Prolactin

Blood test

Also known as: PRL, Serum prolactin

There is no single guideline cutoff for prolactin. The result is read against the lab's sex-specific range with a clinician, and a mildly high result is usually repeated.

A level above 200 ng/mL makes a prolactin-secreting pituitary tumor more likely than other causes (Pituitary Society, 2023).

Prolactin is a hormone made by the pituitary gland, best known for its role in making breast milk. When it runs too high, it lowers the hormones that drive testosterone and estrogen. That can cause low desire, erection problems, infertility and menstrual changes.

What it tells you

Dopamine from the brain normally holds prolactin down. Estrogen and some brain signals push it up, and the kidneys clear it.
High prolactin switches off the brain signal that drives the testes and ovaries. Testosterone or estrogen then falls.
One high result from a calm, unstressed draw confirms high prolactin. A level less than five times the lab's upper limit is usually repeated.
Causes range from a pituitary tumor called a prolactinoma to medicines, an underactive thyroid, kidney disease and pregnancy.
Some blood carries a large, inactive form called macroprolactin. It reads as high on many tests but does not act like the hormone, and a separate lab step detects it.
A 2023 consensus says loss of desire or infertility should prompt a prolactin test. In men, so should erection problems or low testosterone from a pituitary cause.

What can throw it off

The stress of a needle stick can raise it two- to fourfold for under an hour. A high result is often repeated with a calmer draw.
Sleep, exercise, sex, high-protein meals, alcohol and breast or nipple stimulation can raise it. So can chest-wall injuries, piercings or surgery.
Pregnancy and breastfeeding raise it naturally.
Many medicines raise it, including antipsychotics, metoclopramide, some antidepressants, opioids, verapamil and estrogens. Levels usually settle within about three days of stopping, but antipsychotics are never stopped without the prescriber.
An underactive thyroid, kidney disease and liver cirrhosis can raise it.
Macroprolactin, the inactive form, can make a result look high when the active hormone is not.
Rarely, a very large tumor makes the result read falsely low on some tests. Diluting the sample fixes this.
Biotin supplements can distort the result on some lab machines.

Evidence

Confirming high prolactin

Early human evidenceCEBM Level 4

Guidelines strongly back one high result from a calm, unstressed draw as enough to confirm it. Needle-stick stress can raise prolactin two- to fourfold for under an hour, so a mild rise is often repeated.

Predicting a pituitary tumor from the level

Early human evidenceCEBM Level 4

Case series show that higher levels make a prolactinoma more likely. The cutoff differs: 200 ng/mL in a 2023 consensus and 250 ng/mL in a 2011 guideline. Some medicines push prolactin above 200 ng/mL without a tumor, and small tumors can run high.

Routine testing in men with erection problems

Some human evidenceCEBM Level 2b

In two studies of over 1,400 men each, high prolactin turned up in under 2% and a prolactinoma in under 0.5%. That supports testing men with specific clues, such as low desire, low testosterone or breast growth.

Limits

The cutoff is each lab's own upper limit, which varies by method and by sex. Results cannot be compared across labs.
A slightly high result is common and usually harmless. Stress, a medicine or macroprolactin often explains it.
One value can mislead. A mild rise is repeated, ideally from a calm draw, before any scan.
The level only loosely predicts tumor size. Other pituitary masses can cause modest rises.
Most men with erection problems have a prolactin within the lab's range, so guidelines favor targeted testing.
A low prolactin is not a recognized diagnosis in adults.

References

Reviewed by Shubham Gupta, MD — Founder & President · November 5, 2026

This page is for education only. It is not medical advice. Decisions about any treatment belong with a physician who knows your history.