The Prolactin test is a simple blood test that measures the amount of prolactin (a hormone) circulating in your bloodstream. Prolactin is made mainly by the pituitary gland, a small gland at the base of the brain that helps regulate many body hormones. Prolactin plays an important role in reproductive health, especially breast development and milk production after pregnancy, and it also interacts with other hormones that control ovulation and menstrual cycles.

In plain language, your result shows whether prolactin is in a typical range for your situation (such as being pregnant, breastfeeding, or not pregnant). Higher-than-normal prolactin (hyperprolactinemia) can sometimes disrupt the balance of reproductive hormones. In women, this may contribute to irregular or missed periods and difficulty ovulating; in men, it may affect testosterone and sexual function. Lower-than-normal prolactin is less common and is usually only meaningful in specific clinical contexts (for example, suspected pituitary dysfunction).

Because prolactin levels can change with stress, sleep, exercise, nipple/breast stimulation, and certain medications, an abnormal result may lead your clinician to repeat the test and/or order related hormone tests to confirm a true hormonal imbalance or an underlying endocrine disorder.

Clinicians commonly order a prolactin blood test when symptoms suggest a hormone-related cause of reproductive or pituitary problems. It is frequently used in women’s health and fertility evaluations, but it can be helpful for all genders.

Your doctor may recommend prolactin testing if you have:

Menstrual and reproductive symptoms (often in women): missed periods (amenorrhea), irregular cycles, unexplained menstrual issues, trouble ovulating, or infertility. Elevated prolactin can suppress hormones needed for ovulation.

Unexpected breast milk production: milky nipple discharge when not pregnant or breastfeeding (galactorrhea). This can occur with elevated prolactin.

Symptoms related to pituitary gland conditions: headaches, vision changes (especially loss of peripheral vision), or other signs that may suggest a pituitary tumor such as a prolactin-secreting adenoma (prolactinoma).

Sex hormone-related symptoms (can affect any gender): decreased libido, erectile dysfunction, vaginal dryness, or low testosterone symptoms, which may be linked to endocrine disorders involving prolactin and other hormones.

Medication or health condition monitoring: some medicines (for example certain antipsychotics, antidepressants, anti-nausea drugs, opioids, and others) can raise prolactin. Doctors may check levels if symptoms occur or to evaluate side effects.

Prolactin is also sometimes checked alongside other tests that influence reproductive hormones—such as thyroid function (TSH), LH/FSH, estradiol, testosterone, and pregnancy testing—because thyroid problems and other hormonal conditions can contribute to abnormal prolactin levels and similar symptoms.

• Hyperprolactinemia (elevated prolactin)

• Prolactinoma (prolactin-secreting pituitary adenoma)

• Other pituitary gland tumors or pituitary disorders affecting hormone production

• Hypothyroidism (underactive thyroid), which can contribute to high prolactin

• Polycystic ovary syndrome (PCOS) (may be evaluated in the workup of menstrual irregularities)

• Hypogonadism (low sex hormone levels, including low testosterone in men or disrupted ovarian function)

• Endocrine disorders causing hormonal imbalance that affects fertility and menstrual cycles

• Identifying causes of infertility and supporting fertility planning

• Evaluating and managing menstrual issues (missed or irregular periods)

• Assessing hormonal imbalance and overall reproductive hormone health

• Supporting women’s health evaluations, including unexplained breast milk discharge

• Checking for pituitary gland problems when symptoms suggest an endocrine cause

• Monitoring treatment response for prolactinoma or other endocrine disorders (when applicable)

• Reviewing potential medication-related hormone side effects when symptoms arise