Prolactin
Also known as: PRL
What Does Prolactin Measure?
Prolactin (PRL) is a hormone produced by the pituitary gland, a small gland located at the base of the brain. A prolactin blood test measures the level of this hormone circulating in your bloodstream, typically reported in nanograms per milliliter (ng/mL) or milli-international units per liter (mIU/L). Prolactin plays a central role in stimulating breast milk production after childbirth and is naturally elevated during pregnancy and breastfeeding.
Why Does Prolactin Matter?
Abnormal prolactin levels can signal important underlying health conditions. Elevated prolactin (hyperprolactinemia) can disrupt reproductive hormones in both men and women, leading to fertility problems, irregular menstrual cycles, reduced libido, and bone density loss. In some cases, high prolactin may indicate a pituitary tumor called a prolactinoma. Low prolactin levels are less commonly discussed but can indicate pituitary insufficiency. Because prolactin interacts closely with estrogen, testosterone, and other reproductive hormones, it is a key marker evaluated when investigating infertility, hormonal imbalances, or unexplained symptoms such as galactorrhea (unexpected milk production).
Normal Ranges
Males
2–18 ng/mL (42–375 mIU/L)
Females
Non-pregnant: 2–29 ng/mL (42–600 mIU/L); Pregnant: 10–209 ng/mL; Breastfeeding: up to 300 ng/mL
Children
Varies by age and sex; typically 3–20 ng/mL in prepubertal children
Causes of High Levels
- Prolactinoma (a benign pituitary tumor that secretes prolactin)
- Pregnancy and breastfeeding (physiologically normal elevation)
- Certain medications such as antipsychotics, antidepressants, antihypertensives (e.g., metoclopramide, risperidone, verapamil)
- Hypothyroidism (low thyroid hormone stimulates prolactin release via elevated TRH)
- Polycystic ovary syndrome (PCOS) in some cases
- Stress, physical exercise, or nipple stimulation shortly before blood draw
Causes of Low Levels
- Hypopituitarism (underactive pituitary gland producing insufficient hormones)
- Sheehan's syndrome (pituitary damage caused by severe postpartum hemorrhage)
- Dopamine agonist medications used to treat Parkinson's disease or prolactinomas
How to Improve Your Prolactin
Diet
- Reduce refined carbohydrates and sugars to support insulin sensitivity and hormone balance
- Include zinc-rich foods such as oysters, pumpkin seeds, and beef, as zinc helps regulate pituitary hormone secretion
- Consume adequate iodine and selenium through foods like seafood, eggs, and Brazil nuts to support thyroid function, which influences prolactin
- Eat foods rich in vitamin B6 (pyridoxine) such as chickpeas, salmon, and bananas, which may help modulate prolactin levels
- Limit alcohol consumption, as alcohol can interfere with pituitary hormone regulation
Supplements
- Vitamin B6 (pyridoxine): 50–100 mg/day has been studied for modestly reducing elevated prolactin levels
- Zinc: 15–30 mg/day to support pituitary and reproductive hormone function
- Vitex agnus-castus (chasteberry): 20–40 mg/day of standardized extract; some evidence supports mild prolactin-lowering effects
- Vitamin D: 1,000–2,000 IU/day to support overall hormonal health, particularly if deficient
- Ashwagandha: 300–600 mg/day of root extract to help reduce stress-related hormonal disruption
Related Biomarkers
Frequently Asked Questions
What are the symptoms of high prolactin levels?
High prolactin (hyperprolactinemia) can cause a range of symptoms depending on sex. In women, symptoms often include irregular or absent menstrual periods, difficulty getting pregnant, unexpected breast milk production (galactorrhea), and low libido. In men, symptoms may include reduced sex drive, erectile dysfunction, infertility, and in some cases breast tissue enlargement (gynecomastia). Both men and women may experience headaches, vision changes, and bone loss if a pituitary tumor (prolactinoma) is the cause.
Can stress cause prolactin levels to be high?
Yes, acute physical and psychological stress can temporarily raise prolactin levels. Activities such as intense exercise, a venipuncture procedure itself, sexual activity, or emotional distress in the hours before a blood draw can all cause a transient spike. This is why doctors often recommend repeating the test under calm, resting conditions if an initial result is mildly elevated. Chronic stress may also have sustained effects on pituitary hormone regulation.
Do I need to fast before a prolactin blood test?
Fasting is not strictly required for a prolactin test, but several precautions are recommended for accuracy. It is best to have blood drawn in the morning (prolactin is higher during sleep and peaks shortly after waking), avoid vigorous exercise for several hours beforehand, avoid nipple stimulation, and try to be in a relaxed state. Eating a high-protein meal has been shown to suppress prolactin somewhat, so some clinicians recommend fasting for 1–2 hours prior to the test.