The Serum Alt: Frequently Asked Questions

What is it?

The ALT is a protein manufactured in the liver which participates in metabolism.  The term ALT refers to alanine-amino transferase. This protein is an enzyme which participates in modifying aminoacids, the building blocks of proteins. The ALT is made predominately in the liver and therefore alterations in the serum ALT can be directly related to disturbances of liver structure and function.

Is the serum ALT hard to measure?

It is straightforward to have ones blood sample tested for a serum ALT, it only requires obtaining a blood sample. The serum ALT is easily measured in laboratories throughout the world. The methodology may vary from laboratory to laboratory, making direct comparisons of the absolute serum ALT value difficult, but all laboratories have a normal range for men and women. 

What does an elevated serum ALT reflect?

The ALT is manufactured within liver cells. Elevations in the serum ALT reflect alterations in the structure and function of the liver.  Damaged liver cells release ALT into the blood stream where it can then be measured. The serum ALT, therefore, reflects damage to liver cells, liver injury, and underlying liver disease.

Why should I know my serum ALT?

We should all be aware of our health. Unfortunately, unlike diseases affecting other organs, injury to the liver can be silent. Patients may not have any symptoms and the ALT can be elevated for years before one is aware of an underlying liver disease. When one develops symptoms from liver disease, it usually reflects advanced damage to the liver. Once significant damage to the liver has occurred, therapies other than liver transplantation, may not be very beneficial. Therefore, making the diagnosis of a liver disease early in its course can be very beneficial in regards to receiving specific therapies and modifying lifestyle.

My doctor also measures other blood tests. What are they and is the serum ALT the best test?

The liver is a complex organ with a variety of essential functions for the body. It participates in metabolism, produces bile, and generates proteins secreted into the blood, so your doctor may measure compounds associated with all of these liver functions. All of those tests are frequently measured in a battery of tests referred to as a “liver panel.” Depending upon the type and nature of the underlying liver injury and therefore the liver disease, changes in the magnitude of the various components of this panel provide meaningful information to your physician. However, if one simply wants to know whether one has liver wellness or may have an underlying liver disease, the ALT is likely the most sensitive test for the vast majority of liver illness.

Is there a direct correlation between the magnitude of the serum ALT elevation and the severity of the underlying liver disease?

Although there can be a relationship between the magnitude of elevation in the serum ALT and the severity of the abnormalities in liver structure and function, this relationship is not absolute. Patients with advanced scarring of the liver may have significant liver dysfunction despite only mild elevations of the serum ALT. Therefore, any elevation of the serum ALT should be taken seriously and one should seek appropriate medical care to determine the cause.

What are some common causes of an elevated serum ALT?

Perhaps the most common cause in the North American population is fat accumulation within liver cells. Fat can accumulate anywhere in the body, but its accumulation in the liver cells is toxic to the liver. In particular, patients who are above their ideal body weight, have diabetes, or elevations in their blood lipids, may be at risk for having fat within the liver. The serum ALT is a common approach to determine whether one may have fat in the liver and if it is injurious to this organ. Other common causes of an elevated serum ALT include excessive consumption of alcohol, infection by chronic hepatitis viruses such as hepatitis B and C, toxicity from pharmaceutical medications, a genetic liver disease associated with an excess accumulation of iron in the liver, and autoimmune liver diseases.  The latter are a variety of liver diseases in which the body’s immune system inflicts damage on ones own organ.

I have an elevated ALT. What should I do?

If you have an elevated ALT, you should seek medical attention. The vast majority of primary care physicians and specialists in gastroenterology and hepatology, can perform the necessary testing to determine the cause of an elevated serum ALT.

How often should I have my serum ALT measured?

Like the serum cholesterol and blood glucose tests for elevated cholesterol and diabetes, respectively; one should have the serum ALT measured repeatedly and regularly over time. A conservative approach would be to have ones serum ALT measured on an annual basis during the annual physical examination