Fractionated Plasma-Free Metanephrines

This is a test to help diagnose or rule out a pheochromocytoma (tumor of the adrenal gland). It may be done if you have symptoms of persistent or episodic high blood pressure such as severe headaches, rapid heart rate, and sweating.

The plasma free metanephrines test measures the amount of metanephrine and normetanephrine in the blood. These substances are metabolites (breakdown products) of epinephrine and norepinephrine. Epinephrine and norepinephrine are catecholamine hormones that help regulate the flow and pressure of blood throughout the body and play important roles in the body's response to stress. They are produced in the adrenal glands. Each person has two adrenal glands located on top of the kidneys. The catecholamines that the adrenal glands create, and their metabolites (metanephrine and normetanephrine), are normally found in small fluctuating quantities in both the blood and urine.


A blood sample is obtained by inserting a needle into a vein in your arm. Talk to your caregiver about your diet and any medications you are taking. You should discontinue epinephrine and epinephrine-like drugs for at least one week before the test, stop using acetaminophen 48 hours before, and fast (no food or liquids other than water) for about 8 to 10 hours prior to the test. It is especially important not to have any caffeine, coffee (including decaf), tobacco, tea, or alcohol for at least four hours before specimen collection.


Your caregiver will go over the test results with you and discuss the importance and meaning of your results, as well as treatment options and the need for additional tests if necessary.


It is your responsibility to obtain your test results. Ask the lab or department performing the test when and how you will get your results.