AST (Aspartate Transaminase) is a blood test that measures ast (aspartate transaminase) levels in the blood. Normal range: Men: < 40 U/L · Women: < 35 U/L (typical Australian pathology reference range). It is commonly used to aST complements ALT in assessing liver damage. The AST/ALT ratio (De Ritis ratio) is a well-established diagnostic tool:...
What is AST (Aspartate Transaminase)?
AST (Aspartate Transaminase, also written ASAT or SGOT) is an enzyme found in the liver, heart, skeletal muscle and red blood cells. Because AST exists in multiple tissues, it is less liver-specific than ALT. Pathology labs report AST as part of the standard Liver Function Test (LFT) panel.
Why is it measured?
AST complements ALT in assessing liver damage. The AST/ALT ratio (De Ritis ratio) is a well-established diagnostic tool: a ratio >2 is strongly suggestive of alcoholic liver disease, a ratio <1 suggests non-alcoholic fatty liver disease (NAFLD), and a very high AST with normal ALT can indicate muscle injury, rhabdomyolysis or a recent heart attack. AST is included in every routine LFT ordered in Australia.
Normal Reference Range
Men: < 40 U/L · Women: < 35 U/L (typical Australian pathology reference range)
Note: Reference ranges may vary between laboratories. Always consult your healthcare provider for interpretation.
What Causes High AST?
High AST signals damage to any tissue containing the enzyme — most commonly the liver, but also heart, skeletal muscle or red blood cells. Liver causes mirror those of high ALT: NAFLD, alcohol-related disease, viral hepatitis and drug-induced injury. AST disproportionately higher than ALT (ratio >2) is a classic sign of alcoholic liver disease. AST that is markedly elevated with a normal ALT often points away from the liver: rhabdomyolysis, recent heart attack, vigorous exercise, or haemolysis (red blood cell breakdown). In Australia, AST elevations should be interpreted alongside CK (for muscle injury) and troponin (for cardiac injury) when the pattern is non-hepatic.
What Causes Low AST?
Low AST is rarely clinically meaningful. It can be seen with vitamin B6 (pyridoxine) deficiency, chronic kidney disease, and during pregnancy. A low AST does not rule out underlying liver disease and should be interpreted alongside ALT, GGT, and the rest of the LFT panel.
How Often Should AST Be Tested?
AST is part of the standard LFT panel ordered annually in routine health checks, every 6 months for patients with metabolic risk factors, and every 3–6 months for anyone on TRT, anabolic steroids, or hepatotoxic medication. Athletes and weightlifters should note that intense training in the days before a blood draw can transiently raise AST without indicating liver disease.
Related Blood Markers
Always interpreted alongside ALT (the AST/ALT ratio is diagnostically important), GGT, ALP, bilirubin and CK when muscle injury is suspected.
Key Facts
- •Category: Vital Organ Functions
- •Unit of Measurement: U/L
- •Test Code: AST
Related Vital Organ Functions Markers
Albumin
The main protein in blood plasma, produced by the liver.
Learn moreALP (Alkaline Phosphatase)
An enzyme found primarily in the liver and bones.
Learn moreALT (Alanine Transaminase)
ALT (Alanine Transaminase, also written ALAT or SGPT) is an enzyme concentrated in the liver. When liver cells are damaged, ALT leaks into the bloodstream, so it is the single most liver-specific enzyme on a standard Liver Function Test (LFT). It is often interpreted alongside AST, GGT and ALP to build a picture of liver health.
Learn moreBilirubin
A yellow pigment produced during the breakdown of red blood cells.
Learn moreBUN (Blood Urea Nitrogen)
A waste product filtered by the kidneys.
Learn moreCreatinine
A waste product produced by muscles and filtered by the kidneys.
Learn more