[Durgical](https://durgical.com/en/) › [DurgiPedia](https://durgical.com/en/durgipedia/) › [Biochemistry](https://durgical.com/en/biochemistry/) › Aminotransferases (ALT and AST) as lab tests [Biochemistry](https://durgical.com/en/biochemistry/) · Topic # Aminotransferases (ALT and AST) as lab tests ALT and AST leak into the blood when liver cells break; ALT is liver-specific, AST also comes from muscle. Updated 2026-11-01 ## Key facts - ALT (SGPT) is cytosolic and almost exclusive to the liver: it is the most specific marker of hepatocellular injury. - AST (SGOT) is in the cytosol and mitochondria of liver, heart, skeletal muscle, kidney and red cells: it is less specific. - AST/ALT ratio > 2 suggests alcohol-related liver disease (alcohol depletes pyridoxine and injures mitochondria); in viral hepatitis and fatty liver ALT is usually higher. - Both use pyridoxal phosphate (vitamin B6) as a cofactor. - Their reference range varies by laboratory, sex and age. ## In detail - What they measure: the catalytic activity of two enzymes that transfer amino groups (alanine ⇄ pyruvate; aspartate ⇄ oxaloacetate), with glutamate and α-ketoglutarate as the partner pair. - Where they come from: ALT from the hepatocyte cytosol; AST also from mitochondria, myocardium and muscle. The blood half-life is longer for ALT (about 2 days) than for AST (under 1 day). - Why they rise a little (under 5 times the limit): metabolic dysfunction-associated fatty liver, alcohol, chronic hepatitis B or C, drugs, haemochromatosis, coeliac disease. - Why they rise a lot (hundreds to thousands): acute viral hepatitis, paracetamol, ischaemic hepatitis, autoimmune hepatitis, early acute biliary obstruction by a stone. - Pitfalls: hard exercise, rhabdomyolysis and hypothyroidism raise AST (and some ALT) without liver injury; a haemolysed sample raises AST; B6 deficiency (alcohol, dialysis) can give falsely low values. - A mild isolated rise is repeated and read against the history (alcohol, drugs, weight) before larger work-ups. **Also called** SGPT and SGOT, Serum transaminases, AST/ALT ratio ## Clinical notes - In ischaemic hepatitis aminotransferases reach thousands within 24–48 hours and fall fast; in viral hepatitis they fall more slowly. - High AST with high CK suggests a muscle source, not the liver. - In Wilson disease, a low alkaline phosphatase with high aminotransferases and haemolysis is a classic clue. ## Related conditions - [Viral hepatitis](https://durgical.com/en/conditions/viral-hepatitis/) - [Cirrhosis](https://durgical.com/en/conditions/cirrhosis/) - [Myocardial Infarction (Heart Attack)](https://durgical.com/en/conditions/myocardial-infarction/) - [Wilson disease](https://durgical.com/en/conditions/wilson-disease/) - [Hereditary hemochromatosis](https://durgical.com/en/conditions/hereditary-hemochromatosis/) ## Related - [Alanine aminotransferase (ALT, GPT)](https://durgical.com/en/biochemistry/enzymes/alanine-aminotransferase/) - [Aspartate aminotransferase (AST, GOT)](https://durgical.com/en/biochemistry/enzymes/aspartate-aminotransferase/) - [Liver function tests: reading the pattern](https://durgical.com/en/biochemistry/topics/liver-function-tests-reading-the-pattern/) - [Transamination and deamination](https://durgical.com/en/biochemistry/topics/transamination-and-deamination/) - [Vitamin B6 (pyridoxal phosphate)](https://durgical.com/en/biochemistry/molecules/vitamin-b6/) ## Test yourself Think of the answer, then tap the question to see it. ## Which aminotransferase is more liver-specific? ALT (SGPT): it is cytosolic and almost exclusive to hepatocytes; AST is also in heart, muscle and red cells. ## What does an AST/ALT ratio above 2 suggest? Alcohol-related liver disease: alcohol depletes vitamin B6 (lowering ALT more) and injures mitochondria (releasing mitochondrial AST). ## What raises aminotransferases into the thousands? Acute viral hepatitis, paracetamol poisoning, ischaemic hepatitis and autoimmune hepatitis. ## Why is a high AST not always hepatic? AST also leaks from muscle, heart and red cells: rhabdomyolysis, hard exercise or haemolysis raise it. [Add to my cards (4)](https://durgical.app/estudiar/?add=/en/biochemistry/topics/aminotransferases-as-lab-tests/) Educational information, not medical advice. For any symptom, see a health professional. Sources: [ALT Blood Test: MedlinePlus Medical Test](https://medlineplus.gov/lab-tests/alt-blood-test/) (MedlinePlus, US National Library of Medicine, 2026); [AST Test: MedlinePlus Medical Test](https://medlineplus.gov/lab-tests/ast-test/) (MedlinePlus, US National Library of Medicine, 2026); [Alanine transaminase (ALT) blood test: MedlinePlus Medical Encyclopedia](https://medlineplus.gov/ency/article/003473.htm) (MedlinePlus, US National Library of Medicine, 2026); [Aspartate aminotransferase (AST) blood test: MedlinePlus Medical Encyclopedia](https://medlineplus.gov/ency/article/003472.htm) (MedlinePlus, US National Library of Medicine, 2026); Textbook of Biochemistry for Medical Students, 6th ed. (Jaypee Brothers Medical Publishers (Vasudevan DM, Sreekumari S, Vaidyanathan K), 2011). [← All of biochemistry](https://durgical.com/en/biochemistry/) ## **Spotted a mistake?** We are always improving for the community. Tell us what is wrong and our team will review it. 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