What is AST / ALT Ratio?
AST and ALT are two enzymes that convert amino acids, and they come from the same tube of blood. The difference lies in where they sit. ALT sits almost only in the liver cells; AST also sits in muscles, heart and red blood cells, and in the liver cell it sits deeper, in the mitochondria, where alcohol releases it. So the ratio between the two tells something the single values do not: where the damage sits and what it looks like. In fatty liver, the most common liver condition, mainly ALT leaks and the ratio sits below 1. With alcohol mainly AST leaks, and alcohol also depletes the vitamin B6 with which ALT is measured, so the ratio rises, above 2 in the classic case. With muscle damage after hard training AST rises without the liver joining in, and the ratio is high while ALT is normal. And when a liver scars through years of strain, the ratio creeps upward, because the damaged cells release more AST. A ratio that shifts over the years from below 1 to above 1 is thereby an early sign that the liver is no longer just fatty. Your report shows the ratio as a bare number, without a unit. Healthy runs up to 1.3 in men and up to 1.7 in women, and most healthy people sit around 0.8 to 0.9. No test is needed for it: you divide your AST by your ALT, both in U/L.
Why is AST / ALT Ratio relevant?
The ratio is the value that with a raised ALT or AST answers the question you are really asking: is this fat, alcohol or muscles. Fatty liver gives an ALT higher than AST, with belly fat, high triglycerides and a low HDL alongside; that is the ratio below 1, and the treatment is weight loss and less sugar. Alcohol gives an AST that rises more than ALT, with a high gamma-GT and often a high MCV; that is the ratio above 2, and the treatment is cutting down. Muscles give a high AST with a normal ALT, after training, and that is not worth a treatment. The same single values, three different answers, and the division tells them apart. The second reason is time. Anyone who has a slightly raised ALT for years from fatty liver keeps, in the favourable case, a ratio below 1. If that ratio creeps up over the years to 1 and above, that is a sign the liver is starting to form scars, and that is the moment the FIB-4 score belongs with it. A ratio you follow over the years thereby says more than one result. And the third reason is what the ratio does not do. It was devised for the situation in which AST or ALT are already raised. If both sit within the range, the division yields a number that is about nothing: two normal values divided by each other say nothing about your liver.
AST / ALT Ratio decision limits
What counts beside the number:
- Whether AST or ALT themselves fall outside the range, because otherwise the division says nothing
- Gamma-GT, which goes up with alcohol and liver and stays normal with muscles
- CK, which shows muscle damage directly
- Belly fat, triglycerides and HDL, the company of fatty liver
- How much you drink, and when you last trained hard
- The trend over the years, because a rising ratio is a liver that is changing
These are decision limits and not normal values: no lab prints a band for the ratio, and the limits above come from the review that describes the ratio. They apply only when AST or ALT themselves fall outside the range; two normal values divided by each other say nothing. Muscle damage after training lifts the ratio for a few days without the liver being involved.
AST / ALT = AST divided by ALT, both in U/L
Dividing is dividing: AST divided by ALT, both in U/L and from the same draw. No lab prints a band for the result; the limits in the table are decision limits from the review, and they apply only when AST or ALT themselves are raised.
÷ =
AST / ALT Ratio high or low: what it means
Look first at whether AST or ALT falls outside your own lab's range. If not, leave the ratio alone; it says nothing then. A low ratio, below 1, with a raised ALT means ALT dominates. From common to rare: fatty liver with excess weight, a viral hepatitis that is recovering, and alcohol-related liver disease at an early stage, because there too a share sits below 1. Belly fat, triglycerides and gamma-GT say which. A high ratio, above 1 and certainly above 2, means AST dominates. In order: muscle damage after hard exertion, with a normal ALT and a high CK; alcoholic hepatitis, with a high gamma-GT; scarring in a chronic liver disease, in which the ratio rises over the years; and rarely a fulminant viral hepatitis. AST disappears from the blood faster than ALT, so a ratio that is high after muscle damage falls back within days. What you do about it: with a ratio below 1 with fatty liver, weight loss, less sugar and exercise are the levers. With a ratio above 2 with a high gamma-GT it is cutting down on alcohol, and the ratio falls in the weeks after. With a ratio that rises over the years, the FIB-4 belongs with it. Set the ratio beside AST and ALT themselves, gamma-GT, bilirubin and ALP, and in an athlete beside CK. Have blood drawn on a rest day, because muscle damage lifts the ratio for a few days.
What lowers it
ALT dominates: the liver cell itself leaks, without alcohol and without muscles.
| Cause | How often |
|---|---|
| An acute viral hepatitis that is recoveringALT stays raised longer than AST, because it disappears from the blood more slowly; the ratio falls below 1 while the liver recovers | Often |
| Fatty liver and excess weightThe most common reason in anyone otherwise healthy; ALT leaks more than AST, and belly fat, high triglycerides and a low HDL belong with it | Often |
| Alcohol-related liver diseaseAt an early stage a share of people with alcohol damage also sit below 1; gamma-GT and MCV then say more than the ratio | Sometimes |
What raises it
AST dominates: muscles, alcohol, or a liver forming scars.
| Cause | How often |
|---|---|
| Acute muscle damage and hard exertionMuscles contain plenty of AST and little ALT; after hard training the ratio is high with a normal ALT and a high CK, and falls within days | Often |
| Alcoholic hepatitisAlcohol mainly frees AST and hampers the measurement of ALT; above 2 with a high gamma-GT is the classic picture, though a share of people with alcohol damage sit lower | Often |
| Fibrosis or cirrhosis in chronic liver diseaseA liver forming scars releases more AST; a ratio creeping over the years from below 1 to above it is the early sign, and then the FIB-4 belongs with it | Sometimes |
| A fulminant course of acute viral hepatitisIn a severe hepatitis so many cells break down that the deeper AST is released too; rare, and then with a sharply raised bilirubin | Rare |
How does an AST / ALT Ratio blood test work?
- Referral
- Not needed. The ratio is a division of AST by ALT, which are both in the liver panel you can have measured yourself.
- When
- On a rest day, at least two days after hard exertion, because muscle damage lifts AST and with it the ratio for a few days.
- Which test
- AST / ALT Ratio is in the comprehensive test (€229) and in .
- Where to draw
- You can draw at 250+ locations near you, no referral needed. See the locations
Frequently asked questions
What is the AST/ALT ratio?
Your AST divided by your ALT, both from the same draw. It is a calculation, not a test. The ratio says something because the two enzymes do not sit in the same place: ALT almost only in the liver, AST also in muscles and heart, and deeper in the liver cell, where alcohol releases it. Which of the two dominates therefore says where a rise comes from.
Is there a normal value for the ratio?
No band as with an ordinary test, because no lab measures the ratio. There are limits, though: healthy runs up to 1.3 in men and up to 1.7 in women, and most healthy people sit around 0.8 to 0.9. Those limits apply only when AST or ALT themselves are raised; if both sit within the range, the division says nothing.
What does a ratio below 1 mean?
That ALT dominates, and with a raised ALT that is usually fatty liver: fat in the liver from belly fat, sugar and too little exercise, with high triglycerides and a low HDL alongside. A viral hepatitis that is recovering also sits below 1, and a share of people with alcohol damage at an early stage. Most healthy people sit there too, so below 1 is not a suspicious result.
What does a ratio above 2 mean?
That AST dominates. In a liver problem that is the classic picture of alcohol, with a high gamma-GT and often a high MCV alongside, though a share of people with alcohol damage sit lower. With a normal ALT and a high CK it is muscle damage after hard training, and then the ratio falls within days. And in a liver that has been under strain for years, a rising ratio points at scarring.
How does the ratio separate alcohol from fatty liver?
Alcohol mainly frees AST, which sits deeper in the liver cell, and it depletes the vitamin B6 with which ALT is measured; so AST rises more than ALT. Fatty liver mainly lets ALT leak. The same single values thus give two different ratios: below 1 is fat, above 2 is alcohol, and gamma-GT confirms it. The difference counts, because one asks for weight loss and the other for cutting down.
Why does the ratio say nothing when AST and ALT are normal?
Because it was devised for the situation in which one of the two is raised. Dividing two values within the range by each other yields a number that is about nothing: someone with an AST of 20 and an ALT of 15 has a ratio above 1 and a healthy liver. So look first at whether AST or ALT themselves fall outside the range, and otherwise leave the division alone.
What does a ratio that rises over the years mean?
That the liver is changing. Anyone who has a slightly raised ALT for years from fatty liver keeps, in the favourable case, a ratio below 1. If it creeps up to 1 and above, the damaged cells release more AST, and that is the early sign of scarring. That is the moment the FIB-4 score belongs with it, which estimates how much scarring the liver has.
Can I calculate the ratio myself?
Yes: AST divided by ALT, both in U/L and from the same draw. Have blood drawn on a rest day, because muscle damage after hard training lifts AST and with it the ratio for a few days. And read the result beside gamma-GT, bilirubin and ALP, because those say what the ratio alone cannot.
Which tests include AST / ALT Ratio?
AST / ALT Ratio is in the Liver function test (€59, also as an add-on for €15), in the comprehensive test (€229) and in .
Related biomarkers
Sources
- 1.Botros M, Sikaris KA, The de Ritis Ratio: The Test of Time, The Clinical Biochemist Reviews. 2013. pmc.ncbi.nlm.nih.gov
- 2.Mera JR et al., Influence of gender on the ratio of serum aspartate aminotransferase (AST) to alanine aminotransferase (ALT) in patients with and without hyperbilirubinemia, Digestive Diseases and Sciences. 2008. pubmed.ncbi.nlm.nih.gov
- 3.De Ritis F, Coltorti M, Giusti G, An enzymic test for the diagnosis of viral hepatitis: the transaminase serum activities, Clinica Chimica Acta. 1957. pubmed.ncbi.nlm.nih.gov
- 4.Unilabs, test catalogue (Dutch): the full index. 2026. bepalingenklapper.nl
- 5.Unilabs, test catalogue (Dutch): AST. 2026. bepalingenklapper.nl
- 6.Unilabs, test catalogue (Dutch): ALT. 2026. bepalingenklapper.nl
- 7.Star-shl, test catalogue (Dutch): the full overview. 2026. star-shl.nl
- 8.Certe, test catalogue (Dutch): AST. 2026. bepalingenwijzer.certe.nl
- 9.Clinical Diagnostics, lab guide (Dutch): AST. 2026. clinicaldiagnostics.nl
- 10.LESA Laboratory diagnostics (Dutch primary-care laboratory agreement). 2026. richtlijnen.nhg.org
Educational information only, not medical advice. Consult a healthcare professional for clinical decisions.
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