Alanine Aminotransferase (ALT) Lab Values

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Determine the significance and clinical use of Alanine Aminotransferase in clinical practice


Lab Test Name:

Alanine Aminotransferase – ALT



Measures amount of ALT, an enzyme produced by the liver, present in circulation

Found in:

Most abundantly in liver


Skeletal muscle


Increases in lab values indicate liver disease or liver damage



Evaluation of ALT:

  • Progression of liver disease
  • Monitoring response to treatment


Normal Therapeutic Values:

Normal – 40-130 U/L


  •  Plasma separator tube


What would cause increased levels?


  • Cirrhosis
  • Muscle damage
  • Preeclampsia
  • Biliary tract obstruction
  • Burns
  • Pancreatitis
  • Long-term alcohol abuse
  • Liver Cancer
  • Muscular dystrophy
  • MI
  • Myositis
  • Shock
  • Infection-mononucleosis


What would cause decreased levels?


  • Pyridoxal phosphate deficiency
    • A rare genetic metabolic disorder
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Hi there. This is Abby from This lesson is going to cover alanine aminotransferase. It’s abbreviated as ALT. It’s one of the liver enzymes. We’ll talk about its normal value and conditions, diseases, or even cancers that cause its increase or decrease in lab values. We’ll also talk about normal values. Let’s get started.


Alanine aminotransferase or ALT is a lab that measures the amount of this enzyme in circulation. It’s a liver enzyme and it’s produced most abundantly by the liver, but as well by the heart, skeletal muscle and the kidney. This is an important lab because we need to know what the liver is doing. It indicates to us its function. So, if the normal value is increased, how do you think a patient would present upon assessment? Are you thinking jaundice? You’re right. Yes. A patient with poor liver function will appear with jaundice. That’s one of our signs and symptoms. Now, the reason we use ALT is to monitor the progression of liver disease as well as monitoring response to treatment. The normal value is between 13 and 69 units per liter and here it is on our lab skeleton, of our liver function tests. It’s one of them. This is collected in a plasma separator tube, or as I like to call it, a mint top. Lab values will be increased in the case of liver disease or when there’s biliary at tract obstruction. Major tissue damage like in the case of burns, will also increase this lab value. Those suffering from alcohol abuse disorder will also have elevated liver enzymes. Muscular dystrophy comes into play because remember how we talked about how skeletal muscle produces ALT? Preeclamptic patients will also have an elevation in this lab as well as those that have an infection for mononucleosis. A decrease is pretty rare, and it takes place in the case of pyridoxal phosphate deficiency. This is a rare metabolic disorder that’s genetic. 


Our linchpins for this lesson are that ALT is an enzyme that is quantified in the blood with this lab value. It’s one of the LFTs or liver function tests. A normal value is between 13 and 69 units per liter and when increased, indicates liver disease or muscle damage. A decreased value means pyridoxal phosphate deficiency again, a rare genetic metabolic disorder. 


You all did so great on this lesson. Great job. That wraps it up. We love you guys, now go out and be your best self today and as always, happy nursing!


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