AST
Also known as: Aspartate Aminotransferase, SGOT
What Does AST Measure?
AST (Aspartate Aminotransferase), also known as SGOT (Serum Glutamic-Oxaloacetic Transaminase), is an enzyme found primarily in the liver, heart, muscles, kidneys, and red blood cells. A blood test measures the amount of AST released into the bloodstream, which normally contains only small amounts of this enzyme. When cells in these organs are damaged or destroyed, they release AST into the blood, causing levels to rise.
Why Does AST Matter?
AST is most commonly used as a marker of liver health, often measured alongside ALT (Alanine Aminotransferase) to help detect and monitor liver disease, including hepatitis, cirrhosis, and liver damage caused by alcohol or medications. Because AST is also present in heart and muscle tissue, elevated levels can indicate heart attack, muscle disease, or other conditions beyond the liver. The AST/ALT ratio is a particularly useful diagnostic tool — a ratio greater than 2:1 often suggests alcoholic liver disease, while a ratio closer to 1:1 may point to non-alcoholic fatty liver disease or viral hepatitis. Regular monitoring of AST helps clinicians track disease progression and evaluate treatment effectiveness.
Normal Ranges
Males
10–40 U/L
Females
9–32 U/L
Children
Varies by age; typically 20–60 U/L in infants, decreasing to adult levels by adolescence
Causes of High Levels
- Liver disease or damage (hepatitis, cirrhosis, fatty liver disease)
- Excessive alcohol consumption or alcoholic liver disease
- Heart attack or acute cardiac injury
- Skeletal muscle injury, intense exercise, or rhabdomyolysis
- Certain medications and supplements (statins, acetaminophen overdose, some antibiotics)
- Thyroid disorders, particularly hypothyroidism
Causes of Low Levels
- Vitamin B6 (pyridoxine) deficiency, as AST requires B6 as a cofactor
- Chronic kidney disease or end-stage renal disease
- Pregnancy, especially in the second and third trimesters
- Uremia (high levels of urea in the blood)
How to Improve Your AST
Diet
- Eliminate or significantly reduce alcohol intake, as alcohol is a direct liver toxin
- Adopt a Mediterranean-style diet rich in vegetables, whole grains, legumes, and healthy fats like olive oil to support liver health
- Reduce intake of processed foods, refined sugars, and saturated fats to lower the risk of fatty liver disease
- Increase consumption of cruciferous vegetables (broccoli, Brussels sprouts, cauliflower) which support liver detoxification enzymes
- Stay well-hydrated with water and include coffee (2–3 cups/day), which has been shown in studies to lower liver enzyme levels
Supplements
- Milk thistle (silymarin) 140–420 mg daily — has antioxidant and anti-inflammatory properties that may protect liver cells
- Vitamin E 400–800 IU daily — shown in clinical trials to reduce liver inflammation in non-alcoholic steatohepatitis (NASH), consult a doctor first
- N-acetylcysteine (NAC) 600 mg twice daily — supports glutathione production and liver detoxification
- Vitamin B6 (pyridoxine) 10–25 mg daily if deficiency is suspected, as it is a required cofactor for AST activity
- Omega-3 fatty acids 2–4 g daily — may reduce liver fat and inflammation in fatty liver disease
Related Biomarkers
Frequently Asked Questions
What is a dangerously high AST level?
AST levels above 1,000 U/L are considered severely elevated and are often seen in acute conditions such as acetaminophen overdose, acute viral hepatitis, ischemic hepatitis (shock liver), or severe drug toxicity. Levels 3–10 times the upper limit of normal (roughly 100–400 U/L) are considered moderately elevated and warrant further investigation. Even mildly elevated levels (1–3 times normal) should not be ignored and should be evaluated in the context of other liver tests and symptoms.
Can exercise cause high AST levels?
Yes, intense physical exercise — particularly heavy weightlifting, long-distance running, or any activity causing significant muscle exertion — can temporarily raise AST levels because the enzyme is released from damaged muscle fibers. This elevation is usually mild to moderate and resolves within 24–72 hours after rest. If your AST is tested shortly after vigorous exercise, inform your doctor so results can be interpreted correctly. Persistent or significantly elevated AST warrants investigation even in active individuals.
What is the AST/ALT ratio and why does it matter?
The AST/ALT ratio compares the levels of two liver enzymes to help identify the likely cause of liver damage. A ratio above 2:1 (AST being more than twice as high as ALT) strongly suggests alcoholic liver disease. A ratio close to 1:1 is more typical of non-alcoholic fatty liver disease or viral hepatitis. When AST is much higher than ALT in the setting of normal liver function tests, heart or muscle damage should be considered. This ratio is a valuable diagnostic clue but must always be interpreted alongside other tests and clinical information.