AST
Aspartate Aminotransferase
What this test measures
AST is an enzyme found in your liver, heart, and muscles. When these tissues are damaged, AST leaks into your blood. This test helps check liver health, though it is less specific to the liver than ALT.
Understanding the numbers
Typical range: 10-40 U/L
Ranges can vary between laboratories. AST can also be raised by heart or muscle problems, not just liver issues.
- Normal: 0–40 U/L
- Mildly raised: 40–100 U/L
- Moderately raised: 100–300 U/L
- Markedly raised: 300–500 U/L
Key numbers
- 40 U/L — Upper limit of normal
- 100 U/L — Moderate — investigate cause
Typical UK range. AST is less liver-specific than ALT — it is also found in heart, skeletal muscle and red cells. The AST:ALT ratio is a clinical clue: AST higher than ALT suggests alcohol or cirrhosis; ALT higher than AST is typical of fatty liver and viral hepatitis.
Ranges can vary slightly between laboratories — your report may show slightly different numbers. This page does not read or interpret your result; your GP looks at it alongside your history and other tests.
What a higher-than-normal result can mean
- Your liver cells may be damaged or inflamed
- Can also be raised by heart problems or muscle injury
- Heavy exercise can temporarily raise AST
- Your GP may want to do more tests to find the cause
Questions you could ask your GP
- Is my raised AST coming from my liver, heart, or muscles?
- Do I need other liver tests to get the full picture?
- Could any of my medicines or activities be affecting this?
- Should I have an ultrasound scan of my liver?
Example stories
These are made-up examples to show how results are talked about in real appointments. They are not real patients.
AST > ALT pattern — alcohol
Wasim's AST was 110, ALT 72, GGT 260, MCV 104. He drank around 40 units a week.
What the GP said: “The pattern of AST higher than ALT, plus a raised GGT and high MCV, points to alcohol-related liver injury. Cutting alcohol is the single most effective thing you can do — and the liver bounces back in early stages.”
What happened next: Wasim engaged with the alcohol service and stopped drinking. At three months all his liver tests were normal.
In alcohol-related liver disease, AST is typically higher than ALT (the classic AST:ALT ratio >1.5:1). Combined with raised GGT and high MCV, it's a clear pattern.
Raised AST after heart attack
Ravi was admitted with a heart attack. His AST was 180 U/L peaking 24 hours after admission, ALT 55, troponin markedly raised.
What the GP said: “The AST has risen from your heart muscle injury, not your liver. This is expected in a heart attack and will come down over a few days.”
What happened next: Ravi's AST normalised over a week after his PCI; his liver was not involved.
AST is released by heart and muscle too, not just liver. A raised AST with normal ALT and a clear non-liver clinical picture is often heart or muscle related — the liver tests don't need separate investigation.
Marathon runner — muscle AST
Juliet had bloods done three days after running her first marathon. AST 145, ALT 38, creatine kinase very raised.
What the GP said: “Exercise — especially extreme exercise like a marathon — releases AST from muscle. This will settle within a week. I don't think we need to investigate your liver based on this one number.”
What happened next: Her bloods were normal two weeks later.
Intense or prolonged exercise can raise AST (and CK). Ideally, liver tests are done away from heavy exercise, and a single AST rise after exertion doesn't need further investigation.
Cirrhosis — chronic raised AST
Charles had known cirrhosis from previous alcohol use. AST 78, ALT 45, platelets 112, albumin 32, INR 1.3.
What the GP said: “Your AST remains mildly raised because of your cirrhosis. What matters more are the signs the liver is stiff — low platelets, low albumin, raised INR. We keep you on the surveillance pathway for liver cancer.”
What happened next: Charles stayed off alcohol and had six-monthly surveillance. His other markers remained stable.
In chronic liver disease, the pattern of other tests (platelets, albumin, INR) tells you more about liver function than AST itself. Persistently raised AST in cirrhosis is the backdrop; the focus shifts to preventing complications.
Before you act on anything here
This page is general information, written to help you understand — it is not personal medical advice and it cannot tell you what is right for you. Talk to your own GP, pharmacist or nurse about your own health.
- Need help now but it's not an emergency? Call NHS 111 or use 111.nhs.uk.
- Emergency? Call 999 or go to A&E.