ALT vs AST: What the Ratio Between Them Tells You
Bottom line: ALT is the more liver-specific of the two. AST also comes from muscle, heart and red blood cells. Dividing AST by ALT gives the De Ritis ratio, and the pattern points in different directions: below 1 is the common pattern, above 2 points strongly at alcohol. The ratio only means anything if at least one enzyme is actually raised.
What each enzyme is, and where it comes from
Both are enzymes that sit inside cells and leak into the blood when those cells are stressed or damaged. The useful difference is which cells.
ALT (alanine aminotransferase) is concentrated in the liver. It is the more liver-specific of the pair, so a raised ALT points fairly directly at the liver.
AST (aspartate aminotransferase) is in the liver too, but also in skeletal muscle, heart muscle and red blood cells. A raised AST on its own is therefore less specific, and can have nothing to do with your liver at all.
Side by side
| ALT | AST | |
|---|---|---|
| Full name | Alanine aminotransferase | Aspartate aminotransferase |
| Main source | Liver | Liver, skeletal muscle, heart, red cells |
| Liver-specific? | Largely yes | No |
| Raised after hard exercise? | Sometimes | Often, and more so |
| What a rise usually reflects | Liver cell injury or fat in the liver | Liver, or muscle, or red cell breakdown |
Look up your own values: ALT, AST, bilirubin, ALP.
The De Ritis ratio, and how to read yours
Divide AST by ALT. That is the De Ritis ratio, first described by Fernando De Ritis in 1957 and still used because the pattern carries information the individual numbers do not.
| AST / ALT | Pattern | Commonly associated with |
|---|---|---|
| Below 1 | ALT-dominant | The most common pattern. Non-alcoholic fatty liver disease, viral hepatitis, acute liver injury. Also the usual pattern in healthy people. |
| 1 to 2 | Balanced to AST-leaning | Can reflect more advanced fibrosis, cirrhosis, or NASH. In someone with known fatty liver, a ratio crossing above 1 is watched as a possible sign of progression. |
| Above 2 | Strongly AST-dominant | Points strongly at alcohol-related liver disease. Also seen in muscle injury and in advanced cirrhosis. |
The ratio rises above 1 in about 92% of alcohol-related liver disease, and above 2 in about 70% of cases. That is why a ratio above 2 gets attention. It is a strong signal, not a diagnosis, and plenty of other things push AST up.
The mistake almost everyone makes with the ratio
The De Ritis ratio is only interpretable when at least one of the two enzymes is actually raised. If your ALT and AST are both comfortably in range, the ratio between them is arithmetic, not information. Dividing 18 by 25 tells you nothing about your liver.
This is the single most common misreading of these two numbers, and it generates a great deal of unnecessary worry. Read the absolute values first. Only if one is raised does the ratio start to mean something, and even then it belongs alongside GGT, bilirubin, ALP and how you actually feel.
When it is not your liver at all
Because AST lives in muscle as well, a few ordinary things can raise it:
- Hard exercise in the days before the draw. Resistance training and long endurance efforts both do it. This is common and benign.
- Muscle injury, including a recent fall or an intramuscular injection.
- Haemolysis, red cells breaking down, sometimes from the blood draw itself.
If your AST is up, your ALT is normal and you trained hard that week, that is worth mentioning before anyone reaches for a liver workup.
What actually happens next
For a mild, isolated rise, repeating the test after a few weeks is the usual first step, because a good proportion of mild elevations simply resolve. Before a repeat it is normal to be asked about alcohol, new medicines and supplements, and recent exercise, since all three move these numbers.
What this page cannot do is tell you what your result means for you. Two people with an identical ALT can need completely different things. That is a conversation with a clinician, and if your results came with a note asking you to make an appointment, make the appointment.
Frequently Asked Questions
What is a normal AST to ALT ratio?
In healthy people the ratio is usually below 1, meaning ALT sits a little higher than AST. A ratio of around 0.7 to 1.0 is typical and expected. The ratio only carries information when at least one of the two enzymes is actually raised.
What does an AST/ALT ratio above 2 mean?
It points strongly toward alcohol-related liver disease: the ratio exceeds 1 in about 92% of cases and 2 in about 70%. It is a strong signal rather than a diagnosis, and muscle injury and advanced cirrhosis can also produce it. It needs a clinician's interpretation alongside GGT and the absolute enzyme levels.
Which is more important, ALT or AST?
For the liver specifically, ALT. It is concentrated in liver tissue, whereas AST is also found in muscle, heart and red blood cells, so a raised AST is less specific. Read them together rather than picking one.
Can exercise raise ALT and AST?
Yes, and AST more than ALT, because AST is present in skeletal muscle. Hard resistance training or a long endurance session in the days before a blood draw can lift both. Worth mentioning to whoever ordered the test.
Should I worry about a mildly raised ALT?
Mild isolated elevations are common and a good proportion resolve on their own, which is why repeating the test after a few weeks is the usual first step rather than immediate investigation. That said, this page cannot tell you what your own result means, and if you were asked to book an appointment, book it.
BloodMarker does not provide medical advice, diagnose conditions, or recommend treatments. Reference ranges used across this site are published in full at doi.org/10.5281/zenodo.21694169. Talk to a clinician about your own results.