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  • Also Known As:
  • PRL
  • PRL Test
  • Prolactin Blood Test
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Test Quick Guide

A prolactin test measures the amount of prolactin in the blood. Prolactin is a hormone produced by a pea-sized organ at the base of the brain called the pituitary gland.

Prolactin is often detected in high levels in people who are pregnant or just after childbirth. People who are not pregnant usually have low levels of prolactin in the blood.

A prolactin test may be ordered to help diagnose symptoms caused by prolactin levels that are too high or too low. Doctors may also order testing if they suspect a tumor in the pituitary gland called a prolactinoma.

About the Test

Purpose of the test

The purpose of a prolactin test is to measure the level of prolactin in the blood. The test can help a doctor diagnose certain health conditions and monitor patients with a type of pituitary tumor called a prolactinoma.

Diagnosis is testing to determine the cause of a patient’s symptoms. Doctors may order a prolactin test as part of the diagnostic process when a patient has symptoms that suggest a prolactin level that is higher or lower than normal.

Monitoring is observing a health condition or a person’s response to treatment over time. Doctors use prolactin testing to monitor patients who have a prolactinoma. Testing is performed during treatment to understand how well the treatment is working. Prolactin levels may also be tested periodically after treatment is finished to see if a prolactinoma has come back.

What does the test measure?

This test measures the amount of prolactin in a sample of blood. Prolactin is a hormone produced by the pituitary gland. It plays a role in breast development and the production of breast milk in women or anyone with ovaries. In men or anyone with testes, the normal function of prolactin is not known.

The pituitary gland is part of the body’s endocrine system, which is a group of organs and glands that make hormones. The hormones produced by the pituitary gland impact how many parts of the body function and regulate other components of the endocrine system.

In this way, abnormal levels of prolactin in the blood can alter the release of other hormones and cause a range of different health effects.

When should I get a prolactin test?

A prolactin test is usually ordered as part of the process of evaluating patients who have symptoms that could suggest an increase in prolactin levels. Elevated prolactin can interfere with the function of the ovaries and testes, which may cause the following symptoms:

  • Infertility
  • A change in sex drive
  • Breast milk production that is not related to pregnancy or childbirth
  • Erectile dysfunction
  • Irregular menstrual cycles

Postmenopausal patients who have vision changes or heachaches may also have testing to check for elevated prolactin levels and a possible prolactinoma that is pressing on nearby structures in the brain.

If you have been diagnosed with a prolactinoma, you may have your prolactin levels checked throughout treatment to monitor the effectiveness of treatment. After you complete treatment, your doctor may continue to measure your prolactin levels for a period of time to see if the tumor has come back.

You can speak with your doctor about whether a test to check your prolactin levels is appropriate. Your doctor can explain why they may order the test and what the results may mean for your health.

Finding a Prolactin Test

How to get tested

A prolactin test is most often ordered by a doctor. Testing is usually performed at a medical office, laboratory, or hospital.

Can I take the test at home?

At-home test kits are available to check prolactin levels. Test kits can be purchased online or at a local pharmacy. Inside the test kit you will find all of the materials needed to collect a blood sample using a finger prick and return the sample to the company for analysis. Results are usually available within a few days through a secure online platform.

While at-home test kits are convenient, this testing option should not replace working with your health care provider. If you have symptoms of high prolactin levels or have questions about the result of your at-home test, it is important to speak with a doctor.

How much does the test cost?

The cost of a prolactin test can depend on a number of factors including your health insurance status, where you have the test performed, and laboratory fees.

You can contact your health insurance provider if you have questions about the cost of testing. They will have information about whether it will be covered by your insurance plan and about any out-of-pocket costs such as copays and deductibles. If you do not have health insurance, you can ask the testing facility if they offer discounts or financial assistance.

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Taking a Prolactin Test

A test to measure prolactin levels is performed on a sample of blood. Usually, the sample is drawn from a patient’s arm in a doctor’s office, clinic, laboratory, or hospital.

Before the test

Generally, there is no special test preparation required before a prolactin test. For best accuracy the blood is drawn 3 to 4 hours after awakening in the morning.

However, in certain circumstances, patients may be asked to fast before having their prolactin levels measured. Fasting means you should not eat and should drink only water for 9 to 12 hours before testing.

Your doctor can provide you with information about any special test preparation that is needed before having your blood drawn.

During the test

A health professional will draw the blood sample needed for your prolactin test. The sample is usually drawn from a vein in the arm on the inside of the elbow.

The area will be cleaned with an antiseptic wipe, and an elastic band called a tourniquet will be placed around the upper part of the arm. The tourniquet helps to increase blood flow to the vein. Next, a needle will be inserted into the vein. You may feel slight discomfort when the needle is inserted. Blood will flow through the needle and will be collected in a test tube or vial attached to the needle. It should take no more than a few minutes to collect the sample needed for testing.

After the test

After the needle has been removed from the vein, pressure and a bandage will be applied to the area to stop the bleeding and to prevent bruising. Blood draws are a common medical procedure. There is little risk involved and you can usually resume your normal activities right away.

Prolactin Test Results

Receiving test results

The results of your prolactin test are usually reported to your doctor within a few business days. Your doctor may contact you directly to review your test results. They may also schedule an appointment to talk with you about your results and what they mean for your health.

You may receive a copy of your test results in the mail, or your results may be uploaded to your electronic medical record if you have access to an online health portal.

Interpreting test results

Prolactin blood test results are reported in nanograms per milliliter (ng/mL). The test report will include information about the reference range used to interpret your prolactin results. Reference ranges for prolactin are established by comparing prolactin levels among groups of healthy individuals based on their biological sex and pregnancy status. However, reference ranges can vary between laboratories, and there is no established normal prolactin level for all people.

Interpretation of prolactin test results can depend on several factors, including an individual’s health status and whether they have previously had prolactin testing. A doctor should always be consulted in order to understand prolactin test results in the appropriate medical context.

It is normal for people who are pregnant or nursing to have high levels of prolactin. Rarely, patients are diagnosed with a prolactin deficiency, known as hypoprolactinemia, which causes an inability to produce breast milk after birth.

In people who are not pregnant, an elevated prolactin found on an initial test may be a sign of hyperprolactinemia, which is the condition of having excess prolactin in the blood. However, because prolactin levels can be affected by certain foods, a repeat test is usually ordered after a period of fasting to confirm the diagnosis

Hyperprolactinemia can be caused by a wide range of conditions including kidney failure, thyroid problems, and diseases that affect brain regions like the hypothalamus or pituitary gland. A prolactin test cannot determine the underlying cause of high prolactin levels, so follow-up testing is usually necessary.

Elevated levels of prolactin can also be a sign of a prolactinoma, a benign tumor in the pituitary gland. Prolactinomas release high levels of prolactin into the blood. In general, larger tumors cause higher levels of prolactin. An imaging test, such as an MRI, is needed to confirm if a prolactinoma is present.

If a prolactinoma is diagnosed, effective treatment usually brings prolactin levels into a normal range. If post-treatment prolactin levels continue to be elevated and symptoms persist, doctors may make changes to the treatment plan. Periodic prolactin testing also occurs for several years after treatment is over to check for signs that the tumor has come back.

It is important to speak with your health care provider about the purpose of your prolactin test, how the results compare to the laboratory’s reference range, and what those results mean in your specific situation.

Are test results accurate?

Prolactin tests are a common laboratory test. While this test is widely regarded as accurate, no test is perfect.

Some factors can impact the results of a prolactin test including stress levels, strenuous exercise, breast exams, nipple stimulation, meals that are high in protein, and the use of some medications.

It is important to talk with your health care provider about any special test preparations to ensure an accurate result. You can also speak with your doctor if you have questions about the laboratory that performed your test or the reliability of your test results.

Do I need follow-up tests?

Elevated prolactin levels can be a sign of a variety of health conditions. If you have an abnormal level of prolactin in the blood, your doctor may suggest additional testing to identify the cause.

If you are experiencing symptoms of hyperprolactinemia, your doctor may begin by performing a physical exam and reviewing your medical history. They may also order an imaging test called a magnetic resonance imaging test (MRI) to rule out a prolactinoma.

Additional blood work may also be ordered to check thyroid and kidney function. Tests that may be ordered include:

Your health care provider can give you information about follow-up tests that are appropriate for your situation.

Questions for your doctor about test results

Your doctor can help address questions about prolactin testing and your test results. Some questions you may choose to ask your doctor include:

  • What do my test results say about my hormone function and my overall health?
  • Do I need follow-up tests based on the results of my prolactin test?
  • How often will I need prolactin testing if I am being treated for a prolactinoma?
  • How frequently will my prolactin levels be measured if I am being monitored for a recurrence of prolactinoma?

View Sources

A.D.A.M. Medical Encyclopedia. Prolactin blood test. Updated August 29, 2020. Accessed December 3, 2021. https://medlineplus.gov/ency/article/003718.htm

Carmichael JD. Overview of the pituitary gland. Merck Manuals Consumer Edition. Updated March 2021. Accessed December 3, 2021. https://www.merckmanuals.com/home/hormonal-and-metabolic-disorders/pituitary-gland-disorders/overview-of-the-pituitary-gland

Gremida AK. Prolactin. In: Wheeler TM, ed. Medscape. Updated November 22, 2019. Accessed December 6, 2021. https://emedicine.medscape.com/article/2089400-overview

MedlinePlus: National Library of Medicine. Prolactin levels. Updated December 17, 2020. Accessed December 6, 2021. https://medlineplus.gov/lab-tests/prolactin-levels/

Morley JE. Endocrine glands. Merck Manuals Consumer Edition. Updated April 2019. Accessed December 3, 2021. https://www.merckmanuals.com/home/hormonal-and-metabolic-disorders/biology-of-the-endocrine-system/endocrine-glands

National Cancer Institute. Dictionary of cancer terms: Gland. Date unknown. Accessed November 15, 2021. https://www.cancer.gov/publications/dictionaries/cancer-terms/def/gland

PDQ Adult Treatment Editorial Board. PDQ pituitary tumors treatment (adult): Patient version. National Cancer Institute. Updated September 24, 2020. Accessed December 6, 2021. https://www.cancer.gov/types/pituitary/patient/pituitary-treatment-pdq

Snyder PJ. Clinical manifestations and evaluation of hyperprolactinemia. In: Cooper DS, ed. UpToDate. Updated March 23, 2020. Accessed December 7, 2021. https://www.uptodate.com/contents/clinical-manifestations-and-evaluation-of-hyperprolactinemia

Snyder PJ. Management of hyperprolactinemia. In: Cooper DS, ed. UpToDate. Updated July 20, 2020. Accessed December 6, 2021. https://www.uptodate.com/contents/management-of-hyperprolactinemia

Snyder PJ. Patient education: High prolactin levels and prolactinomas (beyond the basics). In: Cooper DS, ed. UpToDate. Updated May 9, 2020. Accessed December 6, 2021. https://www.uptodate.com/contents/high-prolactin-levels-and-prolactinomas-beyond-the-basics

Snyder PJ. Lab interpretation: High prolactin in adults. In: Cooper DS, ed. UpToDate. Updated May 11, 2021. Accessed December 8, 2021. https://www.uptodate.com/contents/high-prolactin-in-adults

Snyder PJ. Causes of hyperprolactinemia. In: Cooper DS, ed. UpToDate. Updated October 29, 2021. Accessed December 7, 2021. https://www.uptodate.com/contents/causes-of-hyperprolactinemia

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