Liver enzyme check
AST/ALT ratio calculator
AST and ALT are the two liver enzymes on a standard blood panel. Comparing them gives a ratio that doctors use as one clue among many. Here is how to work it out and what the US gastroenterology guideline says about it.
Your lab values
AST and ALT are on a liver panel or comprehensive metabolic panel, in U/L (also written IU/L). Nothing you enter leaves this page.
What you will see
Your AST/ALT ratio, what the ACG guideline says about that range, and how your ALT compares with its healthy upper limit.
Educational only, not medical advice. A ratio is a clue, not a diagnosis.
Source
ACG Clinical Guideline: Evaluation of Abnormal Liver Chemistries (Kwo PY, Cohen SM, Lim JK; Am J Gastroenterol 2017), from the American College of Gastroenterology.
Validated in
Adults with AST and ALT results from a standard blood test.
Limits
The ratio is a pattern, not a test for any one disease. AST also comes from muscle and the heart, so hard exercise, a muscle injury or a heart problem can raise it. It does not measure liver scarring; FIB-4 is built for that.
What AST and ALT are
Both are enzymes released when cells are damaged. ALT is found mainly in the liver, so it points more specifically to liver damage (MedlinePlus). AST is found mainly in the liver too, but also in the heart, muscles and other tissues (MedlinePlus). High levels of either may mean some type of liver damage (MedlinePlus).
What the ACG guideline says about the ratio
The American College of Gastroenterology's guideline on abnormal liver tests describes these patterns (ACG 2017):
| AST/ALT ratio | What the guideline says |
|---|---|
| Under 2:1 | No specific pattern is described. This does not rule out liver disease. |
| 2:1 or higher | A pattern commonly associated with alcohol-related liver injury, with AST and ALT rarely above 300 U/L |
| Over 3:1 | Further increases the likelihood of alcohol-related liver disease |
The guideline explains that the high ratio largely reflects lower ALT activity, linked to a shortage of vitamin B6 (pyridoxine) in people with alcohol-related liver disease (ACG 2017). It also says alcohol use should be asked about in everyone with abnormal liver tests (ACG 2017).
A ratio is one clue. The guideline's evaluation also looks at how high the enzymes are, the history, a physical exam and other blood tests and imaging (ACG 2017).
What counts as a high ALT
Lab reference ranges vary, and many are set higher than a truly healthy level. The ACG guideline gives a healthy normal ALT of 29 to 33 U/L for men and 19 to 25 U/L for women, and says levels above that should be assessed (ACG 2017). This calculator uses 33 and 25 as the upper limits. Your lab report may use a higher number, so it can mark a result normal that is above these.
The guideline also grades how high AST and ALT are, as multiples of the upper limit of normal (ULN) (ACG 2017):
| Grade | AST and ALT level |
|---|---|
| Borderline | Under 2 times the ULN |
| Mild | 2 to 5 times the ULN |
| Moderate | 5 to 15 times the ULN |
| Severe | Over 15 times the ULN |
| Massive | Over 10,000 U/L |
AST/ALT ratio and liver scarring
AST and ALT also go into FIB-4, a score that estimates the chance of advanced liver scarring using age and platelet count as well. If you have those numbers, the FIB-4 calculator answers a different question from this ratio. For fatty liver, see fatty liver disease (MASLD), explained.
Common questions
Is an AST/ALT ratio over 2 always caused by alcohol?
No. The guideline calls it a pattern commonly associated with alcohol-related liver injury (ACG 2017), not proof. AST also rises with muscle and heart problems (MedlinePlus), which can push the ratio up.
What if my AST and ALT are both normal?
Then the ratio tells you little on its own. The guideline's patterns are described for abnormal liver tests (ACG 2017). Ask your doctor if anything else on your report concerns you.
What should I do with a high ratio?
Talk to your doctor about the full result. This page does not give treatment advice. If you want to look at your drinking, our AUDIT-C alcohol check takes three questions.
Sources
- Kwo PY, Cohen SM, Lim JK. ACG Clinical Guideline: Evaluation of Abnormal Liver Chemistries. Am J Gastroenterol. 2017;112(1):18-35. doi.org/10.1038/ajg.2016.517
- MedlinePlus (US National Library of Medicine). AST Test. medlineplus.gov/lab-tests/ast-test/
- MedlinePlus (US National Library of Medicine). ALT Blood Test. medlineplus.gov/lab-tests/alt-blood-test/
Written and maintained by the uncovermyrisk.com editorial team. We do not have a medical reviewer; every claim links to its primary source above. Last reviewed: 2026-10-27. Spotted an error? See About.