PRL levels are typically reported in units such as nanograms per milliliter (ng/mL) or micrograms per liter (μg/L). Prolactin levels can vary throughout the day and are influenced by factors such as stress, sleep, and certain medications.

Measuring PRL levels can be helpful in diagnosing and monitoring conditions related to prolactin dysfunction. High levels of PRL, known as hyperprolactinemia, can be associated with conditions such as prolactinoma (a benign tumor of the pituitary gland), hypothyroidism, polycystic ovary syndrome (PCOS), and certain medications. Low levels of PRL are less common and can be associated with conditions such as pituitary dysfunction or hypothalamic disorders.