Prolactin Blood Test

What Is Prolactin?

Prolactin (pro-LAK-tin), or PRL, is a hormone made by the pituitary gland, which is a small gland in the brain. Prolactin’s main job is to help the body get ready to lactate (make breast milk) during pregnancy and keep up the milk supply during breastfeeding. Sometimes, prolactin levels rise even when someone isn’t pregnant or breastfeeding. 

What Is a Prolactin Test and Why Is It Done?

A prolactin test measures the amount of prolactin in the blood. 

Doctors may order the test:

• to help diagnose or monitor the treatment of prolactinoma —  a usually benign (not cancerous) tumor in the pituitary gland that makes extra prolactin
• as part of testing for conditions linked to changes in prolactin levels, like irregular periods, fertility problems, some thyroid or adrenal gland problems, anorexia, and polycystic ovary syndrome
• if someone’s taking medicine that makes the pituitary gland release more prolactin into the blood

Top Things to Know

• The prolactin test checks the level of a hormone called prolactin in the blood.
• The test helps doctors diagnose pituitary gland problems and other conditions.
• Kids might need to stop taking certain medicines or not eat or drink before the blood test.
• Your doctor can explain what it means if prolactin levels are too high or too low.

How Can I Help My Child Prepare for a Blood Test?

To help kids get ready for a prolactin test, find out if they need to fast (not eat or drink) or should stop taking medicines before the test. Tell your doctor about any medicines your child takes because some may increase levels of the hormone. The test might be done at a certain time of day when prolactin levels aren’t usually high (for instance, a few hours after your child wakes up). 

Explain what to expect during a blood test. If your child is nervous about it, work together on ways to stay calm. Deep breathing or even imagining being in a place that makes your child feel safe and relaxed can help.

What Do Prolactin Test Results Mean?

Your doctor will explain what the results of the test mean for your child. “Normal” prolactin levels vary based on things like age and gender. 

High Prolactin Levels

Prolactin levels change throughout the day and night — they're highest during sleep, just after waking up, following heavy exercise, and during periods of stress. Eating a meal that’s high in protein can raise levels for a short time as well.

A high prolactin level also could be due to things like:

• an injury or irritation to the chest area
• problems with the hypothalamus (a gland in the brain), pituitary gland, thyroid gland, or kidneys
• a condition where the body doesn’t get rid of prolactin in the blood the right way 
• certain medicines and marijuana products

Low Prolactin Levels

A problem with the pituitary gland could cause a low prolactin level. Some medicines can also lead to levels that are lower than usual.

What Else Should I Know?

Your child may need to have another prolactin test if the level is high or low. Your doctor may also recommend seeing an endocrinologist (a doctor who cares for diseases of the endocrine system, like problems with the thyroid).

If you have questions about the prolactin test or what the results mean, talk with your doctor.