ALT Blood Test: What Is It & Normal Range

ALT test, also known as alanine aminotransferase test or SGPT blood test, is a type of exam that helps to identify damage and diseases of the liver, due to the elevated presence of this enzyme in the blood.

Alanine aminotransferase (ALT) is a type of enzyme that is found inside the liver cells and, so, when there is damage to the liver, it is normal for large amounts of the enzyme to be released into the bloodstream, leading to an increase in the ALT blood test results.

ALT Blood Test: What Is It & Normal Range

When to do an ALT blood test

The ALT blood test is used to detect liver damage and, so, it can be recommended for people who have a fatty liver or that are overweight. It is also recommended when there are symptoms such as:

  • Excessive tiredness;
  • Loss of appetite; 
  • Nausea;
  • Vomiting;
  • Swelling of the belly;
  • Dark urine;
  • Yellow skin and eyes.

An ALT blood test is a great tool to diagnose liver problems early on. Therefore an ALT test can also be requested when there is history of exposure to some type of hepatitis virus or excessive consumption of alcohol.

Normal range results

ALT levels are considered normal between 7 - 56 UI/L. If the test result shows a higher value, it can be indicative of:

High levels of ALT

  •  4x higher than normal: is normally a sign of chronic hepatitis caused by cirrhosis or cancer.

Very high levels of ALT

  • 10x higher than normal: is usually a change caused by acute hepatitis due to viruses or the use of drugs;
  • 100x higher than normal: is very common in people who use drugs, alcohol or other substances that cause severe liver damage.

Despite being a very specific marker for liver damage, ALT can also be found in muscles and in the heart tissue. Therefore an increase in the concentration of this enzyme can also be seen after intense physical exercises.

To assess liver function and identify any damage, the doctor may also request other types of blood test to check for other enzymes, such as lactate dehydrogenase (LDH) and AST (or SGOT). 

What to do if ALT levels are high

When ALT levels are high it is recommended to consult with a hepatologist to assess your clinical history and identify what may be causing damage to the liver. The doctor may also request other more specific tests such as hepatitis tests or a liver biopsy, to confirm a diagnostic hypothesis.

Furthermore, in cases of high ALT, it is also recommended to follow an adequate diet for the liver, which should be low in fats and giving preference to boiled foods. 

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