Divide AST by ALT and read the classical pattern bands (≥2, 1–2, <1) with an honest “not informative” gate when both enzymes are normal.
100% client-side — your numbers never leave this browser.
Educational tool only — not medical advice.
The De Ritis ratio is pattern information from the medical literature, not a diagnosis of liver disease. It cannot confirm or rule out any condition. Always discuss liver test results with a qualified clinician.
Try a worked example (all recomputed by the engine):
Please enter positive numbers for AST, ALT and ULN (both enzymes must be > 0, ULN > 0).
Your De Ritis ratio
2.00
Strongly AST-dominant — ratio ≥ 2
ALT ÷ AST (reciprocal)
0.50
Ratio is unitless
U/L ÷ U/L
AST: 2.0× ULN
ALT: 1.0× ULN
Bar scale 0–10× ULN. Red tick marks your ULN (1×).
How it was computed
Pattern information, not a diagnosis.
This band describes what the medical literature classically associates with this ratio pattern. It does not diagnose alcoholic liver disease, cirrhosis, hepatitis or fatty liver — and it cannot rule any of them out.
When is the ratio worth reading — and when is it not?
At least one enzyme above your lab's ULN. The ratio is pattern information about elevated enzymes; two normal values give a meaningless number.
Both enzymes in the same units. U/L and IU/L are equivalent for enzyme activity; 1 µkat/L = 60 U/L. Mixed units silently corrupt the ratio.
Read alongside absolute levels. A ratio of 2 from 80/40 means something very different from 2.0 computed as 400/200 — the ×ULN bars above show this.
Not within days of hard exercise. Strenuous workouts raise AST for days while ALT barely moves — a classic false “≥ 2”.
Not with muscle injury, rhabdomyolysis, heart attack or a hemolyzed sample. AST lives in muscle, heart and red blood cells too.
Never as a diagnosis. It is one hint among history, full labs, imaging and validated scores.
De Ritis ratio vs fibrosis scores (know the boundary)
This tool computes only the standalone AST/ALT ratio — a pattern hint about the type of liver injury. It does not estimate fibrosis stage and uses no platelets or age. For validated fibrosis screening, use a proper score:
FIB-4 calculator — age, AST, ALT and platelets with published cutoffs (<1.30 / >2.67); the first-line non-invasive fibrosis screen.
APRI calculator — AST-to-platelet ratio index, another validated fibrosis hint.
The AST/ALT ratio, also called the De Ritis ratio after De Ritis, Coltorti & Giusti (1957), is the concentration of the enzyme aspartate aminotransferase (AST) divided by the concentration of alanine aminotransferase (ALT) in blood. Because both values use the same units, the ratio is a unitless number. It is computed from your lab results — it is not measured directly — and it is used as pattern information alongside the absolute enzyme levels, never as a standalone diagnosis.
How do I calculate my AST/ALT ratio?
Divide your AST value by your ALT value, with both in the same units (U/L is standard). Example: AST 80 U/L ÷ ALT 40 U/L = 2.00. If your lab reports different units for the two enzymes, convert both to U/L first — the calculator above does this automatically. The result is unitless, so the same ratio in µkat/L gives the identical number.
What is a normal AST/ALT ratio?
In healthy people both enzymes are within the normal range and the ratio is typically around 0.7–1.2, often near 0.8–1.0 — but there is no official “normal range” for the ratio itself, because a ratio of two normal values carries no clinical information. The reference you should compare against is each enzyme's own upper limit of normal (ULN) on your lab report, not the ratio.
What does an AST/ALT ratio above 2 mean?
A ratio of 2 or more with elevated enzymes is the classical pattern described in alcoholic liver injury. It means AST is at least twice ALT. Important caveats: it does not confirm alcohol-related disease — clinical history, GGT and further testing are required — and non-liver causes of high AST (strenuous exercise, rhabdomyolysis, muscle injury, hemolyzed blood sample) can produce the same pattern. Discuss any high result with a clinician.
What does an AST/ALT ratio below 1 mean?
A ratio below 1 means ALT is higher than AST — the most common pattern when the liver is injured, because ALT is more liver-specific and rises preferentially. Medical literature classically associates it with viral hepatitis, MASLD (metabolic dysfunction-associated steatotic liver disease, formerly NAFLD) and most acute hepatocellular injury. It is a pattern hint, not a diagnosis, and the absolute enzyme levels matter more than the ratio alone.
What does an AST/ALT ratio between 1 and 2 mean?
A ratio at or above 1 with elevated enzymes is the pattern classically described with advanced fibrosis or cirrhosis: as functional liver mass shrinks, AST clearance falls and ALT synthesis drops, so AST overtakes ALT. The same band can also appear transiently in other settings, so it is only interpretable in clinical context — for example alongside a fibrosis score such as FIB-4 — and never on its own.
Why is my AST higher than my ALT?
AST is not liver-specific: it is also abundant in skeletal muscle, heart muscle, red blood cells and kidneys, while ALT is concentrated mainly in the liver. So AST can exceed ALT for non-liver reasons — intense exercise or muscle injury, rhabdomyolysis, heart attack, hemolysis (a damaged blood sample), or certain drugs. If your AST is high but ALT is normal, a clinician will usually look for these causes before assuming liver disease.
Can exercise or muscle damage affect the AST/ALT ratio?
Yes — this is one of the biggest traps in reading the ratio. Strenuous exercise, especially unaccustomed or eccentric exercise, can raise AST for days while ALT barely moves, pushing the ratio above 2 without any liver problem. Rhabdomyolysis, muscle trauma and even intramuscular injections do the same. If you trained hard within a few days of the blood draw, tell your clinician; a CK (creatine kinase) test distinguishes muscle from liver origin.
What units do AST and ALT use, and does the unit change the ratio?
U/L (equivalent to IU/L for enzyme activity) is the standard reporting unit worldwide. Some labs report µkat/L: 1 µkat/L equals 60 U/L exactly, so multiply by 60 to convert. Because the ratio divides two values in the same units, the units cancel out — the ratio is identical whether you compute it in U/L or µkat/L, as long as both enzymes use the same unit.
When is the AST/ALT ratio NOT meaningful?
The ratio is not worth reading when both enzymes are within the normal range — a ratio of two normal numbers is noise, not information. It is also unreliable when AST is raised by non-liver causes (exercise, muscle injury, hemolysis), when only one enzyme is trivially above normal, or as a screening test in people without any liver risk. The calculator above flags this automatically: if neither enzyme exceeds your lab's upper limit of normal, it reports the ratio as not informative.
What is the difference between the De Ritis ratio and FIB-4?
They answer different questions. The De Ritis ratio (AST ÷ ALT) is a simple pattern hint about the type of liver injury. FIB-4 is a validated fibrosis risk score that combines age, AST, ALT and platelet count with published cutoffs (<1.30 low risk under 65, >2.67 high risk) to estimate the likelihood of advanced fibrosis. FIB-4 is the appropriate first-line non-invasive screening tool; the De Ritis ratio adds context but cannot stage fibrosis. Try our FIB-4 calculator for the screening score.
Can the AST/ALT ratio diagnose cirrhosis or alcoholic liver disease?
No. The ratio is an educational pattern hint, not a diagnostic test. A ratio above 2 is classically associated with alcoholic liver injury and a ratio above 1 with cirrhosis in the medical literature, but association is not diagnosis: sensitivity and specificity are modest, and many other conditions shift the ratio. Diagnosis of liver disease requires clinical history, physical examination, full lab panels, imaging and sometimes biopsy — a single ratio can never substitute for that.
What upper limit of normal (ULN) should I use?
Always use the ULN printed on your own lab report first, because reference ranges vary by laboratory, assay and population. As a rough guide, many labs use 40 U/L for both enzymes, while the AASLD-endorsed healthy thresholds (Pratt & Kaplan) are 29–33 U/L for men and 19–25 U/L for women. The calculator offers 40, 33 and 25 as presets plus a custom field so you can match your lab exactly.
Is this calculator medical advice?
No. This is an educational tool that computes the AST/ALT ratio and explains the classical pattern interpretations from the medical literature. It does not diagnose liver disease, does not rule anything out, and is not a substitute for professional medical advice, diagnosis or treatment. All of your entries stay in your browser and are never sent anywhere. Always discuss liver test results with a qualified clinician.
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