How It Feels

The blood sample is taken from a vein in your arm. An elastic band is wrapped around your upper arm. It may feel tight. You may feel nothing at all from the needle, or you may feel a quick sting or pinch.

Risks

There is very little chance of a problem from having blood sample taken from a vein.

Risks of a blood test

• You may get a small bruise at the site. You can lower the chance of bruising by keeping pressure on the site for several minutes.
• In rare cases, the vein may become swollen after the blood sample is taken. This problem is called phlebitis. A warm compress can be used several times a day to treat this.
• Ongoing bleeding can be a problem for people with bleeding disorders. Aspirin, warfarin (Coumadin), and other blood-thinning medicines can make bleeding more likely. If you have bleeding or clotting problems, or if you take blood-thinning medicine, tell your doctor before your blood sample is taken.

Results

A prolactin test measures the level of the hormone prolactin, which is made by the pituitary gland, in your blood. Prolactin levels are different throughout the day. The highest levels occur during sleep and shortly after you wake up.

Normal

The normal values listed here-called a reference range-are just a guide. These ranges vary from lab to lab, and your lab may have a different range for what’s normal. Your lab report should contain the range your lab uses. Also, your doctor will evaluate your results based on your health and other factors. This means that a value that falls outside the normal values listed here may still be normal for you or your lab.

High values

• High levels of prolactin (usually higher than 200 ng/mL) may mean a pituitary gland tumor (prolactinoma) is present. The higher the prolactin level, the more likely a pituitary gland tumor is present. If a prolactin level is over 200 ng/mL, a magnetic resonance imaging (MRI) test may be done to confirm a pituitary tumor is present. A normal or low prolactin level does not always mean there is no pituitary tumor. An MRI test may be done if a pituitary tumor is suspected.
• High levels of prolactin may mean that the pituitary gland is making excess prolactin for unknown reasons (idiopathic hyperprolactinemia).
• Other conditions that can cause high prolactin levels include pregnancy, liver disease (cirrhosis), kidney disease, and hypothyroidism.

Many conditions can affect prolactin levels. Your health professional will talk with you about any abnormal results in relation to your symptoms and past health.