How Do You Diagnose a Pheochromocytoma of the Adrenal Gland?
The diagnosis of pheochromocytoma is made by showing that the level of metanephrines in a patient's blood or urine is higher than it should be. Metanephrines (metanephrine and normetanephrine) are made continuously inside the tumor from the adrenaline-type hormones, which is why they are a more reliable test than measuring adrenaline itself. A clearly elevated level, together with an adrenal tumor on a scan, makes the diagnosis of pheochromocytoma. (Pheochromocytoma is the name for adrenaline-producing tumors of the adrenal medulla; the same hormones made by a tumor outside the adrenal gland mean a paraganglioma.) Mild elevations are common and are often caused by medications, stress or the way the blood was drawn, so they need to be repeated and interpreted carefully.What are the Tests Used to Diagnose a Pheochromocytoma of the Adrenal Gland?
First things first: the diagnosis of pheochromocytoma hinges on the treating physician considering the diagnosis in the first place. We can't diagnose a pheo if the doctor doesn't think of it, and this is the number one reason that many pheochromocytomas do not get diagnosed. Today many pheochromocytomas are found the other way around: an adrenal mass is seen on a scan done for another reason, and the blood test follows. Every adrenal mass should be tested. One of the following two tests is used:- Measurement of "plasma free metanephrines" (metanephrine and normetanephrine) in the blood. This is a test that the doctor orders, and it is done on a single tube of blood. It is a very sensitive test: a normal result makes a pheochromocytoma very unlikely. The blood is ideally drawn after you have been lying down and resting for 20–30 minutes, because a sample taken sitting up or under stress is more likely to be falsely high. A level more than about 3 times the upper limit of normal almost always indicates a pheochromocytoma or paraganglioma.
- Measurement of "urine fractionated metanephrines" in a 24-hour urine sample. The patient collects all of their urine for 24 hours (in a jug that the lab gives you), and then takes the jug back to the lab. This is also an accurate test and can be used instead of the blood test or to confirm it.
It is important to know that many medications may affect (increase) the test results, so tell us and your doctor what medications (if any) you were taking while being tested. Do not stop a prescribed medication without asking your doctor.
This list shows some of the medications and substances that may interfere with the measurement of metanephrines:
- Tricyclic antidepressants (including cyclobenzaprine)
- Levodopa
- Buspirone and antipsychotic agents
- Serotonin and noradrenaline reuptake inhibitors
- Monoamine oxidase inhibitors
- Drugs containing adrenergic receptor agonists (e.g., decongestants)
- Amphetamines and other stimulants
- Prochlorperazine
- Withdrawal from clonidine or alcohol
- Illicit drugs (e.g., cocaine)
Once it has been established that the metanephrines are elevated, a scan is used to locate the tumor, usually a CT or an MRI. Scans for pheochromocytoma and paraganglioma are discussed on our pheochromocytoma scans page. A suspected pheochromocytoma should not be biopsied with a needle.
Genetic testing. About 30–40% of pheochromocytomas and paragangliomas are hereditary, so genetic testing and counseling should be offered to every patient, whatever their age or family history. The result can change the operation that is planned and the follow-up, and it matters for family members. Learn more on our pheochromocytoma genetics page.
IMPORTANT: If you have a pheochromocytoma or paraganglioma, you need to be prepared for surgery. Most patients are treated with blood-pressure medication (alpha-blockers such as doxazosin or phenoxybenzamine, sometimes other medicines) and good hydration, usually for 1-2 weeks before the operation; the plan is individualized by the team. This applies even to “silent” pheochromocytomas with normal blood pressure. Read more about surgery for pheochromocytoma.
Read more about symptoms of pheochromocytoma on our adrenal surgery blog
Last updated October 2026.