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Am Fam Physician. 2017;96(11):online

See related article on elevated liver transaminase levels

What are liver enzymes?

The liver releases several substances when it is injured. Two of these substances are enzymes called alanine transaminase (ALT) and aspartate transaminase (AST).

What causes elevated ALT and AST levels?

There are many causes of mildly elevated ALT and AST levels. The most common causes are nonalcoholic fatty liver disease (NAFLD) and alcoholic liver disease. In NAFLD, the liver has more fatty tissue in it than normal. Regular or heavy alcohol use can also hurt the liver and increase liver enzymes. Other medical conditions can increase liver enzymes, like hepatitis B or C and a condition that runs in families called hemochromatosis. Using certain medicines and over-the-counter supplements can also increase liver enzymes.

What are the symptoms?

People with mild elevations in liver enzymes usually do not have symptoms.

What will my doctor do?

Your doctor will ask you questions and examine you to try and find out why your liver enzymes are elevated. He or she may also do blood tests. A scan of your liver, called an ultrasound, might help your doctor find a cause.

How is it treated?

It depends on what is causing your liver enzymes to be elevated. If your doctor thinks you have NAFLD, you will need to make lifestyle changes. These changes include eating a healthier diet, exercising, losing weight, and limiting alcohol and sugary foods and drinks.

What if a cause isn't found or my liver enzymes stay elevated?

Your doctor may do further testing. You may need to see a specialist who can check for less common causes. Your doctor may also take a small piece of your liver for testing. This is called a biopsy.

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