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Prolactin is a hormone made by the pituitary gland. Its main job is to produce milk after a baby is born. A high level can point to a condition of the pituitary gland, the thyroid or the kidneys. A low level is rare and can point to a condition of the pituitary gland.[1]
On this page you can read what prolactin is, what the guidelines say about a level that is too low or too high, what affects your level and which other levels are best read alongside it.
Also known as: PRL, PRL test, prolactin blood test. At the lab: PROL.
Prolactin is a hormone. It is made by the pituitary gland, a small gland at the base of your brain. Hormones are chemical messengers in your blood. They control how certain cells or organs work.[1]
Prolactin plays a role in many processes in your body. Its main job is to make breast tissue grow when someone is pregnant. After the birth, it drives the production of milk for the baby. That is why the level is high in people who are pregnant or have just given birth.[1]
In women who are not pregnant and in men, the level is normally low.[1]
A level that is too high can affect your body in different ways. In women, it can affect how the ovaries work. That can cause problems with periods and difficulty getting pregnant. In men, it can affect how the testicles work. That can lead to a lower sex drive and difficulty getting an erection.[1]
In people who are not pregnant or breastfeeding, a high level can make the body produce milk. The test does not show the cause of a high level. Your level does help your doctor choose which other tests are needed.[1]
The Endocrine Society has a guideline for doctors on a prolactin level that is too high. It sets out how a doctor looks for the cause, including when a medicine raises the level.[2]
The lab BioProfile works with, Labplusarts, uses a reference range of 4 to 23 µg/L for prolactin. The lab calls a level between those limits normal.[3]
| Value | What it can mean | Who it is for |
|---|---|---|
| Lower than normal[1] | Rare; can point to a condition of the pituitary gland | Men and women in general |
| Low[1] | Typical | Women who are not pregnant, and men |
| High[1] | Typical | Women who are pregnant or have just given birth |
| Slightly raised[1] | May be caused by stress, exercise or sex | Men and women in general |
| Higher than normal[1] | May point to a condition of the pituitary gland, the hypothalamus, the thyroid, the liver or the kidneys | Men and women who are not pregnant or breastfeeding |
Source: MedlinePlus, U.S. National Library of Medicine. A general explanation without figures. Your doctor also takes your symptoms, your sex and your medical history into account.[1]
A level that is too low is rare. It may point to a condition of the pituitary gland. With too little prolactin, a woman sometimes does not make enough milk for the baby after giving birth. Usually that is the only symptom.[1]
In people who are not pregnant or breastfeeding, a level that is too high may point to a condition of the pituitary gland or the hypothalamus. That is the part of the brain that controls the pituitary. It may also point to a condition of the thyroid, the liver or the kidneys, or in women, the ovaries. A high level does not always mean a condition. Your doctor may have your level measured again.[1]
BioProfile is working on its own zones for each value, from risk to optimal. A doctor reviews those zones before they appear in your result.
Your prolactin changes over the course of the day. That is why your blood is usually taken three to four hours after you get up. Sometimes your doctor asks you not to eat or drink for a few hours.[1]
Food high in protein can raise your level. Certain medicines and vitamins can also affect your level. So tell your doctor what you take.[1, 2]
Stress, exercise and sex can make your level rise slightly.[1]
A condition of the thyroid, the kidneys or the pituitary gland can raise your level. So can a wound to the chest. If you are pregnant or have just given birth, your level is naturally high.[1]
Prolactin is included in BioProfile 121 and 150.[4]
The BioProfile editorial team wrote this page on 10 October 2026 from the sources below, which we read on 10 October 2026. Every number on this page appears in one of those sources, with that source's number next to it. An expert has yet to check this page; after that check, the expert's name and the date of the check will appear at the top. This page offers explanation, not a diagnosis. Discuss a value outside the range with your GP.
