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ALT blood test: what is it and how to interpret the results

The alanine aminotransferase test, also known as ALT or GPT blood test, is a type of exam that helps to identify damage and diseases of the liver, due to the elevated presence of the enzyme alanine aminotransferase in the blood, which is normally found between 7 and 56 U/L of blood.

This enzyme is present inside the liver cells and, so, when there is damage to this organ because of a virus or toxic substances, for example, it is common for the enzyme to be released into the bloodstream, leading to an increase in your blood test levels. This can mean:

ALT blood test: what is it and how to interpret the results

Very high levels of ALT

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

High levels of ALT

  •  4 times higher than normal: can be a sign of chronic hepatitis and, so, it can indicate liver disease such as cirrhosis or cancer.

Despite being a very specific marker for liver damage, this enzyme can also be found in the muscles and the heart in a lesser amount, and, therefore, an increase in the concentration of this enzyme in the blood can be seen after intense physical exercises. To assess liver function and identify any damage, the doctor may also request another blood test to checkother enzymes, such as lactate dehydrogenase (LDH) and AST (or GOT). 

What to do in case of high ALT

In cases where the ALT blood test has a high value, it is recommended to seek a hepatologist to assess the clinical history and identify what may be the cause of the change to the liver. This doctor may also request other more specific tests such as hepatitis tests or a liver biopsy, to confirm the diagnostic hypothesis.

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

ALT blood test: what is it and how to interpret the results

When to do the ALT test

The ALT blood test is used to detect liver damage and, so, it can be recommended for people who have:

  • Liver fat or are overweight;
  • Excessive tiredness;
  • Loss of appetite; 
  • Nausea;
  • Vomiting;
  • Swelling of the belly;
  • Dark urine;
  • Yellow skin and eyes.

However, ALT levels may already be high even when the patient doesn't have any symptoms, so it's a great tool to diagnose liver problems early on. In this way, the ALT test can also be done when there is a history of exposure to the hepatitis virus, excessive use of alcoholic beverages or the presence of diabetes.

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