Calculate the AST to ALT ratio (De Ritis ratio) and R factor to review common liver-injury patterns alongside the rest of the liver panel.
The AST:ALT Ratio Calculator (De Ritis Ratio) analyzes the relationship between your liver enzymes to help organize abnormal liver tests into a review-friendly pattern. First described by Fernando De Ritis in 1957, this ratio remains a simple bedside clue for interpreting transaminase changes.
The ratio of AST to ALT provides critical diagnostic information because these enzymes are distributed differently in the liver and have different half-lives. ALT is more liver-specific and predominates in hepatocellular injury, while AST is also found in muscle, heart, kidney, and red blood cells. An AST:ALT ratio above 2 with AST under 300 is one of the most reliable non-invasive markers for alcoholic liver disease. As liver fibrosis progresses to cirrhosis, the ratio typically rises above 1 regardless of etiology, reflecting decreased ALT synthesis by the failing liver.
This calculator also computes the R factor (ratio of ALT elevation to ALP elevation), which helps frame hepatocellular versus cholestatic patterns during the initial review of abnormal liver tests. Together with GGT and the broader clinical picture, these ratios help organize the differential before imaging, serologies, or specialist follow-up.
The AST:ALT ratio is a quick way to frame an abnormal liver panel. It helps separate patterns that are more consistent with alcohol-related injury, viral or metabolic hepatitis, cholestasis, or a non-hepatic source of AST so the next test is chosen with more context.
De Ritis Ratio = AST / ALT R Factor = (ALT / ALT ULN) / (ALP / ALP ULN) R >5 → Hepatocellular pattern R 2-5 → Mixed pattern R <2 → Cholestatic pattern De Ritis <1 → Viral/metabolic hepatitis De Ritis 1-2 → Fibrosis/cirrhosis progression De Ritis >2 → Alcoholic liver disease De Ritis >3 → Highly suggestive alcoholic etiology
Result: AST:ALT = 0.80 (Normal pattern). R Factor = 3.5 (Hepatocellular). ALT = 2.5× ULN (Mild elevation).
An AST:ALT ratio of 0.80 (less than 1) is typical of viral hepatitis, MASLD, or drug-induced liver injury. The R factor of 3.5 confirms a hepatocellular injury pattern. Normal GGT makes alcohol unlikely.
Fernando De Ritis first described the AST:ALT ratio in 1957 while studying viral hepatitis. Since then, it has become one of the most widely used liver enzyme ratios in clinical medicine. Its enduring value lies in its simplicity: no special tests, no calculations beyond simple division, and applicability across all liver disease etiologies.
The R factor was formalized by the Council for International Organizations of Medical Sciences (CIOMS) for classifying drug-induced liver injury (DILI). It separates liver injury into hepatocellular, cholestatic, and mixed patterns. This helps organize the next step in evaluation, but the page should be read as a liver-panel interpretation aid rather than a stand-alone diagnostic algorithm.
Beyond etiology, the De Ritis ratio has been integrated into composite fibrosis scores. A ratio consistently above 1 in chronic hepatitis C is an independent predictor of advanced fibrosis. The ratio is incorporated into the AAR (AST-ALT ratio) score and contributes to other non-invasive fibrosis assessments alongside platelet count and albumin.
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This page calculates the De Ritis ratio as "AST / ALT" and the R factor as "(ALT / ALT ULN) / (ALP / ALP ULN)", then groups the results into the usual bedside pattern ranges for hepatocellular, cholestatic, mixed, and alcohol-associated liver-injury review. It keeps the ratio tables visible so the numbers can be read in the context of the broader liver panel rather than as a stand-alone diagnosis.
The output is meant to support initial liver-test interpretation, not to establish etiology by itself. Alcohol use, muscle injury, hemolysis, cirrhosis, cholestatic disease, and many other clinical factors can change the pattern, so the ratio should be read alongside bilirubin, INR, albumin, imaging, exposure history, and the rest of the workup.
A ratio above 2, especially when AST remains under about 300 U/L, is classically associated with alcohol-related liver injury, but it is not diagnostic by itself. Muscle injury, advanced fibrosis, hemolysis, and other conditions can also push AST above ALT.
Yes. In viral hepatitis and MASLD, the ratio is typically below 1 early on (ALT > AST). As fibrosis advances to cirrhosis, the ratio rises above 1 because the cirrhotic liver produces less ALT. A rising ratio over time may indicate disease progression.
The R factor (also called R value) classifies liver injury as hepatocellular (R >5), cholestatic (R <2), or mixed (R 2-5). It is calculated as (ALT/ULN) ÷ (ALP/ULN) and is the first step in the DILI (drug-induced liver injury) assessment algorithm.
Yes. AST is also found in skeletal muscle, heart, and red blood cells. Rhabdomyolysis, myocardial infarction, and hemolysis can dramatically elevate AST relative to ALT. Always check CK to rule out muscle injury if AST is disproportionately high.
GGT (gamma-glutamyl transferase) is elevated in biliary disease and alcohol use. An elevated GGT combined with AST:ALT >2 strongly suggests alcoholic liver disease. Elevated GGT with elevated ALP suggests biliary obstruction. Isolated GGT elevation has many causes (medications, obesity, enzyme induction).
Massive elevations (ALT >1000) are typically caused by acute viral hepatitis, ischemic hepatitis (shock liver), drug/toxin injury (acetaminophen), or acute biliary obstruction. Alcoholic hepatitis alone rarely causes AST above 300.