A fasting blood sample is needed.

No special preparation is necessary.

When the needle is inserted to draw blood, some people feel moderate pain. Others feel only a prick or stinging. Afterward, there may be some throbbing or a slight bruise. This soon goes away.

Prolactin is a hormone released by the pituitary gland. The pituitary is a small gland at the base of the brain. It regulates the body's balance of many hormones.

Prolactin stimulates breast development and milk production in women. There is no known normal function for prolactin in men.

Prolactin is usually measured when checking for pituitary tumors and the cause of:

• Breast milk production that is not related to childbirth (galactorrhea)
• Decreased sex drive (libido) in men and women
• Erection problems in men
• Not able to get pregnant (infertility in women)
• Irregular or no menstrual periods (amenorrhea)

The normal values for prolactin are:

• Men: less than 20 ng/mL (20 µg/L)
• Nonpregnant women: less than 25 ng/mL (25 µg/L)
• Pregnant women: less than 500 ng/mL (500 µg/L)

Normal value ranges may vary slightly among different laboratories. Some labs use different measurements or test different samples. Talk to your health care provider about the meaning of your specific test results.

People with the following conditions may have high prolactin levels:

• Chest wall injury or irritation
• Presence of nipple rings
• Disease of an area of the brain called the hypothalamus
• Thyroid gland does not make enough thyroid hormone (hypothyroidism)
• Kidney disease
• Pituitary tumor that makes prolactin (prolactinoma)
• Other pituitary tumors and diseases in the area of the pituitary
• Abnormal clearance of prolactin molecules (macroprolactin)

Certain medicines can also raise prolactin level, including:

• Antidepressants
• Butyrophenones
• Estrogens
• H2 blockers
• Metoclopramide
• Opioid medicines
• Phenothiazines
• Risperidone
• Verapamil

Marijuana products can also raise prolactin level.

If your prolactin level is high, the test may be repeated in the early morning after an 8-hour fast.

The following can temporarily increase prolactin levels:

• Emotional or physical stress (occasionally)
• High-protein meals
• Intense breast stimulation
• Recent breast exam
• Recent exercise

Interpretation of an abnormally high prolactin blood test is complicated. In most case, your provider will need to refer you to an endocrinologist, a doctor who specializes in hormone problems.

There is little risk in having your blood taken. Veins and arteries vary in size from one person to another and from one side of the body to the other. Taking blood from some people may be more difficult than from others.

Other risks associated with having blood drawn are slight, but may include:

• Excessive bleeding
• Multiple punctures to locate veins
• Fainting or feeling lightheaded
• Hematoma (blood buildup under the skin)
• Infection (a slight risk any time the skin is broken)

PRL; Galactorrhea - prolactin test; Infertility - prolactin test; Amenorrhea - prolactin test; Breast leakage - prolactin test; Prolactinoma - prolactin test; Pituitary tumor - prolactin test

Guber HA, Oprea M, Rusell YX. Evaluation of endocrine function. In: McPherson RA, Pincus MR, eds. Henry's Clinical Diagnosis and Management by Laboratory Methods. 24th ed. Philadelphia, PA: Elsevier; 2022:chap 25.

Weiss RE. Anterior pituitary. In: Goldman L, Cooney KA, eds. Goldman-Cecil Medicine. 27th ed. Philadelphia, PA: Elsevier; 2024:chap 205.

Updated by: Sandeep K. Dhaliwal, MD, board-certified in Diabetes, Endocrinology, and Metabolism, Springfield, VA. Also reviewed by David C. Dugdale, MD, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team.