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Liver
Alanine aminotransferase (ALT)
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This is the date the draft was written, not a medical review date.
A cytosolic enzyme found mainly in hepatocytes, released when liver cells are injured. It is the most liver-specific of the routine aminotransferases.
Reference interval
| Conventional (U/L) | SI (U/L) | |
|---|---|---|
| Adults | 10–40 U/L | 10–40 U/L |
Specimen: Serum or heparinised plasma · Conventional × 1 = SI
Causes of high values
Viral and autoimmune hepatitis, alcohol-related and non-alcoholic fatty liver disease, drug-induced liver injury, ischaemic hepatitis, haemochromatosis, Wilson disease. Marked elevations (more than 10 times the upper limit) suggest acute hepatocellular injury.
Causes of low values
Low values are usually not clinically significant. Low activity can occur in pyridoxine (vitamin B6) deficiency and in advanced chronic kidney disease.
Pre-analytical and method notes
Upper limits are often lower in healthy women than in men (commonly about 35 versus 40 U/L), and some laboratories use lower cut-offs. Strenuous exercise and haemolysis can raise values slightly; the SI expression is sometimes microkatal per litre. Reference intervals vary by laboratory, method and population; use the interval printed on the report.
References
- Rifai N, Horvath AR, Wittwer CT. Tietz Textbook of Clinical Chemistry and Molecular Diagnostics. Elsevier, 6th edition (2018) — Tier 3 (textbook)
- McPherson RA, Pincus MR. Henry's Clinical Diagnosis and Management by Laboratory Methods. Elsevier — Tier 3 (textbook)
- Loscalzo J, et al.. Harrison's Principles of Internal Medicine. McGraw-Hill, 21st edition (2022) — Tier 3 (textbook)
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