Prolactin (Blood)

PRL 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 grow out of control, they can form tumors (prolactinomas). Prolactinomas, also known as lactotroph adenomas, are often not cancer. 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 trouble getting or keeping an erection (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 most people with prolactinomas. Cabergoline also reduces the size of prolactinoma tumors.

You may need this test if your healthcare provider believes 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 soreness in women

• Enlarged breasts in men

• Lower sex drive

• Headache

• Impotence in men

• Vision changes

You may also need 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.

Test results may vary depending on your age, gender, health history, and other things. Your test results may be different depending on the lab used. They 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 in a nonpregnant woman is less than 20 µg/L. In men, the normal level is less than 15µg/L. If your test result shows an abnormally high prolactin level, you may need imaging tests to find out if you have a prolactinoma tumor.

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

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. 

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

You will need to fast (not eat or drink anything but water) for about 12 hours before the 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 illegal drugs you may use.