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Prolactin Levels
Reviewed by Medicinsk Expert•Last updated: 2026-10-22•Lab Tests

Prolactin Levels

A prolactin test measures the level of the hormone prolactin in your blood to help diagnose conditions like pituitary tumors, infertility, and menstrual irregularities.

What is a prolactin test?

A prolactin (PRL) test measures the level of prolactin in a sample of your blood. Prolactin is a hormone produced by the pituitary gland, a small gland at the base of the brain. Hormones are chemical messengers in your bloodstream that control the actions of certain cells or organs.

Prolactin affects many body processes, but its main role is to signal breast tissue to grow during pregnancy and make milk for breastfeeding after birth. Consequently, prolactin levels in pregnant women and new mothers are normally high, while levels in nonpregnant women and men are normally low.

Having higher-than-normal prolactin levels, known as hyperprolactinemia, can affect the body in several ways:

  • In women: It can affect how the ovaries work and cause menstrual problems and infertility.
  • In men: It can affect how the testicles work and cause a lower sex drive and erectile dysfunction (ED).
  • In non-nursing individuals: It can signal the body to start producing breast milk.

Causes of High Prolactin Levels

Higher-than-normal levels can be caused by various factors:

  • Prolactinoma: A benign (noncancerous) tumor on the pituitary gland, which is the most common cause.
  • Certain medicines.
  • Health conditions: Such as hypothyroidism (underactive thyroid), kidney disease, and chest injuries.
  • Other pituitary gland tumors.

What is it used for?

A prolactin test is typically used to:

  • Diagnose a prolactinoma.
  • Identify the cause of irregular menstrual periods or infertility.
  • Determine the cause of low sex drive or erectile dysfunction in men.
  • Monitor a known prolactinoma to see if treatment is working or if the tumor has returned.

Symptoms

Symptoms of high prolactin levels vary by sex:

In Women

  • Changes in menstruation (irregular or absent periods)
  • Production of breast milk when not pregnant or breastfeeding
  • Nipple discharge
  • Infertility

In Men

  • Nipple discharge
  • Erectile dysfunction/impotence
  • Enlarged breasts (gynecomastia)
  • Decreased facial and body hair
  • Low sex drive

If a prolactinoma is present, it may also cause headaches, vision changes (if pressing on the optic nerve), or low levels of other pituitary hormones.

Test Procedure and Preparation

A health care professional will collect a blood sample from a vein in your arm. The process usually takes less than five minutes.

Your provider may ask you to fast for several hours before the test. Because prolactin levels fluctuate throughout the day, blood samples are typically scheduled three to four hours after you wake up. Be sure to inform your provider about any medicines or vitamins you are taking, but do not stop taking them without consulting your provider first.

Understanding Results

Your provider will interpret your results based on your symptoms, sex, and medical history. Higher-than-normal levels may indicate a pituitary disorder, hypothalamus disease, hypothyroidism, cirrhosis, kidney disease, or polycystic ovary syndrome (PCOS). Small increases can also be caused by stress, exercise, or sexual activity.

Lower-than-normal levels are rare but may indicate a pituitary disorder, which can result in an inability to produce enough milk for breastfeeding.

Frequently Asked Questions

Common causes include dopamine‑blocking drugs (e.g., antipsychotics, certain blood pressure meds), hypothyroidism, chronic kidney disease, and chest trauma. Even stress or excessive exercise can transiently raise prolactin, though these effects are usually mild.
fter initiating therapy, levels are typically checked 4–6 weeks later to assess response. If stable, follow‑up every 3–6 months is common, with more frequent checks if symptoms persist or if dose adjustments are needed.===
The first line is usually a dopamine agonist such as cabergoline or bromocriptine, which shrinks prolactin‑secreting tumors and normalizes hormone levels. If medication fails or is contraindicated, surgical removal of the pituitary tumor or radiation therapy may be considered.
void strenuous exercise, alcohol, and caffeine for 24 hours before the test. If you are on medications that affect prolactin, discuss with your provider whether to pause or adjust them. Fasting is not required, but it is best to keep your routine consistent on the day of the draw.
Source: MedlinePlus, National Library of Medicine

MedlinePlus brings together authoritative health information from the National Library of Medicine (NLM), the National Institutes of Health (NIH), and other government agencies and health-related organizations.

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