Normal Bilirubin But High AST and ALT: What Does It Mean?

In this article, we will take a close look at the relationship between aspartate aminotransferase (AST), alanine aminotransferase (ALT), and bilirubin levels. We will discuss how it's possible to have high AST and ALT levels with normal bilirubin, and what this could mean in terms of liver disease or damage.

Author - Jakub Gwiazdecki

Fifth year medical student at the Medical Faculty of Comenius University in Bratislava.

Jakub used MediSearch to find sources for this blog.

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Is it possible to get high AST and ALT with normal bilirubin?

Yes, it is possible to have high levels of aspartate aminotransferase (AST) and alanine aminotransferase (ALT) with normal bilirubin levels.

High levels of AST and ALT can indicate liver disease or damage. The levels of bilirubin can be normal, especially early in the process.

What does it mean when bilirubin is normal but AST and ALT are high?

High levels of AST and ALT are enzymatic markers that indicate liver problems. Their high concentration indicates liver cell damage or death.

In the early stage of a liver disease, bilirubin can have ordinary values. As liver problems begin, bilirubin will build up, and bilirubin values will increase. However, this can take a few days of time.

Among the conditions that can lead to increased AST and ALT are:

chronic alcohol consumption [1],
drug use [1],
non-alcoholic steatohepatitis [1],
chronic viral liver infection [1],
hemochromatosis [2],
ischemic disease of the liver [2],
autoimmune hepatitis [2],
liver injury caused by herbal supplement [2].

Also, other conditions can lead to increased AST and ALT levels. Among them are acute muscle injury, polymyositis, hypothyroidism, and acute myocardial infarction [1].

However, in cases that do not affect the liver, the increased levels of AST and ALT will be accompanied by other biochemical markers. In acute muscle injury, for instance, creatinine kinase, lactate dehydrogenase, and myoglobin will be increased.

What are AST and ALT?

AST stands for aspartate aminotransferase, and ALT for alanine aminotransferase. Both AST and ALT are enzymes responsible for amino acid metabolism.

AST and ALT are present in the whole body. However, their highest concentration is in the liver. Therefore, in the clinic, these enzymes are used as liver markers. Out of them two, ALT is more liver-specific than AST [3, 4].

Can certain foods increase AST and ALT?

Yes, intake of specific substances can increase the levels of AST and ALT in the blood.

Here are examples of such foods.

High fat consumption, particularly of saturated and trans fats, can lead to an increase in AST and ALT [5].
Drinking a lot of coffee can increase the AST and ALT levels [6].
Eating high-energy-density meals, like fast foods, can cause an increase in ALT levels [7].

Additionally, high soybean consumption was found to increase levels of AST and ALT [8].

However, this study was on rats. Therefore, the impact soybeans have on humans may be different.

What are the normal values of AST and ALT?

The normal values of AST and ALT vary depending on the population and the measurement method.

According to the American Board of Internal Medicine, the standard values are at 0 to 40 UI/L for AST and ALT [9].

Sometimes, the result may be close to the norm. In such cases, you do not have to worry yet. Your clinic should repeat the blood test to minimize the chance of any technical mistakes.

A warning sign is a value of or three times the upper limit. This would indicate serious liver problems.