

Adults should perform an ALT test at least once a year, even in the absence of symptoms, to monitor liver health. This is especially important for people in high-risk groups, such as individuals who consume excessive alcohol, patients with obesity, and those taking medications that affect the liver (e.g., statins, oral contraceptives).

What Does the Test Diagnose?

Elevated ALT

Elevated ALT levels may indicate liver damage and may result from various conditions, such as:

• acute and chronic viral hepatitis (hepatitis A, B, C),
• fatty liver disease,
• toxic liver damage (e.g., due to medications or alcohol),
• liver cirrhosis,
• Wilson’s disease,
• acute liver ischemia.

Low ALT

Low ALT levels are usually less concerning than elevated levels. They may occur in situations such as:

• kidney failure,
• vitamin B6 deficiency,
• pregnancy (a natural decrease in enzyme activity may occur).

Low ALT values are often considered normal and do not require medical intervention unless accompanied by other symptoms.

Learn more:

• Fatty liver — symptoms, causes, diet
• HCV virus – infection, hepatitis symptoms, and diagnosis of hepatitis C
• Chronic fatigue and lack of energy — causes, symptoms, and treatment

How to Prepare for an ALT Test?

• The patient should be fasting — this means avoiding food and beverages such as coffee or tea for about 12 hours before the test. In the morning, only water is allowed, up to one glass.
• It is not recommended to consume alcohol 2–3 days before the test.
• If possible, the blood sample should be taken before the morning dose of medication, unless otherwise advised by a doctor. Ideally, blood should be collected in the morning, usually between 7:00 and 10:00.
• The patient should rest for 10–15 minutes before the blood draw.

Alanine Aminotransferase – Reference Ranges

The normal level of alanine aminotransferase (ALT) should not exceed 35–40 IU/l, specifically:

• the upper limit for men is 30 IU/l,
• the upper limit for women is 19 IU/l.

These values may vary depending on the laboratory, so it is always important to refer to the specific reference ranges provided by the testing facility.

ALT Test Result

In the case of abnormal results, consultation with a doctor is recommended for proper interpretation. ALT levels should be assessed in conjunction with other tests, such as aspartate aminotransferase (AST).

The ratio of AST to ALT (the de Ritis ratio) provides additional diagnostic information. For example, an AST/ALT ratio greater than 2 may suggest alcohol-related liver damage.

When interpreting the results, the doctor will also consider the patient’s medical history and the presence of clinical symptoms such as jaundice, fatigue, or abdominal pain to provide a more accurate assessment.

More information on how to access your test results can be found HERE >>

Factors That May Affect Test Results

• use of certain medications,
• alcohol.

Who Should You Consult About Abnormal Results?

• Gastroenterologist
• Internist