Aspartate aminotransferase (AST) and alanine aminotransferase (ALT)are two of the liver enzymes healthcare providers look at when trying to figure out if you have a problem with your liver. Liver enzymes are substances produced by the liver that can be measured with a blood test. High ALT levels or high AST levels may be a sign of a liver problem. Show
When compared to each other, ALT and AST levels can help identify toxins in the liver, liver disease, or liver damage. This article will discuss ALT and AST liver enzymes and what they do inside your body. It will also cover what happens during testing and what test results can reveal.  Verywell / Elise Degarmo When Testing Is RecommendedALT and AST levels are measured as part of a comprehensive testing panel known as the liver function test (LFT). An LFT may be ordered:
An LFT can also determine whether a drug (prescription or over-the-counter) or an herbal remedy is causing liver injury. If the lab test is processed on-site, the results can be returned within hours. Otherwise, your doctor will usually receive the results in anywhere from one to three days. Roles of AST and ALTAminotransferases are chemicals the liver uses to make glycogen. Glycogen is the stored form of glucose, the sugar that the body uses for energy. Any glucose not immediately used will be changed into glycogen. It is then stored in cells for future use. Most will be stored in the liver. The leftover amount will be warehoused in the:
Aspartate aminotransferase (AST) is found in a variety of tissues, including the liver, brain, pancreas, heart, kidneys, lungs, and skeletal muscles. If any of these tissues are damaged, AST will be released into the bloodstream. While high AST levels mean there may be tissue injury, it doesn't always relate to the liver. By contrast, alanine aminotransferase (ALT) is found mainly in the liver. High ALT levels are always worrying, but they don't necessarily point to something serious. If your ALT level is high, it may indicate minor or severe liver injury. Occasional
increases in ALT may occur when you have a short-term infection or illness. Sustained increases are more serious. That's because this may mean there's an underlying disease and a greater chance of liver damage. What Happens During TestingALT/AST levels are usually measured as part of a liver function test. This is a simple blood test, which may be done at a lab or hospital or in your healthcare provider's office. Preparing for the TestThis test usually requires a period of fasting prior to the blood draw. This means you will be asked not to eat anything up to 12 hours before you arrive. Ask your healthcare provider if you need to stop taking any of your medications prior to the test. During the TestYou will be asked to roll up your sleeve and expose the bend in your elbow. Your healthcare provider will clean the area and place a tight band around your arm above your elbow. You will be asked to make a fist to help make the vein easier to find. You may feel a pinch when the needle is inserted. Your healthcare provider will place gauze over the site after the sample has been taken. After the TestIt's possible you may feel lightheaded immediately after the test. If so, wait until you feel better before attempting to drive home. You may have slight bruising where your blood was drawn. The area may feel sore for a day or two. Normal Lab ValuesAST and ALT are measured in international units per liter (IU/L). The normal levels vary based on a person's body mass index (BMI) It also depends on the lab's reference value, or typical results. Generally speaking, a normal AST level for adults is: 8 to 48 IU/L. A normal ALT level for adults is 7 to 55 IU/L. The high end of the reference range is referred to as the upper limit of normal (ULN). This number is used to establish how elevated your liver enzymes are. Mild elevations are generally considered to be two to three times the ULN. With some liver diseases, the level can be more than 50 times the ULN. Levels this high are described as deranged. AST/ALT RatioWhile it may seem that a high ALT is all that is needed to diagnose liver disease, its relationship to AST can provide valuable clues as to what exactly is going on. It will also tell you whether the issue is acute (occurring suddenly and progressing rapidly) or chronic (long-standing or persistent). If the liver experiences an acute injury, you can expect to see a sudden spike in the ALT. On the other hand, if liver disease is slowly progressing, the damage in the liver will gradually affect other organs too. As these organs are damaged, the AST will begin to rise. This occurs with diseases like hepatitis C. It causes long-term liver damage that triggers symptoms involving:
These are referred to as extra-hepatic symptoms. The relationship between these enzymes is described using the AST/ALT ratio. This is a calculation that compares the levels of AST and ALT in your blood. Depending on which value is elevated and the amount of elevation, doctors can often get a pretty strong indication as to what disease is involved. What the AST/ALT Ratio RevealsThe AST/ALT ratio is important because its pattern can tell a lot about the condition involved. Here are the general guidelines used to diagnose liver disease:
However, a disease cannot be diagnosed by the pattern of elevation alone. How elevated the levels are also needs to be measured. This is described in multiples of the ULN. It is only when the levels are above a certain threshold that the ratio can be considered diagnostic. RecapThe AST/ALT ratio is a comparison of the levels of the two enzymes. This measurement can point to liver diseases, but only if the enzyme levels are elevated several times above normal. SummaryALT and AST liver enzymes are produced by the liver. Doctors can test these levels with a blood test. If you have elevated liver enzymes, it could be a sign that you have liver disease. AST is found in the liver, brain, pancreas, heart, kidneys, lungs, and skeletal muscles. ALT is found mainly in the liver. If your AST levels are too high, it might be a sign of an injury affecting tissues other than the liver. High ALT levels may mean you have a liver injury. It could also be a sign that you have an infection or short-term illness. The ratio of the two enzymes can help diagnose specific liver diseases. Frequently Asked Questions
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Charles Daniel Thanks for your feedback! When should I worry about high ALT?What ALT level is considered high? The upper limit of normal for ALT is 55 IU/L. When an ALT level is double to triple the upper limit of normal, it is considered mildly elevated. Severely elevated ALT levels found in liver disease are often 50 times the upper limit of normal.
What should I do if my ALT is high?People can lower their ALT levels by making lifestyle changes, such as taking regular exercise and changing their diet. Increasing fiber intake, reducing saturated fats and processed foods, as well as consuming a range of nutrients from fruits and vegetables may all help to lower levels.
What level of ALT is concerning?An ALT test result of >100 IU/l is a clear indicator of serious liver disease, but a mildly elevated ALT result (30–100 IU/l) is often ascribed to the use of medication (for example statins) or alcohol, obesity, or, for lower ALT levels (<50 IU/l), considered as part of the normal distribution of test results.
Should I worry if my alanine aminotransferase is high?High levels of ALT in your blood can be due to damage or injury to the cells in your liver. An increased ALT level may indicate the following conditions: Alcohol-induced liver injury. Fatty liver disease (too much fat in your liver).
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What does it mean if your alanine aminotransferase is high
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