Prolactin (PRL)
Most hormones report what your body is doing. Prolactin can report what the needle did: the stress of the draw, a dopamine-blocking pill, or an inert decoy molecule can all push it up while you feel completely fine.
Part of the Hormone Panel — see all 21 values together, including 17-Hydroxyprogesterone, Aldosterone, Androstenedione.
Most hormone tests report what the body is doing. Prolactin can report what the needle did. It is one of the few results on a panel where the act of taking the blood, a stressful sprint to the lab, or a large decoy molecule the assay can't tell apart from the real thing can lift the number while nothing is actually wrong. So the most common reaction to a flagged prolactin, a quiet panic about a brain tumor, is usually aimed at the least likely explanation.
Prolactin, abbreviated PRL, is made by the pituitary gland at the base of the brain, and its headline job is to grow breast tissue in pregnancy and drive milk production after birth, as MedlinePlus describes it. Outside of that, the brain keeps it on a short leash. The hypothalamus holds prolactin down almost constantly, and the rope it pulls is dopamine: StatPearls describes prolactin's control as primarily inhibitory, run through dopamine. Think of dopamine as a parking brake the brain keeps pulled. Most of the time the brake is set and prolactin idles low. Lift the brake, or weaken it, and prolactin rolls upward on its own. That single picture explains nearly everything this number does.
One label note before the bands. US labs report prolactin in ng/mL; many report in mIU/L, where the figures run far apart (a result near 20 ng/mL is roughly 425 mIU/L), so check which unit sits beside your number before comparing it to anything.
Reading a prolactin value
ng/mLLow prolactin is rare and rarely a problem on its own. MedlinePlus notes a low result can point to a pituitary that is underactive overall, so it is read in the context of the other pituitary hormones rather than alone.
The usual resting band, with women sitting a little higher than men. StatPearls puts average basal levels near 13 ng/mL in women and 5 in men. Exact cutoffs vary by lab, so read against your own report.
The zone where the parking-brake explanations live: a medication, the stress of the draw, an early-morning or post-exercise sample, or the macroprolactin artifact. This is the range most often rechecked before anything else is done.
Climbing well above 100 ng/mL narrows the list. StatPearls notes causes other than a tumor rarely exceed 200 ng/mL, so a high value, especially with symptoms, is what prompts a doctor to consider pituitary imaging.
The amber band is where the avoidable worry happens. A prolactin of 40 reads as a red flag to someone expecting a fixed ceiling, but it sits squarely in the territory a single repeat draw often resolves. The number's height is the real signal: a mild rise points one way, a value in the hundreds or thousands points another.
What does a high prolactin mean?
A high prolactin (hyperprolactinemia) means more is circulating than the lab's range allows. Before any of it counts as real, three things that lift the value without a true rise in active hormone have to be ruled out.
What can push prolactin high
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The stress of the draw
Prolactin climbs transiently with physical and emotional stress; StatPearls lists surgery and heart attack among the triggers. The venipuncture and a rushed arrival can be enough to lift a borderline value, which is why repeating the draw sometimes brings it back to normal.
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Dopamine-blocking medications
Releasing the brake. Antipsychotics are a leading cause, with risperidone producing some of the largest rises (sometimes above 100–200 ng/mL per StatPearls); some anti-nausea drugs and antidepressants raise it more mildly.
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Macroprolactin
A large, biologically inactive complex of prolactin and antibody that the assay still counts. It accounts for roughly one in five elevated samples, causes no symptoms, and needs no treatment once it is identified.
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Pregnancy and breastfeeding
The hormone's actual day job. Levels rise substantially through pregnancy and with nursing, which is normal physiology rather than a finding.
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Underactive thyroid
In primary hypothyroidism the signal that drives TSH also nudges prolactin up; StatPearls notes 20–40% of people with hypothyroidism have some hyperprolactinemia, which often settles once the thyroid is treated.
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A prolactinoma
A benign pituitary tumor of the prolactin-making cells, and the cause people fear first. It can produce anything from a mild rise to extreme levels, and the higher the number, the more it moves up the list.
When prolactin is genuinely high, the symptoms trace back to its effect on the reproductive hormones. Prolactin suppresses the release of GnRH, the upstream signal that drives luteinizing hormone and FSH, so a sustained elevation can quiet the whole downstream cycle. MedlinePlus describes the result in women as changes in menstruation, milk production or nipple discharge outside of nursing, and trouble conceiving. In men it can show up as reduced sex drive, erectile difficulty, breast enlargement, or nipple discharge, which is why a man's prolactin is sometimes checked during a low-testosterone or fertility workup rather than dismissed. Because a pituitary tumor can disturb more than one hormone at once, a high prolactin sometimes prompts a look at IGF-1 to check for excess growth hormone.
What does a low prolactin mean?
Low prolactin gets far less attention because it rarely causes trouble on its own. MedlinePlus notes that low results are uncommon and, when they matter, usually point to a pituitary gland that is underactive across the board rather than a prolactin-specific problem. For that reason a low value is interpreted alongside the other pituitary outputs, not in isolation. One of those outputs is ACTH, the pituitary's signal to the adrenal glands, which is why a broadly underactive pituitary tends to show up across several of these hormones at once rather than in prolactin alone. Prolactin is one of several pituitary hormones interpreted in context with neighbors like growth hormone, whose levels also swing with stress, sleep, and the clock. Most people who notice a low-ish prolactin on a report have nothing to act on.
If a prolactin result came back high
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Ask your doctor whether to simply repeat it
A mild elevation is often rechecked first, ideally mid-morning, fasting, and after a calm arrival rather than a rush. Because the draw itself can lift the value, a second sample frequently resolves a borderline result without any further testing.
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2
Tell your doctor about every medication
Dopamine-blocking drugs are a common, fixable cause. The decision to adjust or continue a medication belongs to the doctor who prescribed it, weighed against why it was started, never changed on your own.
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3
Ask whether macroprolactin was screened
Labs can treat the sample with polyethylene glycol to remove the inactive macroprolactin and remeasure the active hormone. StatPearls notes this step prevents an unnecessary workup, and that macroprolactinemia itself needs no treatment.
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4
Have thyroid checked alongside it
Because an underactive thyroid can drive prolactin up, clinicians often read it together with a thyroid panel, since treating the thyroid can bring a mildly high prolactin back down.
Where prolactin fits, and why one number rarely settles it
Prolactin sits on the hormone panel and is read against the markers it influences. Because it puts a brake on the reproductive axis, it is interpreted beside LH and FSH, the pituitary's signals to the gonads, and beside estradiol or testosterone depending on the question being asked. The guide to reading a hormone panel walks through interpreting these together rather than reacting to a single flag, and the comparison of LH and FSH shows the downstream pair prolactin can suppress.
Because so much of what moves prolactin is timing, stress, and assay quirks, a single high reading says less than the same draw repeated under the same conditions. A borderline value that settles on a calm morning recheck tells a very different story from one that holds high across several draws, which is why a mild elevation is usually a question of how soon to recheck rather than what to do today.
Sources
Written and reviewed by BloodSight Editorial Team · Last updated
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In your personal range
Normal ranges
| Group | Range | Unit |
|---|---|---|
| Adult Female | 5–25 | ng/mL |
| Adult Male | 3–13 | ng/mL |
Reference ranges may vary by laboratory and individual factors.
Prolactin — Common Questions
What is a normal prolactin level?
I have high prolactin but feel completely fine. What does that mean?
Which medications raise prolactin?
Can stress cause high prolactin?
What prolactin level suggests a prolactinoma?
When should prolactin be tested?
Disclaimer
This content is for informational and educational purposes only. It is not intended as medical advice, diagnosis, or treatment recommendation. Reference ranges may vary by laboratory. Always discuss your results with a qualified healthcare professional.
Related Tests
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FSH is the pituitary's bid for the next egg, and the bid climbs as the ovaries' supply runs down. Read on the wrong cycle day, or without its partner hormones, a single number says far less than it looks like it does.
Estradiol runs on the menstrual calendar, climbing roughly tenfold from the start of a cycle to the day before ovulation. Read without the day it was drawn, the number on your report can look alarming and mean almost nothing.
Total testosterone counts every molecule of the hormone in your blood, but most of it is locked away and unavailable. That gap is why a normal result and real symptoms can sit on the same report.
TSH is the most ordered thyroid test, and the most counterintuitive one to read, because the number moves in the opposite direction from your thyroid.
ACTH is the pituitary's order to the adrenal glands to make cortisol. On its own the number means little. Paired with a cortisol that has already come back wrong, it points to where the fault sits.
Growth hormone pulses through the day in bursts no single blood draw can catch. IGF-1 is the steady downstream level clinicians read instead, and reading it wrong cuts both ways.
Growth hormone is the rare result confirmed by deliberately pushing it down or driving it up, not by reading it where it sits.