Prolactin is a hormone made by the pituitary gland that drives milk production after birth and also affects the reproductive hormones. The prolactin page covers its normal range by sex and life stage.

Can stress cause high prolactin?

Yes. Physical and emotional stress raise prolactin, and even the stress of a difficult blood draw can push a reading just above the range. Stress usually causes only a small rise, so a clearly higher result needs a cause looked for.

What prolactin level indicates a tumor?

Above 500 ng/mL suggests a large prolactinoma (10 mm or more), and the table above shows the lower bands. Smaller tumors can sit in the 25 to 100 ng/mL range, and a very large tumor can read falsely low because of the hook effect, so the number guides the workup without settling it.

Does high prolactin cause weight gain?

Weight gain, fatigue and mood change are not reliable signs of high prolactin. The dependable signs are changes to periods, milk discharge, low libido and, with a large tumor, headaches or vision changes.

Can high prolactin go away on its own?

A rise from stress, exercise or a bad draw usually settles on a calm repeat test. A rise from a medication or hypothyroidism falls once the cause is dealt with. Some small prolactinomas stay stable or shrink without treatment, which is why monitoring is sometimes enough.

Can you get pregnant with high prolactin?

High prolactin often stops ovulation, which makes getting pregnant harder. Once prolactin is brought down, ovulation usually returns. Prolactin also rises naturally in pregnancy, so a pregnancy test is one of the first checks after a high result. The fertility page covers the other tests worth doing.

How do you lower high prolactin levels naturally?

There is no well-tested natural way to lower a true high prolactin. Avoiding stress, hard exercise and nipple stimulation before the test gives a more accurate reading. A real rise is lowered by treating its cause, such as hypothyroidism, or with a prescribed dopamine agonist for a prolactinoma.

High prolactin level: what counts as high, the causes

The distinctions

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How far above range prolactin sits sorts the cause before any scan
Just above range is usually the draw, a drug, the thyroid or the kidneys; above about 250 ng/mL it usually points to a prolactinoma, unless a drug such as risperidone explains it ¹. Two exceptions keep the number from settling it alone: a small tumor can sit at 25 to 100 ng/mL, and a very large one can read falsely low because of the hook effect ⁴.

Hyperprolactinemia, the medical name for high prolactin, is common and usually explainable. How far above the range your prolactin sits is the best single clue to why it is high: a reading of 30 ng/mL and a reading of 300 ng/mL lead to very different next steps. Prolactin is made by the pituitary, a pea-sized gland under the brain, and its main job is driving milk production; the prolactin page covers what it does day to day. This page covers what a high result means and how doctors work it out.

Where an example prolactin of 42 ng/mL fallsng/mL

42 ng/mLMild to moderate · same as about 890 mIU/L

Typical range0–25Mild to moderate: draw stress, drugs, thyroid, kidney25–100High: drugs or prolactinoma100–250Very high: usually prolactinoma250–300

A prolactin of 42 ng/mL is a mild rise. Your doctor will usually repeat it if the draw was stressful, then check medications, thyroid and kidney function before considering a scan.

Upper limits vary by lab and sex (roughly 25 ng/mL in women, 15 to 20 ng/mL in men). The bands are approximate and overlap, drawn from the Endocrine Society guideline ¹ and Vilar et al. ⁴. Convert ng/mL to mIU/L by multiplying by about 21.2 ⁴.

How high is high: the bands and what they point to

Labs report prolactin in ng/mL or mIU/L, and the two differ by a factor of about 21.2, so 25 ng/mL is about 530 mIU/L ⁴. Pregnancy is the exception to every band below: prolactin climbs steadily through pregnancy to roughly 10 times the non-pregnant level by term ¹.

Prolactin band	ng/mL	mIU/L (approx.)	Usual explanations
Mild (just above range)	Upper limit to about 40	Upper limit to about 850	Stress of the draw, recent exercise, sleep, nipple stimulation, macroprolactin (an inactive form, see below)
Mild to moderate	40 to 100	850 to 2,100	Medications, primary hypothyroidism, kidney disease, PCOS (polycystic ovary syndrome), microprolactinoma (a small benign tumor under 10 mm)
High	100 to 250	2,100 to 5,300	Antipsychotics such as risperidone, metoclopramide, prolactinoma
Very high	Above 250	Above 5,300	Usually a prolactinoma, though some drugs can reach this range; above 500 ng/mL suggests a macroprolactinoma

The Endocrine Society guideline notes that a prolactin above 250 ng/mL usually indicates a prolactinoma, while drugs like risperidone and metoclopramide can push prolactin above 200 ng/mL with no tumor at all ¹. A level above 500 ng/mL suggests a macroprolactinoma, a tumor 10 mm or larger ¹⁴. One trap runs the other way: a very large tumor can make so much prolactin that the test reads falsely low or only mildly high, called the hook effect. Diluting the sample and running it again gives the true value, which is why a large pituitary tumor with a modest prolactin needs a diluted retest ¹⁴.

What causes high prolactin

Dopamine from the brain acts as a constant brake on prolactin release. Anything that weakens that brake (a drug that blocks dopamine, or a tumor pressing on the pituitary stalk that carries dopamine down) lets prolactin rise. The common causes fall into five groups.

Normal body states: pregnancy, breastfeeding, sleep, physical or emotional stress, hard exercise, nipple or chest stimulation.
Medications: antipsychotics are the most common drug cause, with risperidone and amisulpride raising prolactin most and aripiprazole tending to lower it ⁴. Metoclopramide, domperidone, some antidepressants, opioids, verapamil, methyldopa and estrogen can also raise it.
Thyroid and kidneys: in primary hypothyroidism, high TRH (the brain signal that drives the thyroid) also stimulates prolactin, and the rise settles with thyroid hormone replacement ¹⁴. Chronic kidney disease slows prolactin clearance, and high prolactin is found in about 30% of people with CKD and up to 80% of people on dialysis ⁴.
Less common conditions: cirrhosis, PCOS, chest-wall injury or shingles, and seizures can also raise it.
Pituitary tumors: a prolactinoma, which is the most common hormone-making pituitary tumor at about 40% of pituitary adenomas ⁵, or a different pituitary tumor pressing on the stalk.

Before a scan, the guideline asks doctors to rule out medications, kidney failure, hypothyroidism and tumors near the pituitary ¹. The hypothyroidism, chronic kidney disease and PCOS pages cover those conditions in full.

Read these beside a high prolactin

Thyroid Stimulating HormoneA high TSH points to hypothyroidism as the cause Free ThyroxineConfirms whether the thyroid is underactive Estimated Glomerular Filtration RateShows whether the kidneys are clearing prolactin

Symptoms of high prolactin in women and men

How high prolactin turns into symptoms

Prolactin rises

From a drug, a tumor, the thyroid or the kidneys.

GnRH pulses slow

High prolactin quiets the brain signal that starts the reproductive hormone chain.

LH and FSH fall

The pituitary releases less LH and FSH, the two hormones that tell the ovaries or testes to work.

Estrogen or testosterone drops

Periods change, libido falls, fertility drops, and over years bone density can thin.

Mechanism as described in the Endocrine Society guideline ¹ and NIDDK ⁵.

In women, high prolactin causes irregular or missed periods, trouble getting pregnant, a milky nipple discharge when not breastfeeding, vaginal dryness and low libido ⁵. In men, it causes low libido, erectile problems, low testosterone, breast enlargement and reduced fertility ⁵. Men often notice later, so men's tumors tend to be larger when found ².

A large prolactinoma, called a macroprolactinoma (10 mm or bigger), can also press on the optic nerves just above the pituitary and cause headaches and loss of side vision ⁵. Many people with a high result have no symptoms at all.

When a high result causes no symptoms

Your next steps after a high prolactin result

To establish the diagnosis of hyperprolactinemia, we recommend a single measurement of serum PRL; a level above the upper limit of normal confirms the diagnosis as long as the serum sample was obtained without excessive venipuncture stress.Endocrine Society clinical practice guideline, 2011 ¹

In plain words: one prolactin test above the range is enough to call it high, as long as the blood draw itself was not stressful.

1Repeat the prolactin blood test if borderlineIf prolactin was only just above the range, or the draw was stressful, a calm repeat often comes back normal. Ask for it on a different day, a few hours after waking, after sitting quietly for a while, with no hard exercise or nipple stimulation beforehand. The guide on how to prepare for a blood test covers timing.
2List every medicationBring all prescriptions to your doctor. Never stop an antipsychotic or other prescribed drug on your own; a switch is a decision for your prescriber.
3Rule out the common causesA pregnancy test, TSH and free T4 (see how to read your thyroid panel), and kidney function (kidney function explained) come before any scan ¹.
4Ask about macroprolactinIf you have no symptoms, a PEG test can show whether the prolactin is the inactive form ³.
5See what it is doing downstreamLH, FSH and estradiol or testosterone show whether prolactin is suppressing the reproductive hormones ¹.
6Pituitary MRI if it stays unexplainedOnce drug, thyroid and kidney causes are excluded, a persistent unexplained rise is usually followed by an MRI of the pituitary, a decision your doctor makes ¹.
7Who to seeIf prolactin stays high with no clear cause, or you have symptoms, ask your doctor for a referral to an endocrinologist (a hormone specialist).

The follow-up markers

Luteinizing HormoneLow LH (read with FSH) shows prolactin is suppressing the hormone chain Estradiol (E2)Low estradiol explains missed periods and bone risk Testosterone, TotalLow testosterone explains low libido in men

If your estradiol also came back low, see low estradiol. Long-standing low estrogen or testosterone can thin bones; bone markers explained covers how that is checked. The female hormone panel and male hormone panel guides walk through the rest, and reference ranges explained covers why your lab's cutoff may differ from the numbers here.

How to lower high prolactin: treatment

Treatment follows the cause. Treating hypothyroidism brings prolactin down ¹, and a prescriber may change a drug that raises it. A mild rise with no symptoms, or a small microprolactinoma in someone with regular periods and no fertility plans, may only need monitoring, and some small tumors stay stable or shrink without treatment ¹².

80 to 85%of people with a microprolactinoma reach a normal prolactin on cabergoline (rates are somewhat lower for large tumors)Pituitary Society consensus, 2023 ²

For a prolactinoma that causes symptoms, the first treatment is a dopamine agonist, a drug that restores the dopamine brake. The guideline prefers cabergoline over bromocriptine because it normalizes prolactin and shrinks the tumor more often ¹. Prolactin is rechecked about a month after starting or changing the dose, then periodically, and for most women with a small tumor the drug is stopped once pregnancy is confirmed, a plan made with an endocrinologist ¹². Surgery is kept for people who cannot tolerate the drug or whose tumor does not respond ².

Guidelines recommend no supplement for lowering prolactin; treatment means dealing with the cause or taking a dopamine agonist ¹². Lowering stress before a blood draw gives a more accurate reading but does not treat a real rise.

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Citations

Educational context only, not medical advice or a diagnosis. Always discuss your results with a clinician.

High prolactin level: what counts as high, the causes and what to do next