Prolactin Levels
Reviewed
Also called: PRL test, Prolactin blood test
A prolactin test measures the level of prolactin in your blood. Prolactin is a hormone that mainly signals breast tissue to grow during pregnancy and produce milk for breastfeeding. Levels are normally high in pregnant and breastfeeding women and low in nonpregnant women and men.
Specimen: Blood
Why this test may be ordered
- To help diagnose a prolactinoma (a benign pituitary tumor)
- To find the cause of irregular menstrual periods or infertility in women
- To find the cause of infertility, low sex drive, or erectile dysfunction in men
- To monitor a known prolactinoma and check if treatment is working or if the tumor has returned
Preparation and collection
Your provider will let you know if you need to fast (not eat or drink) for several hours before the test. For accuracy, your blood sample is usually scheduled for three to four hours after you wake up. Tell your provider about any medicines or vitamins you take, as they can affect prolactin levels. Do not stop any medicine without talking to your provider first.
A health care professional will take a blood sample from a vein in your arm using a small needle. The process usually takes less than five minutes.
There is very little risk to having a blood test. You may have slight pain or bruising at the spot where the needle was put in, but most symptoms go away quickly.
Understanding results
Your provider will interpret your prolactin level based on your symptoms, sex, medical history, and other test results. The following patterns describe possible findings.
- Higher-than-normal prolactin level: May indicate a prolactinoma, another pituitary disorder, hypothalamus disease, hypothyroidism, cirrhosis, kidney disease, or polycystic ovary syndrome (PCOS) in women. Small increases can also be caused by high-protein diets, certain medicines, stress, exercise, or sex. Limitation: This test cannot show the cause of a high level. Further testing is needed to determine the underlying condition. Next step: Your provider will usually order other blood tests and may recommend an MRI to check for pituitary tumors. Treatment depends on the cause and is usually medicine; surgery may be needed for certain tumors.
- Lower-than-normal prolactin level: Rare, but may be a sign of a pituitary disorder. In women, it may cause difficulty producing enough milk for breastfeeding. Limitation: Low levels are uncommon and may not cause symptoms other than breastfeeding issues. Next step: Discuss with your provider to determine if further evaluation is needed.
- Higher-than-normal levels do not always mean a medical condition needs treatment; small increases can be temporary.
- The test cannot identify the specific cause of abnormal prolactin levels.
- Results must be interpreted alongside symptoms, medical history, and other tests.
What to do next
If your results are abnormal, your provider will discuss further testing and treatment options. For high levels, additional blood tests and possibly an MRI may be ordered. For low levels, your provider will advise on any necessary follow-up.
- What symptoms led to this test being ordered?
- Do I need any additional tests based on my prolactin level?
- Could any medicines or supplements I take affect my prolactin level?
- What does my result mean for my fertility or menstrual cycles?
- How often should I be retested if my levels are abnormal?