Aspartate Aminotransferase (AST)
An enzyme found mainly in the liver, and also in muscle and heart. Raised blood levels can be a sign of damage to those cells.
AI-verified against cited sources. Awaiting expert reviewAlso called AST, SGOT, GOTLOINC 1920-8
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The usual range for AST depends on sex. Choose female or male above to see where you stand.
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What it is
Aspartate aminotransferase (AST), also called SGOT, is an enzyme that helps your cells process amino acids. It is found mostly in the liver, but also in heart and skeletal muscle, kidneys, brain and red blood cells. Healthy people have low levels in the blood. When these cells are damaged, AST leaks out and the blood level rises. AST clears from the blood fairly quickly, with a half-life of about 17 hours, so a high level usually reflects recent damage.
Why it matters
AST is part of routine liver checks and is usually read together with ALT. A high AST can be a sign of liver cell injury. Because AST also comes from muscle and heart, it is less specific to the liver than ALT. A normal AST doesn't rule out liver disease either, since levels can be normal even in long-standing liver conditions. Your clinician looks at the whole pattern, including the AST-to-ALT ratio and your other liver tests.
If it’s low
A low AST is usually considered normal and rarely matters on its own.
Common causes
- Vitamin B6 deficiency
- Kidney failure (uremia), in some people
- Some medicines, such as metronidazole
What can help
- A low AST on its own usually needs no follow-up. You can mention it to your clinician if it comes with symptoms or other unusual results.
If it’s high
A level above your lab's range has many possible explanations. Hard exercise or a muscle strain is a common and harmless one. Liver-related causes include fatty liver disease, alcohol, viral hepatitis and medicines. How high the result is, and what your other liver tests show, help narrow it down.
Common causes
- Strenuous exercise or a muscle injury
- A blood sample in which red blood cells broke open (hemolysis)
- Fatty liver disease, a common cause of mild rises
- Alcohol use
- Medicines, herbal products and supplements that affect the liver
- Viral hepatitis and other liver inflammation
- Heart or muscle conditions, including a heart attack, muscle inflammation or muscular dystrophy
- Less often, celiac disease, iron overload (hemochromatosis) or autoimmune hepatitis
- Macro-AST, a harmless condition in which AST binds to other proteins and clears slowly
What can help
- Ask your clinician whether it makes sense to repeat the test after a few days of rest from hard exercise
- Review your medicines, supplements and herbal products with your clinician
- If fatty liver or alcohol might be involved, ask about lifestyle steps that support liver health, such as limiting alcohol and keeping a healthy weight
- Ask whether ALT, GGT or a muscle enzyme test (CK) could show where the AST is coming from
Usual ranges
What labs print as the reference range, by who was tested. Ranges differ a little between labs, so the range on your own report is the one your result is judged against.
The usual range depends on sex and age. Choose women or men to see the one that applies.
- Men, 14+8–48 U/L
Sources: Mayo Clinic Laboratories, Labcorp, American Board of Internal Medicine
- Women, 14+8–43 U/L
Sources: Mayo Clinic Laboratories, Labcorp, American Board of Internal Medicine
Children and teens 2 ranges
- Men, 1–138–60 U/L
Sources: Mayo Clinic Laboratories, Labcorp
- Women, 1–138–50 U/L
Sources: Mayo Clinic Laboratories, Labcorp
See AST by age and sex, with the U.S. survey numbers where they exist.
If this applies to you
AST means a little more for some people. Open the one that fits you.
Hemochromatosis or iron overload
AST is read with ALT. ACG notes that in people with two copies of C282Y, a ferritin above 1,000 ng/mL together with raised liver enzymes and a low platelet count is strongly linked to cirrhosis, which is why these are looked at together when the condition is found.
Fatty liver or liver condition
AST is read with ALT and goes into the FIB-4 score. BSG notes that an AST higher than ALT can point to advanced scarring, and that this ratio stays useful even when both are in the usual range.
Strength training
AST is found in muscle as well as liver. In one study, a single hour of weightlifting raised AST in men new to lifting, while GGT and bilirubin stayed normal.
Taking isotretinoin
AST often sits on the same liver panel as ALT. Hard workouts can raise AST from muscle, which is worth knowing when liver tests are checked on isotretinoin.
Taking methotrexate
AST is a liver enzyme often checked with ALT. The BSR accepts ALT, AST or both as the liver test, so which one appears on a report depends on the clinic.
How common is your level?
NHANES describes the US civilian, non-institutionalized population, not a 'healthy' reference group. People with disease, on medication, fasting or not (except fasting-subsample markers), smokers and so on are all included. A percentile says where a value sits among Americans of that sex and age, not whether it is normal.
Use the left and right arrow keys to read each age. Shift moves five years.
Reference data derived from CDC/NCHS National Health and Nutrition Examination Survey (NHANES), cycles 2015-2016, 2017-March 2020 (pre-pandemic), August 2021-August 2023. Analysis by bloodtesttracker.com; not endorsed by CDC, NCHS or HHS.
Explore AST by age and sex: every percentile as a table, with a download.
What can affect your result
- Sex and age: Mayo's adult upper limits are 48 U/L for men and 43 U/L for women, and children's limits are higher
- Exercise: strenuous exercise can raise AST
- Sample handling: hemolysis (broken red blood cells) can raise the result
- Alcohol, medicines and supplements
- Pregnancy can affect results
- Vitamin B6 status and the assay method
- Lab differences: Mayo prints 8–48 U/L for men and 8–43 for women, while Labcorp prints 0–40 IU/L for all adults
- Hard exercise or muscle injury can raise AST, because AST also comes from muscle.
- Red blood cells contain AST, so a sample where cells broke open (hemolysis) can read falsely high. Labs reject grossly hemolyzed samples (Labcorp, ARUP).
- Tubes with oxalate, fluoride, EDTA or citrate aren't suitable for this test (Labcorp, ARUP).
- Vitamin B6 deficiency can lower AST, and assays differ in whether pyridoxal-5'-phosphate (the active form of B6) is added.
- Alcohol, many medicines and some herbal products can raise AST.
- If other tests were ordered on the same draw, follow the fasting instructions for those tests.
Fast. Total AST has a half-life of about 17 hours, so after a one-time injury it usually falls back within days. Ongoing injury keeps it raised.
When to talk to a clinician
Contact the clinician who ordered the test promptly if your AST is 10 or more times your lab's upper limit, or above about 500 U/L (Labcorp notes that values above 500 usually point to hepatitis or another cause of significant liver cell injury), or if any raised AST comes with yellow skin or eyes, dark urine, pale stools, severe belly pain, repeated vomiting, confusion or unusual sleepiness. Call 911 or your local emergency number for chest pain, trouble breathing, confusion or fainting.
Questions you could ask
- How do my AST and ALT compare, and does the ratio matter for me?
- Which everyday factors, such as alcohol, exercise or medicines, could be affecting my liver tests?
- Could recent exercise, a medicine or a supplement explain this result?
- Should we check ALT, GGT or CK to see where the AST is coming from?
- Should we repeat it, and when?
- Is there any reason to follow up on a low AST?
Questions people ask
Why is my AST high but my ALT normal?
AST also comes from muscle, heart and red blood cells, while ALT is more specific to the liver. Hard exercise, a muscle injury, a sample with broken red blood cells, or a harmless macro-AST can raise AST alone. In alcohol-related liver injury AST is often higher than ALT as well. Your clinician can sort this out, and a CK test can check for a muscle source.
What does the AST-to-ALT ratio mean?
It compares the two liver enzymes. In adults, a ratio above 1 has been linked with more advanced liver scarring, and a ratio above 2 is often seen in alcohol-related liver disease. It is a clue to discuss with your clinician, not a diagnosis. We show it as its own marker.
Can exercise raise AST?
Yes. Strenuous exercise can raise both AST and ALT, and AST often rises more because muscle makes it. If your AST is mildly high, your clinician may ask you to repeat the test after a few days of rest.
Does a normal AST mean my liver is healthy?
Not always. AST and ALT can be normal even in people with chronic liver conditions, including fatty liver disease and hepatitis C. Doctors look at your risk factors and other tests too.
Is SGOT the same as AST?
Yes. SGOT (serum glutamic oxaloacetic transaminase) is the older name for AST. Some reports also use GOT, ASAT or TGO, and they all mean the same test.
Show the science and sources
Units
- 1 U/L = 1 U/L
- 1 U/L = 0.01667 µkat/L
Is a change real?
AST naturally varies about 9.5% from test to test in the same healthy person. Between two results from the same lab, a change of roughly 30% or more is unlikely to be day-to-day noise or lab variation (95% reference change value). Source: The European Biological Variation Study (EuBIVAS): a summary report.
For clinicians and researchers
AST (EC 2.6.1.1) transfers an amino group from aspartate to α-ketoglutarate and needs pyridoxal-5'-phosphate (vitamin B6) as a cofactor. Pyridoxal-5'-phosphate deficiency lowers ALT activity more than AST, which contributes to a higher AST:ALT ratio in alcohol-related liver disease. AST is present in liver, heart, skeletal muscle, kidney, brain and red cells. In liver about 20% is cytosolic and 80% mitochondrial, and it is concentrated in zone 3 of the acinus, so ischemic or toxic injury tends to raise AST more. Circulating half-life is about 17 hours for total AST and about 87 hours for mitochondrial AST. LOINC separates assays run with pyridoxal-5'-phosphate (30239-8, used by Mayo) from assays without it (88112-8). Mayo reports a photometric method and Labcorp a kinetic one. Elevations are often graded as mild (under 5 times the upper reference limit), moderate (5 to 10 times) or marked (over 10 times), though no uniform definition exists. In acute liver injury, levels above about 75 times the upper limit point to ischemic or toxic injury in more than 90% of cases. An AST:ALT ratio above 1 is linked to more advanced fibrosis in adults, even when both values are within range (BSG 2018). In alcohol-related liver disease the ratio exceeds 1 in most patients and exceeds 2 in about 70% (Cohen and Kaplan, as cited by Giannini 2005). Isolated AST rises should prompt a look at muscle, heart, hemolysis, celiac disease and macro-AST (AST bound into a large protein complex, with normal CK and ALT). Reference intervals are sex- and age-dependent and differ between labs and methods.
LOINC 1920-8 (primary), 30239-8, 88112-8, 112899-0. Specimen: serum-or-plasma.
Sources
- Comprehensive Metabolic Panel, Serum (test ID CMAMA), Mayo Clinic Laboratories
- Liver Profile, Serum (test ID LIVPR), Mayo Clinic Laboratories
- Aspartate Aminotransferase (AST/SGOT) (test 001123), Labcorp
- Pediatric Testing Reference Ranges, Labcorp (2022)
- Aspartate Aminotransferase, Serum or Plasma (test 0020007), ARUP Laboratories
- ABIM Laboratory Test Reference Ranges (January 2026), American Board of Internal Medicine (2026)
- Guidelines on the management of abnormal liver blood tests, Gut (British Society of Gastroenterology) (2018)
- Liver enzyme alteration: a guide for clinicians, Canadian Medical Association Journal (2005)
- AST Test, MedlinePlus, National Library of Medicine
AI-verified against cited sources. Awaiting expert review. Last reviewed 2026-10-03. How we build and check these pages.