Prolactin is a hormone released by the pituitary gland. The prolactin test measures the amount of prolactin in the blood.
How the Test is Performed
Blood is typically drawn from a vein, usually from the inside of the elbow or the back of the hand. The site is cleaned with germ-killing medicine (antiseptic). The health care provider wraps an elastic band around the upper arm to apply pressure to the area and make the vein swell with blood.
Next, the health care provider gently inserts a needle into the vein. The blood collects into an airtight vial or tube attached to the needle. The elastic band is removed from your arm. Once the blood has been collected, the needle is removed, and the puncture site is covered to stop any bleeding.
In infants or young children, a sharp tool called a lancet may be used to puncture the skin and make it bleed. The blood collects into a small glass tube called a pipette, or onto a slide or test strip. A bandage may be placed over the area if there is any bleeding.
How to Prepare for the Test
No special preparation is necessary.
How the Test Will Feel
When the needle is inserted to draw blood, some people feel moderate pain, while others feel only a prick or stinging sensation. Afterward, there may be some throbbing.
Why the Test is Performed
Prolactin is a hormone released by the pituitary gland that stimulates breast development and milk production in women. There is no known normal function of 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)
- Irregular or no menstrual periods (amenorrhea)
The normal values for prolactin are as follows:
- Males: 2 - 18 ng/mL
- Nonpregnant females: 2 - 29 ng/mL
- Pregnant women: 10 - 209 ng/mL
Normal value ranges may vary slightly among different laboratories. Talk to your doctor about the meaning of your specific test results.
The examples above show the common measurements for results for these tests. Some laboratories use different measurements or may test different specimens.
Note: ng/mL = nanograms per milliliter
What Abnormal Results Mean
People with the following conditions may have high prolactin levels:
- Chest wall trauma or irritation
- Hypothalamic disease
- Kidney disease
- Pituitary tumor that makes prolactin (prolactinoma)
- Other pituitary tumors and diseases
Certain medications can also raise prolactin levels, including:
- H2 blockers
If your prolactin levels are high, the test may be repeated in the early morning after an 8-hour fast.
Veins and arteries vary in size from one patient to another and from one side of the body to the other. Obtaining a blood sample from some people may be more difficult than from others.
Other risks associated with having blood drawn are slight but may include:
- Excessive bleeding
- Fainting or feeling light-headed
- Hematoma (blood accumulating under the skin)
- Infection (a slight risk any time the skin is broken)
The following can temporarily increase prolactin levels:
- Emotional or physical stress (occasionally)
- High-protein meals
- Intense breast stimulation
- Recent breast exam
- Recent exercise
Melmed S, Kleinberg D. Anterior pituitary. In: Kronenberg HM, Melmed S, Polonsky KS, Larsen PR, eds. Williams Textbook of Endocrinology. 11th ed. Philadelphia, PA: Saunders Elsevier; 2008:chap 8.
Ari S. Eckman, MD, Division of Endocrinology and Metabolism, Johns Hopkins School of Medicine, Baltimore, MD. Review provided by VeriMed Healthcare Network. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc.
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