Prolactin test (PRL) Biomarker Testing
A prolactin test measures a pituitary hormone tied to lactation and reproductive signaling; order it with Vitals Vault and test at Quest locations.
With Vitals Vault, you have access to a comprehensive range of biomarker tests.
Prolactin is a hormone made by your pituitary gland. It is best known for supporting breast milk production after pregnancy, but it also interacts with your reproductive hormones and can affect libido, menstrual cycles, and testosterone signaling.
A prolactin blood test is usually ordered when symptoms suggest a hormone imbalance or when a clinician wants to rule out medication effects or pituitary causes. Because prolactin can rise temporarily from stress, sleep, or nipple stimulation, a single result often needs context before you draw conclusions.
Your number is most useful when you pair it with your symptoms, your medication list, and a few related labs. Testing can support clinician-directed care, but it cannot diagnose a condition by itself.
Do I need a Prolactin test?
You may want a prolactin test if you are trying to explain reproductive or sexual symptoms that do not have a clear cause. In people with ovaries, prolactin is commonly checked for irregular or absent periods, infertility, unexpected breast milk leakage (galactorrhea), or persistent low libido. In people with testes, it is often checked when testosterone is low, libido is low, erections are difficult to maintain, or fertility is a concern.
A prolactin test can also be helpful if you have symptoms that raise concern for a pituitary issue, such as new headaches or changes in vision, especially peripheral vision. Clinicians may order it when other hormone tests are abnormal, because the pituitary coordinates several hormone systems.
You may not need this test if you feel well and have no symptoms, because mild elevations can be temporary and clinically insignificant. If you do test and the result is abnormal, the next step is usually to confirm it and look for a cause rather than treating a number in isolation.
This is a standard blood test performed in CLIA-certified labs; results should be interpreted with your clinician and are not a standalone diagnosis.
Lab testing
Order a prolactin test and choose a Quest draw location
Schedule online, results typically within about a week
Clear reporting and optional clinician context
HSA/FSA eligible where applicable
Get this test with Vitals Vault
If you want a clear, documented baseline for prolactin, Vitals Vault lets you order the lab test directly and complete your blood draw at a nearby Quest location. This can be useful when you are preparing for a clinician visit, comparing repeat results over time, or monitoring a known issue.
After your result posts, you can use PocketMD to talk through what the number may mean for you, what common follow-up tests are worth discussing, and when a repeat draw is reasonable. Prolactin is a marker where timing and context matter, so having a plan for confirmation testing can prevent unnecessary worry.
If your prolactin is meaningfully elevated, you can use Vitals Vault to recheck it under more controlled conditions (for example, a morning draw after avoiding triggers) and to add companion hormone tests that help explain the “why.”
- Order online and test at Quest locations
- Clear results you can share with your clinician
- PocketMD guidance for next steps and retest timing
Key benefits of Prolactin testing
- Helps explain irregular periods, infertility, or unexpected lactation when pregnancy is not the cause.
- Adds context to low testosterone or sexual symptoms by checking for prolactin-related suppression of gonadotropin signaling.
- Supports medication review, since several common drugs can raise prolactin and mimic endocrine disease.
- Helps screen for pituitary-related causes when symptoms include headaches, vision changes, or multiple hormone abnormalities.
- Guides follow-up decisions, such as whether you should repeat the test under controlled conditions or add macroprolactin testing.
- Improves interpretation when paired with thyroid and reproductive hormones, which often shift alongside prolactin.
- Makes it easier to track trends over time, especially when you use PocketMD to plan consistent retesting.
What is Prolactin?
Prolactin (often abbreviated PRL) is a hormone produced by your pituitary gland, a small gland at the base of your brain that helps regulate many endocrine systems. Prolactin’s most recognized role is supporting breast development and milk production after childbirth, but it also interacts with the hypothalamus and reproductive hormones.
In general, higher prolactin levels can reduce the release of gonadotropin-releasing hormone (GnRH), which can lower luteinizing hormone (LH) and follicle-stimulating hormone (FSH). That downstream effect can contribute to irregular ovulation, reduced estrogen or testosterone signaling, and fertility challenges.
Prolactin is naturally dynamic. It tends to rise during sleep, can increase with physical or emotional stress, and may increase with nipple or chest wall stimulation. Because of that, clinicians often prefer a morning blood draw and may repeat the test if the first result is only mildly abnormal.
Why prolactin can be high without a tumor
A high result does not automatically mean a prolactinoma (a prolactin-secreting pituitary adenoma). Hypothyroidism, pregnancy, breastfeeding, kidney disease, and several medications can raise prolactin. Even a difficult blood draw or acute stress can cause a temporary bump, which is why confirmation testing is common.
Macroprolactin and “false” elevations
Some people have higher measured prolactin because of macroprolactin, a larger prolactin complex that can show up on certain assays but is often less biologically active. If your prolactin is elevated but you have few or no symptoms, your clinician may consider a macroprolactin evaluation depending on the lab and clinical picture.
What do my Prolactin results mean?
Low prolactin levels
Low prolactin is less commonly a clinical problem than high prolactin. It can be seen with certain pituitary disorders, after pituitary surgery or radiation, or with medications that increase dopamine activity. If you are postpartum and having difficulty producing milk, low prolactin may be one piece of the puzzle, but it is not the only factor. Your clinician usually interprets low prolactin alongside other pituitary hormones and your symptoms.
In-range (typical) prolactin levels
An in-range prolactin result generally suggests your pituitary is not overproducing prolactin at the time of the draw. If you still have symptoms like irregular periods, infertility, or low libido, your clinician may look at other drivers such as thyroid function, ovarian/testicular hormones, or medication effects. Because prolactin fluctuates, “normal” does not rule out every pituitary issue, but it makes significant prolactin excess less likely. Trend and context matter more than a single data point.
High prolactin levels
High prolactin (hyperprolactinemia) can contribute to menstrual changes, infertility, reduced libido, and low testosterone or estrogen signaling. Mild elevations are often due to stress, recent sleep, nipple stimulation, or medications, and they are frequently confirmed with a repeat morning test. More marked or persistent elevations raise concern for endocrine causes such as hypothyroidism or, less commonly, a prolactin-secreting pituitary adenoma. If your level is very high or you have headaches or vision changes, your clinician may discuss additional pituitary evaluation.
Factors that influence prolactin
Timing and conditions of the blood draw can change your result, since prolactin rises during sleep and can increase with stress or pain. Pregnancy and breastfeeding raise prolactin physiologically, and chest wall stimulation or injury can also increase it. Medications are a major confounder, including some antipsychotics, antidepressants, anti-nausea drugs, and opioids, so bring a complete list to your review. Thyroid status matters too, because untreated hypothyroidism can elevate prolactin through increased TRH signaling.
What’s included
- Prolactin
Frequently Asked Questions
Do I need to fast for a prolactin blood test?
Fasting is not usually required for prolactin. What matters more is timing and conditions, since prolactin can rise with sleep and stress. If you are repeating an abnormal result, your clinician may suggest a morning draw and avoiding triggers like intense exercise beforehand.
What time of day should prolactin be tested?
Prolactin follows a daily rhythm and is often higher during and shortly after sleep. Many clinicians prefer a morning blood draw, ideally after you have been awake for a bit and are relatively relaxed. If your first result is mildly high, repeating it under consistent morning conditions can improve interpretability.
Can stress or exercise raise prolactin?
Yes. Physical stress, emotional stress, pain, and vigorous exercise can temporarily increase prolactin. Even anxiety about the blood draw can contribute, which is one reason mild elevations are commonly rechecked.
What medications can increase prolactin?
Several medications can raise prolactin, especially drugs that block dopamine signaling. Examples include some antipsychotics, certain antidepressants, anti-nausea medications, and opioids. Do not stop a prescription medication on your own, but do bring a complete list to your clinician so the result is interpreted correctly.
How high does prolactin have to be to suspect a prolactinoma?
There is no single cutoff that diagnoses a prolactinoma from labs alone, and reference ranges vary by lab. In general, higher and persistent elevations are more concerning than mild, one-time increases, especially when symptoms are present. Your clinician may repeat the test, review medications and thyroid status, and consider imaging if the pattern suggests a pituitary source.
What follow-up tests are commonly ordered with prolactin?
Follow-up depends on your symptoms, but common companions include TSH (and sometimes free T4) to assess thyroid status, LH and FSH to evaluate pituitary-gonadal signaling, and estradiol or testosterone with SHBG. If an elevation seems inconsistent with symptoms, a macroprolactin evaluation may be considered. Your clinician may also review kidney function and pregnancy status when relevant.
Should I retest prolactin if it is slightly high?
Often, yes. Mild elevations are frequently due to temporary factors, so clinicians commonly confirm with a repeat morning test under calmer, more standardized conditions. Retesting is especially useful if you had a stressful draw, you were sleep-deprived, or you recently exercised.