Alanine Aminotransferase

What It Is, Indications for Testing, Interpretation, and More

Author: Emily Miao, PharmD, MD

Editor: Alyssa Haag, MD

Editor: Józia McGowan, DO

Editor: Kelse LaFayette, DNP, ARNP, FNP-C

Illustrator: Abbey Richard, MSc

Modified: May 14, 2025

What is alanine aminotransferase?

Alanine aminotransferase (ALT), also known as alanine transaminase and serum glutamic pyruvic transaminase (SGPT), is an enzyme found in the liver and kidneys, that is primarily responsible for amino acid degradation and gluconeogenesis (i.e., a biochemical process that allows the body to form glucose from certain precursors such as lactate and glucogenic amino acids) within the body. In gluconeogenesis, ALT helps convert important citric acid cycle substrates like alpha-ketoglutarate into pyruvate and glutamate, which are then used to regenerate glucose for the body.

An infographic detailing alanine aminotransferase.

How are alanine aminotransferase levels evaluated?

Serum ALT is often evaluated in conjunction with another liver enzyme called aspartate aminotransferase (AST), also referred to as serum glutamic-oxaloacetic transaminase (SGOT). ALT and AST are also known as liver enzymes found in the blood and they are routinely drawn within a comprehensive metabolic panel (i.e., basic chemistry labs plus liver enzymes) in order to assess for liver injury. Serum ALT samples are drawn from venous blood and the test measures the amount of ALT in a blood sample. The reference range or normal amount of ALT in the blood varies but is typically 7 to 56 units per liter (U/L). ALT levels are also higher in genetic males compared to genetic females at baseline. Sometimes, ALT and AST are evaluated along with laboratory tests that may be part of a liver panel. The liver panel also includes other tests like indirect and direct bilirubin and alkaline phosphatase, which are adjunct tests to help evaluate liver function.

What are indications for evaluating alanine aminotransferase?

Liver enzymes, such as ALT, are often evaluated in the setting of evaluating or monitoring liver disease or liver function. If there is clinical suspicion that the liver may not be functioning properly or may be damaged, liver function tests and liver enzymes may be ordered for further evaluation. Conditions that can affect liver function and may require further evaluation with serum ALT include chronic liver disease (e.g., non-alcoholic fatty liver disease), liver cancer, toxin-induced liver injury (e.g., from alcohol, acetaminophen), and infectious diseases (e.g., hepatitis). Clinical signs of impaired liver function include jaundice (i.e., yellowing of the skin and/or eyes) and dark yellow urine. Other non-specific signs and symptoms may include unexplained weight loss or fatigue, abdominal pain, and an enlarged liver on an abdominal exam.

What does an elevated alanine aminotransferase indicate?

Since liver enzymes like ALT and AST are primarily found within the liver, the presence of these enzymes in the blood may indicate liver damage. Acute liver diseases such as viral hepatitis or ischemic hepatitis may present with extremely high levels of ALT/AST (i.e., in the 1000s) with an ALT/AST ratio often greater than 2 with ALT typically greater than AST. Some medications that affect liver function such as oral tretinoin and daptomycin may also require ALT/AST monitoring to ensure levels are within a normal range. Rhabdomyolysis is a serious non-hepatic condition characterized by cardiac and/or skeletal muscle breakdown. This can occur secondary to intense exercise and may also result in increased ALT/AST levels due to increased muscle breakdown.

What does a decreased alanine aminotransferase indicate?

Test results showing a decreased amount of ALT are less common when compared to tests showing a high level of ALT. A decreased amount of ALT may be associated with aging or sarcopenia (i.e., an age-related, involuntary loss of skeletal muscle mass). Some studies have also noted correlations between low ALT levels (e.g., <16 international units per liter [IU/L]) and long-term mortality in certain populations (e.g., patients with chronic kidney disease and patients with heart disease).

What are the most important facts to know about alanine aminotransferase?

Alanine aminotransferase (ALT), also known as alanine transaminase, is an enzyme that is found in the liver and kidneys. ALT is primarily responsible for amino acid degradation and gluconeogenesis. Serum ALT is often evaluated in conjunction with another liver enzyme called aspartate aminotransferase (AST). Liver enzymes which include ALT are often evaluated in the setting of evaluating or monitoring liver disease or liver function. Since liver enzymes like ALT and AST are primarily found within the liver, the increased levels of these enzymes in the blood may indicate a spillage of enzymes, suggestive of liver damage. Test results showing a decreased amount of ALT may be associated with aging and sarcopenia.

References

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Kaplan MM. Alanine aminotransferase levels: what's normal? Ann Intern Med. 2002;137(1):49-51. doi:10.7326/0003-4819-137-1-200207020-00012

Nonalcoholic fatty liver disease: common questions and answers on diagnosis and management. Am Fam Physician. 2020;102(9):603-612. https://www.aafp.org/pubs/afp/issues/2020/1115/p603.html

Peltz-Sinvani N, Klempfner R, Ramaty E, et al. Low ALT levels independently associated with 22-year all-cause mortality among coronary heart disease patients. J Gen Intern Med. 2016;31(2):209-214. doi:10.1007/s11606-015-3480-6

Saito Y, Okumura Y, Nagashima K, et al. Low alanine aminotransferase levels are independently associated with mortality risk in patients with atrial fibrillation. Sci Rep. 2022;12(1):12183. doi:10.1038/s41598-022-16435-5

Schindhelm RK, Diamant M, Dekker JM, Tushuizen ME, Teerlink T, Heine RJ. Alanine aminotransferase as a marker of non-alcoholic fatty liver disease in relation to type 2 diabetes mellitus and cardiovascular disease. Diabetes Metab Res Rev. 2006;22(6):437-443. doi:10.1002/dmrr.666

Senior JR. Alanine aminotransferase: a clinical and regulatory tool for detecting liver injury—Past, present, and future. Clin Pharmacol Ther. 2012;92(3):332-339. doi:10.1038/clpt.2012.108

Sherman KE. Alanine aminotransferase in clinical practice. A review. Arch Intern Med. 1991;151(2):260-265.