Prolactin Levels Test

A prolactin test measures the level of prolactin in your blood. Prolactin is a hormone that helps with breast growth and milk production. High levels can affect fertility and sex drive, while low levels are rare but may affect breastfeeding.

What this test measures

A prolactin (PRL) test measures the level of prolactin in a sample of your blood. Prolactin is a hormone produced by the pituitary gland that signals breast tissue to grow during pregnancy and make milk for breastfeeding.

What your results mean

Reference ranges vary by laboratory and by your age and sex. MedlinePlus does not publish a single normal range for this test — always read your result against the range printed on your own lab report and discuss it with your provider.

Higher-than-normal results

Higher-than-normal prolactin levels may be a sign of prolactinoma, other pituitary disorders, hypothalamus disease, hypothyroidism, cirrhosis, kidney disease, or PCOS in women. Certain medicines, high-protein diets, stress, exercise, and sex can also cause high levels.

Lower-than-normal results

Lower-than-normal prolactin levels are rare but may be a sign of a pituitary disorder. Without enough prolactin, a woman may not make enough milk to breastfeed after birth.

Frequently asked questions

What is a prolactin test used for?

It is used to diagnose a prolactinoma, find the cause of irregular menstrual periods or infertility, find the cause of low sex drive or erectile dysfunction in men, and monitor treatment for a known prolactinoma.

What does high prolactin mean in women?

In women, high prolactin can affect how the ovaries work and cause menstrual problems and infertility.

What does high prolactin mean in men?

In men, high prolactin can affect how the testicles work and cause a lower sex drive and erectile dysfunction.

Can high prolactin levels be caused by stress?

Yes, small increases in prolactin may be caused by stress, exercise, and even having sex.

What happens if prolactin is low?

Low prolactin is rare but may be a sign of a pituitary disorder. In women, it can cause not enough milk to breastfeed after birth.

Sources

MedlinePlus: Prolactin Levels — NIH MedlinePlus

Last updated July 7, 2026. Information is aggregated from official public sources and is not a substitute for professional medical care.