Prolactin test for women: what it checks and how to prepare
Prolactin is a hormone made by the pituitary gland at the base of the brain. Its main job is to signal breast tissue to grow in pregnancy and make milk after birth. In women who are not pregnant or breastfeeding, prolactin is normally low. A prolactin test is most often ordered when something about periods, fertility or breast discharge needs an explanation.
Prolactin
A single blood test for prolactin, a pituitary hormone linked to periods, fertility and milk production.
$59
See this test at HealthLabsPrice checked October 2026. Not available in ND, RI, NY, NJ, MD and HI. We earn a commission on sales.
When a prolactin test is ordered
MedlinePlus says a prolactin test is most often used, with other tests, to:
- Diagnose a prolactinoma, a benign tumor on the pituitary gland
- Find the cause of irregular menstrual periods
- Find the cause of infertility
- Monitor a known prolactinoma to see if treatment is working
In women, symptoms that may lead to the test include changes in menstruation (irregular or absent periods), breast milk when not pregnant or breastfeeding, nipple discharge and infertility.
Prolactin is also one of the labs used to rule out other causes when PCOS is suspected. The 2023 international PCOS guideline lists prolactin, with TSH, 17-hydroxyprogesterone and FSH, for excluding other conditions. See PCOS tests.
Preparing for the test
- Time of day. MedlinePlus says prolactin changes through the day, so the sample is usually scheduled three to four hours after you wake up.
- Fasting. The seller’s page says fasting is not required for this order. MedlinePlus says you may be asked to fast for several hours, so follow the instructions on your lab order if you have one.
- Medicines and vitamins. MedlinePlus says certain medicines and vitamins can affect prolactin levels. Tell whoever orders or reads your test about everything you take. Never stop a medicine without talking to your clinician.
- Biotin. Lab information for one prolactin method says that if you take high-dose biotin (over 5 mg a day), a sample should be taken at least eight hours after the last dose. Ask the lab if this applies to you.
If you could be pregnant, or you are breastfeeding, tell a clinician. Prolactin is normally high at those times.
A published range for women
Ranges depend on the lab and the method, so use the range on your own report. As a published example, one national reference lab lists these female ranges:
| Age | Female prolactin range (ng/mL) |
|---|---|
| 13 to 30 | 4.8 to 33.4 |
| 31 to 50 | 4.8 to 33.4 |
| 51 to 80 | 3.6 to 25.2 |
| 81 and over | 3.6 to 32.0 |
Source: Labcorp test directory, prolactin. A result inside or outside a range does not diagnose anything. Talk with a clinician about your own result.
Labs do not agree with each other. A 2024 study from Amsterdam compared two prolactin immunoassays on the same samples and found one gave results 1.75 times higher than the other, even though the manufacturers’ reference intervals were similar. That is a reason to compare your result to the range on your own report, not to a number from a website.
What the result can mean
A prolactin test cannot show the cause of a high level, MedlinePlus says. It helps a provider decide which other tests you need. Higher-than-normal results can come from many causes, including a prolactinoma, other pituitary or hypothalamus conditions, an underactive thyroid, kidney disease, liver scarring (cirrhosis), PCOS and certain medicines. Small rises can come from stress, exercise and even sex, so a clinician may suggest repeating the test.
Lower-than-normal prolactin is rare. MedlinePlus says it may be a sign of a pituitary disorder, and that the usual symptom is not making enough milk to breastfeed.
Read more about high prolactin.
When to see a clinician
Take an out-of-range result to a clinician, along with your symptoms and a list of what you take. If a high result comes with headaches or changes in your vision, get seen promptly. MedlinePlus says a prolactinoma that is not treated can grow large enough to press on nearby structures, causing both.
Prolactin
$59
See this test at HealthLabsPrice checked October 2026. Not available in ND, RI, NY, NJ, MD and HI. We earn a commission on sales.
Keep reading
- High prolactin in women: causes and what a high result means
High prolactin has many possible causes, from medicines to a pituitary tumor. See what a high result can mean, what happens next and when to see a clinician.
- PCOS tests: which blood tests doctors order and which fit
No single blood test diagnoses PCOS. See how the international guideline diagnoses it, which labs are typically ordered, and the lowest-priced fits.
- Testosterone test for women: which one to order
Women make testosterone too. See what the test measures, total versus free, a published range for women, and which blood test is the lowest-priced fit.
Sources
- Prolactin Levels (MedlinePlus)
- Prolactin test information and reference range (Labcorp test directory)
- Confusion in the interpretation of prolactin levels caused by inappropriately low reference intervals (Endocr Connect, 2024)
- Recommendations From the 2023 International Evidence-based Guideline for the Assessment and Management of Polycystic Ovary Syndrome (J Clin Endocrinol Metab, 2023)