Alanine aminotransferase (ALT)

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Latest Edit: Iva Lloyd, ND 2021-08-24 (EDT)

See Also Lab Tests

Alanine aminotransferase, also known as ALT or SGPT (serum glutamic-pyruvic transaminase), is an enzyme present primarily in the liver, but it is also present in skeletal muscle, the heart and the kidneys. ALT levels increase in the blood following cell damage or destruction. This test is used to assess and monitor hepatocellular diseases of the liver.[1], [2]


  • Alanine aminotransferase is the enzyme that catalyzes the conversion of the amino acid L-alanine and α-keto-glutarate into pyruvate and L-glutamate, hence the older name SGPT or Serum Glutamate-Pyruvate Transaminase.
  • ALT is functionally similar to AST, yet increases faster than AST in response to cellular damage. AST exists in the cytosol and the mitochondria of the hepatocyte, whereas ALT only exists in the cytosol.
  • ALT is more specific for the detecting liver damage than cardiovascular disease.
  • ALT levels take a long time to normalize after an elevation.

Patient Preparation

Fasting is not required for this test.

  • Factors which can cause increased levels:
  • Drugs: previous IM injections, acetaminophen, allopurinol, aminosalicylic acid, ampicillin, azathioprine, carbamazepine, cephalosporins, chlordiazepoxide, chlorpropamide, clofibrate, cloxacillin, codeine, dicumarol, indomethacin, isoniazid, methotrexate, methyldopa, nafcillin, nalidixic acid, nitrofurantoin, oral contraceptives, oxacillin, phenothiazines, phenlbutazone, phenytoin, procainamide, propoxyphene, propranolol, quinidine, salicylates, tetracyclines, and verapamil.
  • Exercise: strenuous exercise

Clinical Implications

Ranges: The following are the reference ranges for this lab. However, lab ranges can vary by laboratory and country. [2]

Standard U.S. Units (U/L) Standard International Units (U/L)
Conventional Laboratory Range 0 - 45 0 - 45
Optimal Range 10 - 30 10 - 30
Alarm Ranges > 100 > 100

High levels indicate:

Moderately increased levels:

  • Obesity
  • Cirrhosis
  • Cholestasis
  • Hepatic tumor
  • Hepatotoxic drugs
  • Obstructive jaundice
  • Severe burns
  • Trauma to striated muscle

Mildly increased levels indicate:


Associated Tests


  1. Pagana Kathleen D, Pagana Timothy J (2006) Mosby's Manual of Diagnostic and Laboratory Tests, Mosby.
  2. 2.0 2.1 Weatherby Dicken, Ferguson Scott (2002) Blood Chemistry and CBC Analysis: Clinical Laboratory Testing from a Functional Perspective, Bear Mountain.