A high prolactin level usually means something is stimulating your pituitary gland to produce more of this hormone than normal. Normal prolactin sits below 20 ng/mL in men and below 25 ng/mL in non-pregnant women. When levels rise above those thresholds, the cause can range from something as harmless as stress or poor sleep to a pituitary tumor or a medication side effect. The key is figuring out which category you fall into, because that determines whether you need treatment at all.
What Prolactin Does in Your Body
Prolactin is best known for triggering breast milk production after childbirth, but it plays a broader role in reproductive function for everyone. It’s produced by the pituitary gland, a pea-sized structure at the base of your brain, and its release is kept in check by dopamine. When dopamine levels drop or something blocks dopamine’s signal, prolactin rises.
The reason high prolactin causes so many symptoms is that it disrupts a hormonal chain reaction. Elevated prolactin suppresses a signaling hormone in the brain that tells the pituitary to release the hormones controlling your ovaries or testes. The result: your body dials down its production of estrogen or testosterone. This single disruption explains most of the symptoms people experience, from irregular periods to low sex drive to difficulty conceiving.
Causes That Don’t Require Treatment
Before assuming something is wrong, it’s worth knowing that prolactin spikes temporarily for a long list of everyday reasons. Stress (including the stress of having blood drawn), exercise, sleep, sexual activity, nipple stimulation, a high-protein meal, and even low blood sugar can all push prolactin above normal range. Prolactin secretion is pulsatile, peaking during deep sleep between roughly 4 and 6 AM. A blood draw taken early in the morning or right after a stressful event can return a mildly elevated result that doesn’t reflect a real problem.
Pregnancy is the most common physiological cause of significantly high prolactin. Levels in pregnant women can climb as high as 500 ng/mL, which is entirely normal. During breastfeeding, prolactin stays elevated to support milk production.
Medications That Raise Prolactin
Medications are the most common non-tumor cause of genuinely elevated prolactin. Antipsychotic drugs top the list because they block dopamine receptors directly, removing the brake that normally keeps prolactin in check. Older antipsychotics like haloperidol and chlorpromazine are well-known for this, but newer ones like risperidone and amisulpride raise prolactin just as reliably.
Antidepressants that affect serotonin, including SSRIs like sertraline, fluoxetine, and paroxetine, can also elevate prolactin, though usually to a lesser degree. Beyond psychiatric medications, the list includes anti-nausea drugs like metoclopramide and domperidone, certain blood pressure medications, acid reflux drugs like ranitidine and cimetidine, opiates, estrogen-containing medications, and some anti-seizure drugs. If your prolactin came back high and you take any of these, your doctor will likely consider the medication as the explanation before looking further.
Pituitary Tumors (Prolactinomas)
A prolactinoma is a benign tumor of the pituitary gland that produces excess prolactin. These are the most common type of pituitary tumor, and despite the word “tumor,” they are almost never cancerous. They’re classified by size: microadenomas are 10 mm or smaller, while macroadenomas are larger than 10 mm.
Size generally tracks with how high prolactin goes. Macroadenomas typically push prolactin above 250 ng/mL, and levels above 500 ng/mL are considered diagnostic of a macroadenoma on their own. Microadenomas cause more modest elevations. If your prolactin is, say, 45 ng/mL, a giant pituitary tumor is unlikely. If it’s 800 ng/mL, a macroadenoma is almost certain.
One diagnostic quirk worth knowing: very large tumors can produce so much prolactin that the lab test actually misreads the result as low, a phenomenon called the “hook effect.” This is why doctors sometimes request a diluted sample when imaging shows a large pituitary mass but prolactin looks normal or only mildly elevated.
Thyroid Problems and Prolactin
An underactive thyroid (hypothyroidism) can raise prolactin through an indirect mechanism. When thyroid hormone levels are low, your brain compensates by producing more thyrotropin-releasing hormone (TRH) to try to stimulate the thyroid. TRH doesn’t just act on thyroid-stimulating cells in the pituitary; it also weakly stimulates the cells that produce prolactin. The result is a mild to moderate prolactin elevation that can mimic a prolactinoma, sometimes even causing the pituitary gland to enlarge visibly on an MRI.
This matters because the treatment is completely different. Rather than targeting prolactin directly, correcting the thyroid deficiency with thyroid hormone replacement brings prolactin back to normal on its own. A simple thyroid blood test can rule this in or out.
Symptoms in Women
The most recognizable signs of high prolactin in women are menstrual changes and unexpected breast milk production (galactorrhea). Periods may become irregular, unusually light, or stop entirely. Some women first discover they have high prolactin while being evaluated for infertility, since elevated prolactin suppresses ovulation. Galactorrhea can range from a few drops expressed with pressure to spontaneous leaking.
Over time, the estrogen suppression caused by high prolactin can also lead to vaginal dryness, reduced sex drive, and, if left untreated for years, loss of bone density similar to what happens after menopause. Not all of these symptoms appear in every case. Some women with mildly elevated prolactin have no noticeable symptoms at all.
Symptoms in Men
In men, high prolactin lowers testosterone and commonly causes loss of sex drive and erectile dysfunction. These are often the first and sometimes the only symptoms, which means prolactinomas in men tend to be diagnosed later, often after the tumor has grown large enough to cause headaches or vision changes from pressing on nearby structures. Reduced testosterone over time can also lead to decreased energy, loss of muscle mass, and reduced body hair. Breast enlargement and, rarely, breast discharge can occur.
Research suggests that the sexual effects of high prolactin in men aren’t purely hormonal. Studies have found that nighttime erections and physical arousal responses remain intact even when prolactin is high, pointing to a psychological or motivational component rather than a purely mechanical one.
How High Prolactin Is Diagnosed
Diagnosis starts with a blood test, but a single elevated result doesn’t always tell the whole story. Because prolactin fluctuates throughout the day and responds to stress, a mildly elevated reading is often repeated to confirm it’s consistent. Your doctor may ask you to avoid eating, exercising, or nipple stimulation before the repeat test, and may schedule the draw for a calm morning setting.
One important pitfall is macroprolactin, a form of prolactin that circulates bound to antibodies in a large molecular complex. Macroprolactin is biologically inactive, meaning it doesn’t cause symptoms, but standard lab tests can’t distinguish it from the active form. About 10% of samples that test high for prolactin may fall into a gray zone where macroprolactin is the main contributor. A follow-up test called PEG precipitation can clarify this. If the lab finds that most of the prolactin in your sample is this inactive form, you likely don’t need treatment at all.
When prolactin is confirmed to be genuinely and significantly elevated, an MRI of the pituitary is the next step to look for a tumor. Blood work for thyroid function, kidney function, and a pregnancy test (in women) helps rule out other causes.
Treatment Options
Treatment depends entirely on the cause. If a medication is responsible, switching to an alternative that doesn’t raise prolactin may be all that’s needed. If hypothyroidism is the culprit, thyroid hormone replacement resolves the problem. If stress or another transient factor caused the spike, no treatment is necessary.
For prolactinomas, the first-line treatment is medication, not surgery. Dopamine agonists work by mimicking dopamine’s natural ability to suppress prolactin release. The two main options are cabergoline (taken twice a week) and bromocriptine (taken daily). In a large head-to-head trial, cabergoline normalized prolactin in 83% of women compared to 59% with bromocriptine. Cabergoline also restored ovulation or led to pregnancy in 72% of cases versus 52% with bromocriptine, and caused fewer side effects, particularly less nausea and digestive discomfort. Only 3% of women on cabergoline stopped treatment due to side effects, compared to 12% on bromocriptine.
These medications don’t just lower prolactin. They also shrink the tumor itself in most cases, which is why surgery is typically reserved for the rare patients who don’t respond to medication or can’t tolerate it. Many people with microadenomas eventually try tapering off medication after a few years, and a significant portion find that their prolactin stays normal without it.