What Is a Prolactin Test?

Medically Reviewed by Jabeen Begum, MD on December 14, 2023
6 min read

A prolactin (PRL) blood test measures how much of a hormone called prolactin you have in your blood. The hormone is made in your pituitary gland, which is located just below your brain.

When people are pregnant or have just given birth, their prolactin levels increase so they can make breast milk. But it’s possible to have high prolactin levels if you’re not pregnant. Anyone can have high prolactin levels.

Prolactin helps your body work properly. It supports many actions and processes that happen in the body every day, including the creation of blood vessels.

Prolactin is especially important for pregnant people. It makes lactation and milk production possible.

People assigned male at birth have lower levels of prolactin.

How is it made?

Many hormones, including prolactin, come from the pituitary gland. Dopamine, a neurotransmitter, and estrogen, a hormone, signal to the pituitary gland that it’s time to produce and distribute prolactin. 

Other areas of the body that create prolactin include the mammary glands, uterus, immune system, and even the central nervous system.

How it works in the body

Prolactin encourages mammary glands in the breast to grow and develop. It nurtures breast tissue in the mammary glands called “mammary alveoli,” where milk is produced. Combined with estrogen and progesterone, prolactin prompts the breasts to create milk.

Prolactin also helps ensure the breast milk contains all the necessary nutrition for a baby, including lipids for energy, casein for protein, and lactose for carbohydrates.

Prolactin helps maintain the milk supply for feeding an infant. It rises when the baby feeds at the breast. If you deliver a baby but decide not to breastfeed, your prolactin will typically fall within 2 weeks to its level before your pregnancy.

Why would your prolactin level rise?

Your prolactin level may change throughout the day. Many common activities such as eating a meal or exercising can affect prolactin levels. So can:

  • Sex

  • Nipple stimulation

  • Physical stress

  • Injuries

  • Seizures

The normal range for prolactin in your blood is:

  • Male/assigned male at birth: less than 20 nanograms per milliliter (ng/mL)

  • Non-pregnant female/assigned female at birth: less than 25 ng/mL

  • Pregnant people: 80 to 400 ng/mL

What’s considered normal may be different depending on which lab your doctor uses.

If your value falls outside the normal range, this doesn’t automatically mean you have a problem. Sometimes the levels can be higher if you’ve eaten or were under a lot of stress when you got your blood test.

High levels of prolactin, also known as hyperprolactinemia, can cause infertility in women. Periods can become irregular.

If your levels are very high -- up to 1,000 times the upper limit of what’s considered normal -- this could be a sign that you have prolactinoma -- a tumor in your pituitary gland. This tumor is not cancer, and it is usually treated with medicine. In this case, your doctor may want you to get an MRI, which uses radio waves to put together a detailed image of your brain. It will show whether there’s a mass near your pituitary gland and how big it is.

Normally, men and nonpregnant women have just traces of prolactin in their blood. When you have high levels, this could be caused by:

  • Prolactinoma (a benign tumor in your pituitary gland that produces too much prolactin)
  • Diseases affecting the hypothalamus (the part of the brain that controls the pituitary gland)
  • Anorexia (an eating disorder)
  • Drugs that are used to treat depression, psychosis, high blood pressure, nausea, and vomiting, pain relievers with opioids, and birth control pills
  • Chest injury or irritation (for example, scars, shingles, or even a bra that’s too tight)

Certain health conditions, including kidney disease, hypothyroidism (an underactive thyroid), or shingles can also cause high prolactin levels. Shingles is more likely to trigger higher prolactin levels if it's on your chest. 

Also, kidney disease, liver failure, and polycystic ovarian syndrome (a hormone imbalance that affects ovaries) can affect the body’s ability to remove prolactin.

Your doctor may order a prolactin test when you report having the following symptoms:

For those assigned female at birth

  • Irregular or no periods
  • Bone loss
  • Infertility
  • Breast milk discharge when you’re not pregnant or nursing
  • Tenderness in your breast
  • Menopausal symptoms such as hot flashes and vaginal dryness

For those assigned male at birth

  • Decreased sex drive
  • Difficulty in getting an erection
  • Breast tenderness or enlargement
  • Breast milk production (very rare)

For anyone

  • Unexplained headaches
  • Vision problems

If your prolactin levels are below the normal range, this could mean your pituitary gland isn’t making one or more of the hormones it normally does, sometimes due to an injury to the gland. That’s known as hypopituitarism. Lower levels of prolactin usually do not need medical treatment.

One study found that a prolactin level of less than 5 ng/mL in women of reproductive age may increase a woman’s risk of metabolic syndrome. Metabolic syndrome is a group of medical conditions, including high blood pressure and high blood triglycerides, that collectively increase your risk of heart disease, stroke, and diabetes.

 For people who are pregnant or have recently given birth, a prolactin level under 80 ng/mL can limit their ability to breastfeed. Because your prolactin levels are typically low when you're breastfeeding (or chestfeeding), a lack of breast milk after delivering your baby is one of the only symptoms of low prolactin levels.

Also, certain drugs can cause low levels of prolactin. They include:

  • Dopamine (Intropin), which is given to people in shock
  • Levodopa (for Parkinson’s disease)
  • Ergot alkaloid derivatives (for severe headaches)

Your doctor may recommend certain medications to help with low prolactin levels, however treatment in these cases is not usually needed.

If you're having symptoms of high prolactin levels, your doctor may ask you to have testing. 

They may ask you to fast prior to this test to help ensure an accurate reading. 

You will get a blood sample taken at a lab or a hospital. A lab worker will insert a needle into a vein in your arm to take out a small amount of blood.

Some people feel just a little sting. Others might feel moderate pain and see slight bruising afterward.

After a few days, you’ll get the results of your prolactin test in the form of a number.



Your treatment will depend on the diagnosis. If it turns out to be a small prolactinoma or a cause can’t be found, your doctor may recommend no treatment at all.

In some cases, your doctor may prescribe medicine to lower prolactin levels. If you have a prolactinoma, the goal is to use medicine to reduce the size of the tumor and lower the amount of prolactin.

There are a few steps you can take to help lower your prolactin levels:

  • Look for ways to reduce stress, such as meditation.

  • Don't wear clothing that fits very tightly across your chest. 

  • Your doctor may recommend high-dose vitamin B6. Vitamin E has also lowered prolactin in some patients.

Though often associated with lactation and breastfeeding, prolactin is found in both men/those assigned male at birth and women/those assigned female at birth and supports the body in a variety of ways.

Prolactin levels can fluctuate throughout the day. Low or high levels of prolactin may require no medical treatment. Medication can be beneficial for patients living with infertility, sexual issues, or bone loss.

  • What is prolactin test for? The prolactin test measures how much of the prolactin hormone you have in your blood.

  • When should prolactin levels be checked? Women may need a prolactin test if they are experiencing irregular or no periods prior to menopause or infertility. Other reasons your doctor may suggest the test include bone loss or menopausal symptoms such as vaginal dryness.

Men who have decreased sex drive, difficulty getting an erection, or breast tenderness or enlargement may need a prolactin test.

  • What are the symptoms of high prolactin levels in females? Symptoms include breast tenderness or a discharge in the breast when you aren’t pregnant or nursing. Women with a high level of prolactin may have hot flashes or bone loss.

  • What happens if prolactin is high? A high level of prolactin can lead to infertility. A level up to 1,000 times the upper limit of what’s considered normal could be a sign that you have a noncancerous tumor called a prolactinoma. It is usually treated with medication.