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Prolactin (Blood)

Does this test have other names?

PRL test

What is this test?

This test measures the level of prolactin in your blood. Prolactin is a hormone made by the pituitary gland, which is in your brain. In women who are pregnant, prolactin stimulates the breasts to make breastmilk.

If the prolactin-making cells in your pituitary gland begin to change (mutate) and grow out of control, they can form tumors (prolactinomas). Prolactinomas, also known as lactotroph adenomas, are usually not cancerous. They happen most often in women younger than 50. One symptom of a prolactinoma tumor is producing breastmilk even if you're not pregnant. In men, prolactinomas may cause impotence or lower sex drive.

If you are diagnosed with a prolactinoma, your healthcare provider may give you a medicine called a dopamine agonist, such as bromocriptine or cabergoline. Cabergoline works well and has been shown to cut prolactin levels in roughly 90% of people with prolactinomas. Cabergoline also reduces the size of prolactinoma tumors.

Why do I need this test?

You may need this test if your healthcare provider suspects that you have a prolactinoma tumor. Symptoms of this type of tumor include:

  • Flow of breastmilk in a woman who's not pregnant or nursing

  • Breast tenderness in women

  • Enlarged breasts in men

  • Lower sex drive

  • Headache

  • Impotence in men

  • Vision changes

What other tests might I have along with this test?

Your healthcare provider may also order an MRI scan of your brain to check for a prolactinoma. You may also need blood tests to look for other hormones made by the pituitary gland. These include thyroid-stimulating hormone, luteinizing hormone, and follicle-stimulating hormone.

What do my test results mean?

Test results may vary depending on your age, gender, health history, the method used for the test, and other things. Your test results may not mean you have a problem. Ask your healthcare provider what your test results mean for you. 

Results are given in micrograms per liter (µg/L). A normal blood level of prolactin is less than 20 µg/L. If your test result shows an abnormally high prolactin level, you may need imaging tests to find out whether you have a prolactinoma tumor.

How is this test done?

The test is done with a blood sample. A needle is used to draw blood from a vein in your arm or hand. 

Does this test pose any risks?

Having a blood test with a needle carries some risks. These include bleeding, infection, bruising, and feeling lightheaded. When the needle pricks your arm or hand, you may feel a slight sting or pain. Afterward, the site may be sore. 

What might affect my test results?

Certain psychiatric medicines, oral estrogen drugs, and hypothyroid medicines may cause prolactin levels to be higher than normal. If you have kidney or liver disease, you may also have high prolactin levels.  

How do I get ready for this test?

You don't need to prepare for this test. Be sure your healthcare provider knows about all medicines, herbs, vitamins, and supplements you are taking. This includes medicines that don't need a prescription and any illicit drugs you may use. 

Medical Reviewers:

  • Freeborn, Donna, PhD, CNM, FNP
  • Haldeman-Englert, Chad, MD