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Prolactin Blood Test: Normal Range + High & Low Levels

Written by Aleksa Ristic, MS (Pharmacy) | Reviewed by Ana Aleksic, MSc (Pharmacy) | Last updated:
Medically reviewed by
Ognjen Milicevic, MD, PhD (Bioinformatics), Puya Yazdi, MD | Written by Aleksa Ristic, MS (Pharmacy) | Reviewed by Ana Aleksic, MSc (Pharmacy) | Last updated:

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Prolactin blood test

You may know prolactin as the lactation hormone, but this lab marker can reveal a lot about your health – men included! In this article, we’ll dive into details about the prolactin blood test and discuss natural solutions to improve reproductive health. Read on!

What is Prolactin?

Prolactin (PRL) is a pituitary hormone that stimulates breast milk production in women after childbirth. It also supports the immune system, mental health, and metabolism in both sexes. To learn more about its roles and factors that control its secretion, read the first part of this series.

Prolactin Blood Test

When is It Ordered?

Pregnant and breastfeeding women will normally have high prolactin levels.

Abnormal levels in nonpregnant women and men can cause different signs and symptoms, including abnormal nipple discharge and fertility issues. In women, it can result in irregular or missing periods. In men, it can lead to erectile dysfunction or reduced libido [1].

A doctor may order the test to find out if high or low prolactin is triggering the symptoms. The test may also screen for pituitary tumors and medical conditions with impaired dopamine signaling.

Prolactin can be a part of routine sex hormones workup, along with:

How to Prepare for the Test

Experts suggest doing a prolactin blood test 3-4 hours after waking up. Avoid breast stimulation, sexual intercourse, physical exams, and stress the day before and that morning. This also means that you shouldn’t have a breast exam right before the blood draw, a mistake that sometimes happens in busy doctors’ offices [2, 3, 4].

Your doctor may suggest taking another blood sample in 30 mins to minimize the effects of stress and other external factors [5, 6].

In case of abnormal results, you may need to repeat the test to get the most accurate readings [2, 3].

Normal Levels

Normal prolactin blood levels vary between sexes: they range between 4-23 ng/mL (mcg/L) in adult nonpregnant women and 3-15 ng/mL in men [7, 3].

Men3-15 ng/mL (mcg/L)
Nonpregnant women4-23 ng/mL (mcg/L)
Pregnant women34-386 ng/mL (mcg/L)
Children3.2-20 ng/mL (mcg/L)

In women, prolactin slightly varies depending on the phase of the menstrual cycle. During pregnancy, levels increase and can reach up to 20x the normal values before childbirth [8].

On the other hand, prolactin levels remain constant in healthy men and slightly drop with aging. They may peak in response to stress and other factors discussed below [9].

High Prolactin Levels

Prolactin levels are a marker of reproductive health. Low or high levels don’t necessarily indicate a problem if there are no symptoms or if your doctor tells you not to worry about it.

Causes

High blood prolactin (>25 ng/mL) or hyperprolactinemia mostly affects young women (25-34 years). It can be a normal occurrence due to [10, 11]:

  • Pregnancy
  • Breastfeeding
  • Breast and nipple stimulation
  • Stress

Medications, pituitary tumors, and other diseases can cause abnormal hyperprolactinemia, which may require medical attention [3].

1) Pregnancy and Breastfeeding

Prolactin levels rise during pregnancy in response to estrogen stimulation, and they can get 10-20 times higher than usual (up to 500 ng/mL) [8, 12].

After childbirth, high prolactin enables women to make breast milk [13].

Once the nursing begins, suckling becomes the primary stimulus for prolactin secretion and maintains milk production; nipple and breast stimulation cause prolactin spikes during breastfeeding. Elevated prolactin also prevents ovulation and new pregnancies shortly after childbirth [14, 15, 16].

2) Stress

Our brain releases prolactin (PRL) in response to stress, and it’s a common cause of high prolactin, especially in men [17].

If you feel stressed during blood sampling, you PRL levels can transiently rise. This is known as stress-related hyperprolactinemia. To avoid it, doctors suggest taking multiple samples in complete rest [5].

3) Pituitary Tumors

Prolactinomas are prolactin-secreting tumors of the pituitary gland. Based on the tumor size, the two most common types are microprolactinoma (<10 mm) and macroprolactinoma (> 10 mm). Doctors still don’t know the exact cause of these benign tumors [18].

Expected blood prolactin levels in prolactinoma are over 250 ng/mL. A person may also experience headaches and vision problems if the tumor is pressing on certain brain areas. A doctor will suggest a CT or MRI scan to confirm or exclude this condition [3].

Most prolactinomas respond well to drugs that block prolactin secretion and don’t require chemotherapy or radiation. They are the most common disease-related cause of elevated PRL and usually affect younger women [19, 20].

4) Underactive Thyroid

Thyroid hormones normally work in a negative feedback loop that starts in the brain: TRH (from your hypothalamus) increases TSH and prolactin. TSH, in turn, increases thyroid hormones. To avoid their own excess, thyroid hormones will block TRH once they reach normal levels [21].

When the thyroid is underactive, thyroid hormones aren’t high enough to block TRH, leading to high prolactin levels [22, 23].

At the same time, hypothyroidism prevents the body from getting rid of prolactin [21].

5) Macroprolactinemia

In macroprolactinemia, anti-PRL antibodies bind prolactin molecules and create big protein complexes called “large prolactin.” This massively increases PRL blood levels (over 500 ng/mL) [24, 25].

About 10-25% of people with elevated prolactin have macroprolactinemia; most of them are symptom-free and don’t require medical treatment [26].

6) Medications

Some drugs can increase prolactin (usually up to 100 ng/mL) by suppressing its primary inhibitor, dopamine. This side effect is most common for antipsychotics such as [27, 28]:

  • Haloperidol (Haldol)
  • Chlorpromazine (Largactil, Thorazine)
  • Thioridazine (Mellaril or Melleril)
  • Risperidone (Risperdal)

Antipsychotics reduce dopamine activity in the brain (by blocking D2 receptors) [29].

The following drugs may also raise prolactin levels [30, 31, 32]:

  • Estrogens (including birth control)
  • Anti-androgens (cyproterone acetate/Diane)
  • Nausea medications (metoclopramide)
  • Antidepressants
  • Blood pressure drugs (methyldopa, reserpine, and verapamil)
  • Drugs for acid reflux (cimetidine and ranitidine)

If doctors suspect drug-induced hyperprolactinemia, they will suggest a medication replacement that won’t impact prolactin secretion.

7) Other

The following conditions may also cause high prolactin:

Signs and Symptoms

If you have high prolactin, your doctor will discuss the results with you. They may run additional tests to pinpoint the underlying cause of your high levels.

Elevated prolactin (hyperprolactinemia) can reduce fertility and libido in both sexes while abnormal breast milk flow (galactorrhea) is much more common in women [11, 40].

High levels of prolactin in women may also cause [3, 22]:

  • Irregular cycles
  • Vaginal dryness
  • Fatigue
  • Acne
  • Headaches

Additional signs and symptoms in men include [11, 40, 41]:

  • Erectile dysfunction
  • Bone and muscle loss
  • Reduced beard growth

Most symptoms in both sexes stem from suppressed sex hormones, a result of prolactin blocking GnRH.

Associated Conditions & Health Effects

1) Reduced Fertility

High prolactin during breastfeeding causes a transient drop in fertility, which protects the mother from a new pregnancy [11, 42].

In women trying to conceive, high prolactin levels prevent ovulation, lower sex hormones, and reduce the chance of pregnancy. Prolactin-lowering treatment significantly increased estradiol in 32 infertile women [43, 44].

During pregnancy, abnormally high prolactin levels may increase the risk of spontaneous miscarriages. In 352 pregnant women with this issue, a prolactin-lowering drug increased the chance of a successful pregnancy by 33%; women who miscarried had significantly higher PRL. A smaller study failed to confirm this connection [45, 46].

2) Weight Gain

Prolactin increases appetite and food intake by causing leptin resistance. This effect is meant to provide extra energy and nutrients during pregnancy, but it can happen in all conditions with high prolactin [47, 48, 49, 50].

Increased insulin secretion and glucose sensitivity due to high prolactin may contribute to weight gain [9, 51, 52, 53].

Obesity correlated with high prolactin in 78 people with prolactin-secreting tumors or prolactinomas. As soon as their prolactin levels normalized, 70% managed to lose weight [54].

A smaller study observed that many people with prolactinomas are obese. This time, however, the reduction in prolactin levels didn’t impact weight loss [51].

3) Autoimmune Diseases

Optimal prolactin levels boost your immune system. In hyperprolactinemia, this effect is exaggerated and may play a role in different autoimmune diseases such as [55, 56, 57, 58]:

In some cases, prolactin-lowering drugs can improve the symptoms and stop disease progression [58, 59].

People with lupus frequently have high prolactin levels. The more their prolactin levels rise, the more severe symptoms they experience. The connection is particularly strong in pregnant women [60, 59, 61].

The female-dominant role of prolactin might also explain why women are more likely to suffer from autoimmune diseases [62].

4) Mood Swings and Behavior

Normal levels of prolactin combat stress and support mental health, especially during and after pregnancy. However, excess levels can cause mood swings and worsen mental disorders [63, 64, 65].

According to a review of clinical trials, high prolactin (PRL) may increase the risk of anxiety and depression in both men and women. Lowering high PRL levels significantly improved the symptoms in some patients [66].

In 25 depressed patients, some symptoms – such as feelings of detachment – correlated with prolactin levels. However, two studies of 160 patients found no connection between this hormone and depression [67, 68, 69].

Molecules made by breaking prolactin into smaller bits (called vasoinhibins – more about them below) triggered anxiety and depression in rats [70].

High prolactin can make women hostile, probably as a means to protect their children at all costs. It doesn’t seem to have the same effect on men [71].

In summary, high prolactin may disrupt mood and behavior, but the research is too limited to draw a conclusion.

5) Breast Cancer

According to an observational trial with over 6,000 women, high prolactin levels correlate with up to 50% increased rates of breast cancer. The connection was strongest for postmenopausal women with estrogen receptor-positive (ER+) and metastatic tumors [72].

Two studies on 2,000 women came to the same conclusion and found 30-60% increased rates for the highest vs. lowest prolactin values (>17.6 ng/mL vs. <9.8 ng/mL) [73, 74].

6) Bone Loss

After childbirth, high prolactin increases PTH to free calcium from the bones, making it available for breast milk production. In cases of chronic hyperprolactinemia, this may lead to bone loss and increase the risk of fractures in both sexes [75, 76, 77].

7) Migraines

According to two smaller clinical trials (56 patients), high prolactin (150 ng/mL) may be associated with migraine attacks. Prolactin-lowering treatment improved the symptoms and reduced migraine frequency in some patients [78, 79].

8) Blood Pressure and Heart Disease

Our body cuts prolactin molecules into vasoinhibins, smaller peptides that reduce the growth and leakiness of blood vessels [80].

Hyperprolactinemia and oxidative stress increase vasoinhibins, impair blood vessel growth, and raise the risk of heart disease after pregnancy. Drugs that lower prolactin showed promising results in animals with this condition [81, 82].

According to a study on mice, excess vasoinhibins may also increase blood pressure by blocking the production of nitric oxide [83].

However, some researchers have emphasized that vasoinhibins don’t always correlate with blood prolactin and suggested monitoring their levels directly [84].

9) Other

An observational study of over 7,000 subjects investigated the impact of hyperprolactinemia on overall mortality. Researchers found a link between death rates and high prolactin (>47 ng/mL) caused by [85]:

  • Hypothyroidism
  • Larger prolactin-secreting tumors (macroprolactinomas)
  • Drugs

However, they pointed out that high prolactin has no direct effect on someone’s chance of dying. Instead, the underlying disease likely has an impact.

Patients with drug-induced hyperprolactinemia also had higher rates of:

  • Diabetes
  • Heart disease
  • Infections
  • Bone fractures

High Prolactin? Ways to Support Reproductive Health

Prolactin levels are a marker of reproductive health. High levels don’t necessarily indicate a problem if there are no symptoms or if your doctor tells you not to worry about it. Addressing your prolactin levels won’t necessarily cause improvement in reproductive health.

The following is a list of treatment options and complementary approaches to improve reproductive health that may also balance high prolactin. Though studies suggest various dietary and lifestyle factors may lower prolactin, additional large-scale clinical trials are needed.

Remember to talk to your doctor before making any major changes to your day-to-day routine.

Drug Treatment

Some cases of hyperprolactinemia require drug treatment. Since dopamine is the main blocker of prolactin, a doctor may prescribe a dopamine agonist such as bromocriptine or cabergoline [86, 87].

These drugs may help with abnormal nipple discharge, autoimmune diseases, migraines, infertility, and other conditions caused by elevated prolactin [88, 89, 45, 79].

Complementary Approaches

Supplements that may boost fertility and libido (as measured by lowering prolactin) include:

Low Prolactin Levels

Prolactin levels are a marker of reproductive health. Low or high levels don’t necessarily indicate a problem if there are no symptoms or if your doctor tells you not to worry about it.

Abnormally low prolactin levels (hypoprolactinemia) are rare and usually don’t require medical attention [101].

Causes

1) Drugs

Dopamine agonists mentioned above may cause hypoprolactinemia, along with ergot alkaloids and atypical antipsychotics (aripiprazole) [102, 103].

2) Pituitary Disorders

Underactive pituitary gland (hypopituitarism) is another common cause of low prolactin [101].

Primary hypopituitarism is a rare condition with decreased production of prolactin, growth hormone and sex hormones. It delays growth and sexual development in children and causes premature aging in adults [104, 105].

Sheehan syndrome is another pituitary disorder that drops prolactin. It may occur due to massive blood loss during childbirth, which cuts the blood supply to the pituitary gland [106].

3) Other

Obesity in pregnant women can lower prolactin levels and impair lactation [107, 108].

Although prolactin secretion peaks during sleep, abnormal melatonin levels (from daily exposure) may reduce it [109].

Signs and Symptoms

If you have low prolactin, your doctor will discuss the results with you. They may run additional tests to pinpoint the underlying cause of your low levels.

The primary symptom of low prolactin after childbirth is insufficient milk production. In non-pregnant women, it can cause ovary dysfunction and irregular/absent cycles [110, 111].

The lack of prolactin in new moms can also trigger anxiety and raise their risk of diabetes [63, 112].

In men, hypo- and hyperprolactinemia have similar symptoms such as [113, 114, 115]:

  • Erectile dysfunction
  • Reduced libido
  • Infertility
  • Premature ejaculation
  • Metabolic syndrome

Low prolactin levels may also suppress your immune system [116].

Low Prolactin? Natural Ways to Stimulate Milk Production

Women with inadequate lactation often seek natural ways to boost prolactin. Supplements that can stimulate milk production (galactagogues) include:

High levels of oxytocin after childbirth are also essential to increase prolactin and stimulate milk ejection. The following factors support lactation by increasing mother’s oxytocin [122, 123]:

  • Intimate contact with her baby
  • Hearing the baby cry for food
  • Loving thoughts about the baby
  • Support and comfort from her environment

The following activities may boost prolactin levels, but the clinical significance of this effect is not clear [3, 124, 125, 126, 127, 128]:

In rare cases, abnormally low prolactin may have more serious consequences such as infertility and thus require medical attention.

Take-Away

Stress, pituitary tumors, low thyroid hormones, and schizophrenia treatment can excessively raise prolactin levels. Accompanying signs and symptoms include nipple discharge, low libido, infertility, irregular cycles, weight gain, mood swings, and migraines.

Supplements that may boost fertility and libido (as measured by lowering prolactin) include chaste tree, mucuna, ginseng, ashwagandha, and zinc). Getting more dietary protein and healthy fats might also help, but the available evidence is weak.

High prolactin levels (>25 ng/mL) normally occur during pregnancy and breastfeeding. Women with low prolactin after childbirth don’t produce enough breast milk. Herbal supplements (fennel, fenugreek, silymarin, moringa), a supportive environment, and intimate mother-baby contact can increase milk production.

Low prolactin levels may also be due to certain medications or pituitary disorders, which can lead to sexual dysfunction and poor immunity. If you have low or high levels, make sure to discuss the results with your doctor.

About the Author

Aleksa Ristic

MS (Pharmacy)
Aleksa received his MS in Pharmacy from the University of Belgrade, his master thesis focusing on protein sources in plant-based diets. 
Aleksa is passionate about herbal pharmacy, nutrition, and functional medicine. He found a way to merge his two biggest passions—writing and health—and use them for noble purposes. His mission is to bridge the gap between science and everyday life, helping readers improve their health and feel better.

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