Alanine aminotransferase (ALT) is an enzyme primarily found in liver cells. Its measurement in a blood test serves as a common marker for liver health. When liver cells are damaged, ALT can leak into the bloodstream, indicating potential liver injury or inflammation.
What is ALT?
ALT is an enzyme crucial for the body’s metabolism, specifically involved in converting alanine, an amino acid, into pyruvate, a molecule used for energy production. While ALT is predominantly concentrated in the liver, smaller amounts are also present in other tissues like the kidneys, heart, and muscles. The liver utilizes enzymes like ALT to break down proteins, aiding their absorption by the body.
Normally, levels of ALT in the blood are low. However, when liver cells become irritated or damaged, they release excess ALT into the bloodstream. This increased leakage of ALT into the blood signals potential damage or inflammation within the liver. Therefore, an ALT blood test is a valuable tool healthcare providers use to assess the health of the liver.
What Are Normal ALT Levels?
The “normal” range for ALT levels in a blood test can vary slightly among different laboratories, as each lab establishes its own reference values. A commonly accepted reference range for ALT is typically between 7 and 56 units per liter (U/L). For males, the healthy range is often cited as 7 to 55 U/L, while for females, it may be 7 to 45 U/L, as ALT levels are generally higher in men.
Age can also influence ALT levels, with levels tending to decrease in older individuals. Your test report will include the specific reference range used by the laboratory that performed your test.
Understanding Abnormal ALT Results
When ALT levels in a blood test fall outside the normal range, it often indicates a potential issue, most commonly liver damage or disease. Elevated ALT levels can stem from various causes, including fatty liver disease, which involves too much fat accumulating in the liver. Other common reasons for high ALT include viral hepatitis (such as hepatitis A, B, or C), alcohol-induced liver injury, and certain medications that can be toxic to the liver.
Liver conditions like cirrhosis, characterized by scarring of the liver, or liver ischemia, where there isn’t enough blood flow to the liver, can also lead to increased ALT. A slight increase might also be temporary due to vigorous exercise or a fatty meal before the test. Less commonly, elevated ALT can indicate damage to other tissues like the heart or muscles, as a small amount of ALT is found there. Conversely, lower-than-normal ALT levels are uncommon and usually not a significant concern, though they can sometimes be associated with conditions like vitamin B6 deficiency or chronic kidney disease.
What to Do After an ALT Test
An abnormal ALT test result does not automatically mean a severe medical condition is present. Many factors can influence ALT levels, and about 1 in 20 healthy individuals may have results outside the typical range. Consult a healthcare professional to interpret your results, as an isolated ALT level does not provide a complete diagnosis.
Your doctor may recommend further blood tests, such as other liver function tests or imaging studies like an ultrasound, to investigate the underlying cause. Lifestyle adjustments can often help maintain healthy liver function and potentially normalize ALT levels. These changes may include adopting a balanced diet, limiting alcohol consumption, engaging in regular exercise, and managing weight. For instance, reducing saturated fats, trans fats, and carbohydrates can support liver health, and consistent physical activity can help burn triglycerides and reduce liver fat.