Prolactin
Pituitary hormone that mainly controls breast growth and milk production
Also known as
Definition
Prolactin is made in the pituitary gland. Its main job is to make breast tissue grow during pregnancy and to trigger milk production after birth, so levels are normally high in pregnant and breastfeeding women. In men and in women who are not pregnant, levels are low. Too much prolactin can affect the menstrual cycle and fertility in women, and sex drive and erections in men.
| Parameter | Value |
|---|---|
| Unit | ng/ml (µg/l), sometimes mU/l |
| Reference Range | Men: below 20 ng/ml; non-pregnant women: below 25 ng/ml; pregnant women: below 500 ng/ml. Labs differ; the range printed on your report is what counts, and your doctor interprets the result. |
Agree on your personal target range with your doctor.
1 ng/ml equals 1 µg/l. Some labs report prolactin in mU/l (µIU/ml); in that case only the reference range on your report applies.
↓ What a low value means
According to MedlinePlus, a prolactin level that is too low is rare and can be related to a pituitary disorder. Usually the only sign is that not enough milk is produced for breastfeeding after giving birth. Discuss any deviation with your doctor.
↑ What a high value means
A high prolactin level (hyperprolactinemia) can be related to a usually benign, prolactin-producing pituitary tumor (prolactinoma), which MedlinePlus names as the most common cause. Other possible links are other disorders of the pituitary or hypothalamus, an underactive thyroid, kidney or liver disease, PCOS, injury or irritation of the chest wall, and certain medicines, such as some antidepressants, estrogens, opioids or metoclopramide. Stress, high-protein meals, exercise, breast stimulation or sex can also raise the level slightly for a short time, so it is often measured again. Working this up is a job for your doctor, often an endocrinologist.
When to test
The test is usually ordered for irregular or missing periods, difficulty getting pregnant, milk discharge outside pregnancy and breastfeeding, low sex drive or erectile dysfunction, and to monitor a known prolactinoma. Prolactin varies over the day, so blood is usually drawn three to four hours after waking up, fasting if instructed. Mention all medicines and vitamins you take beforehand and do not stop anything without talking to your doctor.
Frequently asked questions
Why can exercise or sex shortly before the test change the result? +
According to MedlinePlus, physical exertion, sex, breast stimulation, stress and high-protein meals can raise prolactin slightly for a short time. A slightly raised value is therefore often repeated under standard conditions, for example early in the morning after eight hours of fasting.
Can medicines change prolactin levels? +
Yes. Some antidepressants, risperidone, estrogens, H2 blockers, metoclopramide, opioids and verapamil, among others, can raise the level, and according to MedlinePlus so can cannabis products. Tell your doctor what you take and do not stop anything on your own.
What is a prolactinoma? +
A prolactinoma is a benign pituitary tumor that makes prolactin. If it grows large, it can press on nearby structures and cause headaches or vision changes, for example. Whether a prolactinoma is present is clarified by further tests such as an MRI, not by the blood test alone.
Does prolactin matter for men too? +
Yes. A level that is too high can affect how the testicles work in men and can be related to low sex drive, erectile dysfunction, enlarged breasts or less body hair.
Prolactin
Sources
Last updated: October 05, 2026
This information is for orientation only and does not replace medical advice. Reference ranges can vary by laboratory, method and country.