Normal prolactin levels for men range from 3 to15 nanograms per milliliter or 3 to15 micrograms per liter. For nonpregnant women, the range is 4 to 23 nanograms per milliliter or 4 to 23 micrograms per liter, according to WebMD.
For pregnant women, the normal prolactin range is 34 to 386 nanograms per milliliter or 34 to 386 micrograms per liter. For children, normal prolactin levels are 3.2 to 20 nanograms per milliliter or 3.2 to 20 micrograms per liter, says WebMD.
Prolactin is a hormone secreted by the pituitary gland, states Healthline. While it is important to the reproductive health of both men and women, prolactin's main job is to induce lactation in women after childbirth. Prolactin levels vary throughout the day, notes WebMD. They are highest during sleep and shortly after rising.
High prolactin levels outside of pregnancy can indicate a pituitary gland tumor called a prolactinoma, states WebMD. These benign tumors are treated with surgery to remove the entire pituitary gland or with radiation therapy. The health and age of the patient and the size of the tumor dictate the treatment choice.
Other conditions that can cause elevated prolactin levels include hypothyroidism, kidney and liver disease and pregnancy, states WebMD. Low prolactin levels can be caused by Sheehan syndrome, in which a woman's pituitary gland is damaged during childbirth due to excessive blood loss and shock, states the Merck Manual.