Normal liver enzyme levels generally fall below 40 units per liter (U/L) for most adults, though the exact cutoff depends on which enzyme is being measured, your sex, and the lab running the test. If you’ve just gotten blood work back and want to know whether your numbers look right, here’s what each value means and when an elevation actually matters.
The Main Enzymes on a Liver Panel
A standard liver panel measures several different proteins and enzymes. Each one reflects a slightly different aspect of liver health, so doctors look at the pattern across all of them rather than any single number in isolation.
ALT (alanine aminotransferase) is the most liver-specific enzyme. It lives primarily inside liver cells, so when those cells are damaged or inflamed, ALT leaks into the bloodstream. Most labs list the normal range as roughly 7 to 56 U/L, but many gastroenterologists consider truly normal ALT to be closer to 30 U/L for men and 19 U/L for women. This is the number doctors pay the most attention to when screening for liver problems.
AST (aspartate aminotransferase) is found in the liver but also in the heart, muscles, and kidneys. A normal range is typically 10 to 40 U/L. Because AST isn’t exclusive to the liver, an elevated reading can sometimes reflect muscle injury or intense exercise rather than a liver issue.
ALP (alkaline phosphatase) is concentrated in the liver and bones. Normal values are roughly 44 to 147 U/L for adults. Elevated ALP often points toward bile duct problems rather than direct liver cell damage. It can also rise normally during pregnancy or in growing adolescents because of bone activity.
GGT (gamma-glutamyl transferase) has a normal range of 5 to 40 U/L. It’s particularly sensitive to alcohol use and bile duct obstruction. Doctors often order GGT alongside ALP to help figure out whether a high ALP reading is coming from the liver or from bone.
Other Values on Your Liver Panel
Two additional markers commonly appear on liver blood work. They aren’t enzymes, but they reveal how well the liver is actually functioning, not just whether it’s inflamed.
Albumin is a protein the liver produces. A normal level is 3.5 to 5.0 grams per deciliter. Low albumin can signal that the liver has lost enough working tissue that it can’t keep up with protein production, which typically happens in more advanced liver disease.
Bilirubin is a yellow pigment created when old red blood cells break down. The liver processes bilirubin so it can be excreted. A normal total bilirubin level is 0.1 to 1.2 milligrams per deciliter. When bilirubin climbs above normal, it can cause jaundice, the yellowish tint to the skin and eyes that many people associate with liver trouble.
Why Lab Ranges Vary
You may notice that the “normal” range printed on your lab report doesn’t match the numbers listed here exactly. That’s because each laboratory calibrates its equipment differently and sets its own reference ranges based on the local population it serves. A result of 42 U/L might be flagged as high at one lab and normal at another. Always compare your result to the reference range printed on your specific report rather than a number you found online.
Sex and age also shift the goalposts. Men tend to carry higher ALT and AST levels than women. Children and teenagers often have higher ALP because their bones are still growing. Body mass plays a role too: people with higher body weight tend to have slightly higher baseline ALT levels, which can mask early fatty liver disease if doctors rely solely on the lab’s printed cutoff.
What Mild, Moderate, and Severe Elevations Mean
Doctors categorize abnormal liver enzymes by how far above the upper limit of normal (ULN) they climb. A result that’s less than twice the upper limit, say an ALT of 60 when the lab’s cutoff is 40, is considered a mild elevation. The VA’s clinical guidance defines anything under 15 times the upper limit as a mild to moderate elevation. Readings above that threshold (ALT in the hundreds or thousands) suggest acute, severe liver injury from causes like viral hepatitis, drug toxicity, or sudden loss of blood flow to the liver.
A mildly elevated result on a single blood draw is common and not necessarily a sign of serious disease. Exercise, over-the-counter pain relievers, supplements, and even a recent fatty meal can bump the numbers temporarily. When a mild elevation shows up, the typical next step is to simply repeat the test in a few weeks before launching into a larger workup. If the numbers come back normal the second time, it was likely a transient spike.
What the ALT-to-AST Ratio Tells Your Doctor
Beyond the raw numbers, the relationship between ALT and AST helps narrow down the cause of an elevation. In fatty liver disease (NAFLD), ALT is usually higher than AST, giving an AST/ALT ratio below 1. This is the most common pattern doctors see, especially in people with obesity or insulin resistance.
As liver disease progresses and deeper parts of the liver cells become damaged, AST rises relative to ALT, pushing the ratio above 1. This shift is particularly associated with alcohol-related liver disease and advancing fibrosis or cirrhosis. So two people can have the same ALT number, but a flipped ratio tells a very different clinical story. Your doctor will look at this ratio alongside imaging and your medical history to figure out what’s going on.
How to Prepare for a Liver Panel
Most providers ask you to fast for 10 to 12 hours before a liver function blood draw. Water is usually fine, but food and other beverages can affect certain markers, particularly bilirubin and albumin. Let your provider know about every medication and supplement you take, including herbal products, because many of them influence liver enzyme readings. Don’t stop any prescribed medications on your own just to get a “cleaner” result; your doctor needs to see what your liver looks like under your actual daily conditions.
If you work out heavily, mention that too. A hard strength-training session a day or two before the blood draw can raise AST (and sometimes ALT) enough to trigger a false alarm, since those enzymes also spill out of damaged muscle fibers. Some doctors will ask you to avoid intense exercise for 48 hours before the test if a previous result came back borderline.