π©Έ AST/ALT Ratio Calculator
The De Ritis ratio: which enzyme dominates.
AST/ALT ratio
For informational purposes only, not medical advice. Consult a healthcare professional.
AST and ALT are the two liver enzymes on every metabolic panel, and their ratio is often more informative than either alone. ALT lives mostly in the liver; AST lives in liver, heart, and muscle. When the ratio of AST to ALT climbs above 2, alcoholic liver disease tops the differential. When ALT dominates, viral hepatitis and fatty liver lead.
Known as the De Ritis ratio after the physician who described it, this simple division helps sort the cause of liver injury before expensive testing. This calculator computes it and explains the patterns.
How to use this calculator
Take AST and ALT from the same blood draw, in IU/L.
Enter AST in IU/L.
Enter ALT in IU/L.
Read the ratio and the likely pattern, then interpret it with the absolute levels.
The ratio and its patterns
Divide AST by ALT. The classic teaching patterns:
Alcohol raises AST disproportionately because it depletes vitamin B6 (needed more by ALT) and injures mitochondria (where much AST lives). In alcoholic hepatitis, AST is typically under 300 even when the ratio exceeds 2; an AST over 500 with a high ratio points elsewhere.
Worked example
AST 120, ALT 60. The ratio is 120/60 = 2.0. With a history of heavy drinking and AST well under 300, this fits alcoholic liver disease, and the next steps are alcohol counseling and abstinence support, not more labs.
Contrast AST 850, ALT 1200: ratio 0.71, ALT-dominant. This is acute hepatocellular injury: viral hepatitis, ischemic injury ("shock liver"), or drug toxicity. The absolute numbers scream acuity while the ratio whispers the category.
What your result means
Above 2.0: think alcohol first, then cirrhosis from any cause (fibrosis inverts the ratio over time as ALT production fades). 1.0 to 2.0: the gray zone: cirrhosis, resolving acute injury, or muscle injury raising AST. Below 1.0: ALT-dominant injury: viral hepatitis, NAFLD, hemochromatosis early on.
Muscle injury is the great mimicker: strenuous exercise, statins, or muscle disease raise AST without liver involvement, and the ratio misleads. Check CK when the story involves muscles. For related liver screens, see our APRI fibrosis calculator and A/G ratio calculator.
Beyond the ratio
The ratio is a clue, not a verdict. Alcoholic liver disease needs a drinking history, not just math. Viral hepatitis needs serologies. NAFLD needs imaging and metabolic context. And the trend across months often matters more than one ratio: a ratio climbing from 0.8 to 1.6 over two years suggests developing fibrosis regardless of the cause.
When enzymes are normal, the ratio is noise: dividing two normal numbers produces patterns without meaning. Only interpret the ratio when at least one enzyme is elevated.
GGT and ALP: the cholestatic partners
AST and ALT describe hepatocellular injury; GGT and alkaline phosphatase describe cholestasis (blocked bile flow). When ALP and GGT rise disproportionately, the problem is bile ducts or gallstones rather than liver cells: think obstruction, not hepatitis. The pattern of which enzymes rise sorts liver injury into hepatocellular, cholestatic, or mixed.
GGT also corroborates alcohol use: it rises with chronic heavy drinking and falls with abstinence, making it a useful trend marker alongside the AST/ALT ratio. An isolated high GGT with normal everything else is often enzyme induction from alcohol or medications rather than liver damage.
NAFLD: the modern driver of abnormal LFTs
Non-alcoholic fatty liver disease is now the most common cause of mildly elevated liver enzymes in the US, tracking the obesity epidemic. The typical pattern is ALT-dominant with a ratio below 1, mild elevations (under 100), and metabolic risk factors: obesity, diabetes, high triglycerides.
The good news: early NAFLD responds to weight loss, with 7 to 10 percent body-weight reduction improving liver fat and inflammation measurably. The AST/ALT ratio creeping upward over years in a NAFLD patient suggests developing fibrosis and deserves staging with FIB-4 or elastography.
Drug-induced liver injury: the medication check
Before blaming the liver, blame the medicine cabinet. Hundreds of drugs injure the liver, and the pattern helps: acetaminophen overdose gives massive ALT-dominant injury; isoniazid and many antibiotics give hepatocellular patterns; anabolic steroids and some contraceptives give cholestatic patterns with high ALP.
Supplements deserve equal suspicion: green tea extract, kava, and various bodybuilding products have documented liver injury cases, and patients often do not mention them because "natural" feels safe. Herbal does not mean harmless to the liver.
The diagnostic test for drug injury is stopping the drug: enzymes should fall within days to weeks. A careful medication and supplement timeline, going back 3 months, belongs in every unexplained enzyme elevation workup, and the AST/ALT ratio is read only after that review.
When to recheck liver enzymes
Mildly elevated enzymes without symptoms are usually rechecked in 3 to 6 months, with alcohol abstinence and medication review in between. Many normalize on their own. Rising trends, new symptoms, or enzymes over 3 times normal accelerate the workup to imaging and serologies without waiting.
For informational purposes only, not medical advice. Consult a healthcare professional.
Frequently Asked Questions
What is a normal AST/ALT ratio?
Around 0.8 to 1.0 in healthy people. The ratio becomes meaningful when enzymes are elevated: above 2 suggests alcohol-related disease, below 1 suggests viral or fatty liver patterns.
What does an AST/ALT ratio over 2 mean?
Most commonly alcoholic liver disease, particularly with AST under 300 and heavy alcohol use. Advanced cirrhosis from any cause can also push the ratio above 2.
Can exercise raise AST?
Yes. AST lives in muscle, so intense exercise, muscle injury, and statin-related muscle effects raise AST without liver disease. Check creatine kinase if muscles are the suspect.
What causes very high ALT over 1000?
Acute viral hepatitis, ischemic hepatitis (shock liver), acetaminophen toxicity, or other drug/toxin injury. These are emergencies until evaluated.
Is the AST/ALT ratio enough to diagnose liver disease?
No. It sorts likely causes but diagnosis needs history, imaging, and often serologies or biopsy. The ratio is a starting clue.
Why does cirrhosis raise the ratio?
As fibrosis advances, ALT production falls faster than AST, and reduced clearance raises AST. The ratio creeps above 1 and often above 2 in established cirrhosis.
What is the De Ritis ratio?
Another name for the AST/ALT ratio, after Fernando De Ritis who described its use in viral hepatitis in 1957.
Should I worry about a slightly high ratio with normal enzymes?
No. With both enzymes normal, the ratio is mathematically noisy and clinically meaningless. It only matters when enzymes are elevated.