What does it mean when serum alanine aminotransferase (ALT) is elevated?

Elevated serum alanine aminotransferase (ALT) levels are typically caused by impaired liver function. This is often associated with daily lifestyle habits. For instance, high work-related stress, irregular sleep patterns, and frequent late-night activity can prevent the liver from adequately resting and recovering, thereby increasing the risk of liver damage and subsequent elevation of serum ALT. Additionally, alcohol can cause varying degrees of liver injury; chronic or excessive alcohol consumption may also lead to elevated serum ALT levels.