Alanine aminotransferase (ALT) is a liver enzyme frequently measured during routine blood tests. An elevated ALT level can be concerning, prompting questions about its meaning. This article clarifies the significance of high ALT, exploring its origins and next steps.
What is ALT
Alanine aminotransferase (ALT) is an enzyme found predominantly within liver cells. ALT plays a specific role in liver metabolism by helping convert food into energy. While present in other tissues, elevated ALT in the bloodstream primarily signals processes occurring within the liver.
What High ALT Means
Elevated levels of ALT in the blood usually indicate that liver cells have experienced some form of damage or inflammation. When liver cells are injured, ALT leaks from these damaged cells into the bloodstream, resulting in higher measurable concentrations. A high ALT level serves as an indicator of a potential liver issue, but it is not a specific diagnosis on its own. For instance, a mild elevation might be due to recent vigorous exercise or a fatty meal. Further medical investigation is always necessary to pinpoint the exact underlying cause.
Laboratories typically define a “normal range” for ALT, with values significantly above this range considered elevated. While normal ranges can vary slightly between different laboratories, a common reference range for adults is approximately 7 to 56 units per liter (U/L). The American Association for the Study of Liver Diseases (AASLD) suggests an upper limit of normal around 35 IU/L for men and 25 IU/L for women. Mild elevations are generally considered 2-3 times higher than the normal range, while severe elevations can reach levels in the thousands, suggesting more significant damage.
Common Reasons for High ALT
Several common conditions can lead to elevated ALT levels, reflecting various forms of liver stress or injury. Non-alcoholic fatty liver disease (NAFLD), now often referred to as metabolic dysfunction-associated steatotic liver disease (MASLD), is a frequent cause, where fat accumulation in the liver can lead to inflammation and cell damage. This condition is closely linked to obesity and metabolic syndrome, where insulin resistance and dyslipidemia contribute to liver fat accumulation.
Alcoholic liver disease, resulting from excessive alcohol consumption, also commonly causes elevated ALT. In this condition, the liver’s ability to process alcohol is overwhelmed, leading to fat buildup, inflammation, and potential scarring. Viral hepatitis, such as Hepatitis A, B, or C, directly infects and inflames liver cells, often causing significant increases in ALT. Certain medications can also induce liver injury, including some over-the-counter pain relievers like acetaminophen, statins used for cholesterol management, and various antibiotics.
Autoimmune hepatitis involves the body’s immune system mistakenly attacking its own liver cells, leading to inflammation and elevated ALT. Mononucleosis, a viral infection, can also cause liver inflammation and elevated ALT levels, typically resolving as the infection clears. Less common conditions, such as hemochromatosis, where too much iron accumulates in the body and can damage the liver, and alpha-1 antitrypsin deficiency, a genetic disorder causing misfolded proteins to build up in liver cells, are also recognized causes of elevated ALT.
What to Do After a High ALT Result
Receiving a high ALT result emphasizes the importance of consulting a healthcare professional. A doctor can properly interpret the result within the context of an individual’s overall health, medical history, and other symptoms. Further evaluation is typically needed.
A healthcare provider might order additional diagnostic tests to determine the cause of the elevated ALT. These could include repeating the ALT test, performing other liver function tests to assess different aspects of liver health, or ordering imaging studies like an ultrasound to visualize the liver. In some cases, specific viral hepatitis panels or a liver biopsy may be recommended to gain a clearer understanding of the liver’s condition and the underlying cause.
While awaiting a professional diagnosis, a doctor might suggest general lifestyle modifications. These can include limiting or avoiding alcohol intake, adopting a healthy and balanced diet rich in fruits, vegetables, and whole grains, and engaging in regular physical exercise. Weight management is also often recommended, particularly for individuals with obesity or metabolic syndrome, as it can significantly improve liver health. However, any changes to diet or lifestyle should always be undertaken under the guidance of a healthcare professional.