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Quick take
- What it measures: A metanephrines blood test measures plasma free metanephrine and normetanephrine, breakdown products of the stress hormones epinephrine and norepinephrine.
- Why it is ordered: It is mainly used to help detect or rule out rare catecholamine-producing tumors called pheochromocytomas and paragangliomas.
- Preparation matters: Stress, exercise, caffeine, nicotine, alcohol, certain medicines, and whether you are seated or lying down can affect results. Many labs prefer the sample be collected after resting while lying down.
- Normal results are reassuring: When collected and interpreted correctly, normal plasma free metanephrines make a catecholamine-secreting pheochromocytoma or paraganglioma unlikely in many patients.
- Mild elevations are not a diagnosis: Borderline or modestly high values often need repeat testing under controlled conditions or a 24-hour urine metanephrines test before imaging or treatment decisions.
What is a metanephrines blood test?
The metanephrines blood test, often listed on lab reports as plasma free metanephrines or fractionated free metanephrines, plasma, measures two small molecules in your blood: metanephrine and normetanephrine. These are metabolites, or breakdown products, of catecholamines—hormones made by the adrenal glands and certain nerve tissues that help regulate blood pressure, heart rate, and the body’s stress response.
The two main analytes usually reported are:
- Metanephrine: primarily related to epinephrine, also called adrenaline.
- Normetanephrine: primarily related to norepinephrine, also called noradrenaline.
This test is not a general “stress level” test. Clinically, it is most often used when a health professional wants to evaluate for a rare tumor that produces catecholamines, especially pheochromocytoma, which usually arises in the adrenal gland, or paraganglioma, which arises from related nerve tissue outside the adrenal gland. These tumors are often abbreviated together as PPGL.
Major endocrine guidance recommends that initial biochemical testing for suspected pheochromocytoma or paraganglioma include either plasma free metanephrines or urinary fractionated metanephrines. ARUP Consult similarly describes plasma or urine metanephrines as the recommended first biochemical step for suspected PPGL evaluation and emphasizes that collection conditions strongly influence plasma results.
Why a clinician may order plasma free metanephrines
A metanephrines blood test is usually ordered because symptoms, imaging, family history, or a known genetic risk raise the question of excess catecholamine production. The classic pattern associated with pheochromocytoma or paraganglioma is episodic high blood pressure with spells of headache, sweating, and palpitations, but real-world presentations vary. Some people have sustained hypertension, anxiety-like attacks, tremor, pallor, chest discomfort, or no obvious symptoms at all.
Common reasons for ordering the test include:
- Spells suggestive of catecholamine surges: episodes of pounding heartbeat, severe headache, sweating, shakiness, or sudden high blood pressure.
- Difficult-to-control or unusual hypertension: especially if blood pressure spikes are dramatic, occur at a young age, or do not fit the usual pattern of primary hypertension.
- An adrenal incidentaloma: an adrenal mass found on imaging done for another reason may need hormone evaluation, including testing for catecholamine excess.
- Known hereditary risk: certain inherited syndromes increase the risk of pheochromocytoma or paraganglioma.
- Follow-up after prior PPGL treatment: some patients need ongoing surveillance, usually directed by endocrinology or oncology specialists.
The test is not meant to diagnose common anxiety, panic disorder, essential hypertension, or dysautonomia by itself. Those conditions can produce overlapping symptoms, and some can also affect catecholamine-related labs. That is why interpretation depends heavily on your symptoms, blood pressure pattern, medications, collection conditions, and the degree of elevation.
How to prepare for a metanephrines blood test
Preparation is unusually important for this test because metanephrine and normetanephrine levels can rise when the sympathetic nervous system is activated. Exercise, pain, anxiety, acute illness, withdrawal from certain substances, stimulants, nicotine, and even sitting upright before the draw can contribute to higher values. The goal is not to “game” the test; it is to avoid preventable false alarms.
Ask for the exact instructions from the ordering clinician or lab
Preparation instructions vary by laboratory method and by the reason for testing. For example, some laboratories specify fasting, some specify avoidance of certain foods or substances, and many emphasize resting while lying down before the sample is drawn. Mayo Clinic Laboratories notes that substances increasing endogenous catecholamine levels can cause borderline elevations, and ARUP Consult recommends controlled collection conditions—fasting, supine rest, calm and warm surroundings—when a possible false-positive plasma result is being evaluated.
Common preparation points
| Preparation issue | Why it matters | Practical tip |
|---|---|---|
| Position before blood draw | Metanephrine values, especially normetanephrine, can be higher after sitting or standing because sympathetic activity changes with posture. | Ask whether the draw site can collect the sample after you rest lying down. Some protocols require 20–30 minutes of supine rest. |
| Exercise | Vigorous activity can raise catecholamine-related markers. | Avoid strenuous exercise before the test if your clinician or lab instructs you to do so. |
| Caffeine, nicotine, and alcohol | These can influence catecholamine release or sympathetic tone. | Follow the lab’s timing instructions; do not assume “a little” is harmless for this particular test. |
| Medications and supplements | Some antidepressants, stimulants, decongestants, blood pressure medicines, anesthetic agents, and withdrawal states can affect results. | Do not stop prescribed medication on your own. Ask the ordering clinician what to continue, pause, or document. |
| Stress, pain, and acute illness | Sympathetic activation can produce borderline elevations unrelated to a tumor. | If you are acutely ill, in severe pain, or had a very stressful event, ask whether testing should be rescheduled. |
| Fasting | Some protocols require fasting to reduce variability and avoid dietary confounding. | Confirm whether water is allowed and how long to fast. |
General lab-preparation advice from MedlinePlus also applies: understand the instructions before the day of the test, ask about food, drink, exercise, and medicines, and tell the lab or clinician if you could not follow the preparation steps exactly.
Important: do not stop medicines without medical guidance
Several medicines can influence catecholamine or metanephrine results, but stopping some drugs abruptly can be unsafe. This is especially true for blood pressure medicines, antidepressants, sedatives, opioids, and clonidine. If a medication could affect your result, your clinician may choose to interpret the result in that context, repeat the test later, or use a different testing strategy.
What happens during the blood draw?
The sample is usually drawn from a vein in your arm into a special tube, commonly plasma EDTA. Depending on the lab protocol, you may be asked to rest quietly before the draw, often lying flat. This is one of the most important details to clarify before arriving. Not every patient-service center can accommodate a prolonged supine rest period, and a seated draw may increase the chance of a borderline abnormal result.
After collection, the specimen often needs careful handling, such as prompt processing and separation of plasma. For example, reference laboratories may specify particular tubes and processing times because pre-analytic handling can affect specimen quality. You do not need to manage those technical steps yourself, but it helps to use a collection site familiar with plasma metanephrines.
The blood draw itself is brief. You may feel a pinch, mild bruising, or soreness at the puncture site. Serious complications are uncommon. If you have a history of fainting during blood draws, tell the phlebotomist before collection.
How to interpret metanephrines blood test results
Your result should be interpreted using the reference interval printed on your own lab report. Reference ranges can differ by method, age, sex, body position during collection, and laboratory. Do not compare your number directly with a range from another website or another lab unless your clinician says the methods are comparable.
Most reports show metanephrine and normetanephrine separately. Some may also include a total or interpretive comment. The pattern matters: isolated, tiny normetanephrine elevations are handled differently from marked elevations of both analytes in a patient with classic symptoms.
| Result pattern | What it often means | Common next step |
|---|---|---|
| Both metanephrine and normetanephrine within range | Usually reassuring, especially when the sample was collected correctly and clinical suspicion is low to moderate. | Your clinician may look for other explanations for symptoms or hypertension. |
| Mild or borderline elevation of one analyte | Often caused by collection posture, stress, medications, stimulants, exercise, illness, or other non-tumor factors. | Repeat plasma testing under controlled conditions or use 24-hour urine fractionated metanephrines. |
| More than about 2 times the upper reference limit, or more than one analyte elevated | Raises concern more than a borderline result, but still needs clinical correlation and sometimes confirmation. | Endocrinology evaluation; possible confirmatory biochemical testing and imaging if appropriate. |
| Marked elevation, especially more than about 3 times the upper reference limit | Much more suspicious for pheochromocytoma or paraganglioma, particularly with compatible symptoms or an adrenal mass. | Prompt specialist-directed evaluation, often including imaging after biochemical confirmation. |
ARUP Consult notes that plasma metanephrine results more than twice the upper limit, or elevated results for more than one analyte, may warrant imaging depending on context, while results greater than three times the upper reference limit are considered highly concerning in appropriate settings. Mayo Clinic Laboratories similarly emphasizes that normal plasma metanephrine and normetanephrine levels make pheochromocytoma or paraganglioma very unlikely for many patients, while elevated results often require a second testing strategy because the tumors are rare and false positives can occur.
What “free” and “fractionated” mean
Free metanephrines are the unbound forms circulating in plasma. Fractionated means the lab measures metanephrine and normetanephrine separately instead of reporting only a combined total. This separation is clinically useful because different tumor types and genetic syndromes can produce different biochemical patterns.
Does a high result mean cancer?
No. A high metanephrines blood test does not automatically mean cancer, and many pheochromocytomas are not metastatic. The test is a biochemical signal that must be interpreted carefully. Mild elevations are common enough that repeating the test under better conditions or confirming with urine testing is often the safest next step.
False positives, false negatives, and test limitations
The metanephrines blood test is powerful because many catecholamine-producing tumors continuously metabolize catecholamines into metanephrines, even when hormone release is episodic. That makes metanephrines more useful than catecholamines alone for many patients. However, no lab test is perfect.
False-positive results
A false positive means the test is elevated even though there is no pheochromocytoma or paraganglioma. This is one of the biggest practical issues with plasma metanephrines, especially when the elevation is small. Potential contributors include:
- Blood drawn while seated or soon after walking into the lab.
- Stress, anxiety, pain, acute illness, or poor sleep.
- Recent vigorous exercise.
- Caffeine, nicotine, alcohol, or stimulant use.
- Certain antidepressants, decongestants, stimulants, cocaine or related drugs, some anesthetics, and withdrawal from alcohol, benzodiazepines, opioids, or clonidine.
- Chronic kidney disease or other medical conditions that alter metabolism or clearance.
This is why borderline results are commonly repeated. A repeat sample collected after fasting, quiet supine rest, and avoidance of known triggers may normalize. If the collection site cannot provide the needed conditions, a 24-hour urine fractionated metanephrines test may be a better follow-up option.
False-negative results
False negatives are less common but possible. A very small tumor, certain tumor types, nonsecreting tumors, testing at the wrong time in a high-risk situation, or medication effects can complicate interpretation. If clinical suspicion remains high—such as a suspicious adrenal mass, strong hereditary risk, or classic severe episodes—your clinician may order repeat plasma testing, urine testing, catecholamines, genetic evaluation, or imaging even if one test is normal.
Why imaging usually comes after biochemical testing
For suspected PPGL, biochemical confirmation typically comes before CT, MRI, or nuclear medicine imaging unless there is an urgent clinical reason. Imaging can find incidental adrenal nodules that are unrelated to symptoms, and scanning too early may lead to unnecessary worry or procedures. Your clinician’s goal is to match the biochemical signal with the right imaging strategy.
Metanephrines blood test vs. 24-hour urine metanephrines
Both plasma free metanephrines and 24-hour urine fractionated metanephrines are accepted first-line biochemical tests for suspected pheochromocytoma or paraganglioma. The better choice depends on the patient, the reason for testing, the collection conditions available, and the clinician’s estimate of risk.
| Feature | Blood: plasma free metanephrines | Urine: 24-hour fractionated metanephrines |
|---|---|---|
| Convenience | One blood draw, but may require lying down quietly before collection. | Requires collecting all urine for 24 hours, which can be inconvenient. |
| Best use | Often preferred when clinical suspicion is higher or when a sensitive rule-out test is needed. | Often useful as a first test in lower-suspicion cases or as confirmation after mild plasma elevations. |
| Main limitation | More vulnerable to posture, stress, and sympathetic activation if collection is not controlled. | Accuracy depends on complete 24-hour collection and proper storage; kidney disease may affect usefulness. |
| Follow-up role | Can be repeated under controlled conditions after a borderline result. | Can help confirm or refute a mildly abnormal plasma test. |
Mayo Clinic Laboratories describes plasma free metanephrines as a highly sensitive test for excluding pheochromocytoma, while its 24-hour urine metanephrines information notes that urine testing can be used as a confirmatory study after less than two-fold plasma elevations. In practice, endocrinologists often choose based on the exact clinical scenario rather than treating one option as universally “best.”
How much does a metanephrines blood test cost?
The cost to the patient of a metanephrines blood test varies widely because the final amount depends on where the order originates, where the specimen is collected, which reference lab performs the test, insurance coverage, and whether any separate visit, draw, handling, or physician-ordering fees apply.
For insurance billing, the lab charge may be very different from the negotiated allowed amount. Medicare’s Clinical Laboratory Fee Schedule lists payment amounts for covered clinical lab tests, but a Medicare fee schedule amount is not the same as a hospital chargemaster price, a commercial insurance allowed amount, or a self-pay direct-access price. CMS also notes that listing a code or payment amount does not itself guarantee coverage for a specific patient or situation.
What to compare if paying cash
If you are paying out of pocket, compare the effective total cost, not just the advertised test price. The total may include:
- the metanephrines test price;
- a blood draw or specimen collection fee;
- a physician order or telehealth review fee if required;
- processing, handling, or reference-lab fees;
- repeat testing if the first sample is drawn under non-ideal conditions;
- follow-up visit costs to interpret abnormal results.
Also ask whether the collection site can follow the required posture and rest instructions. A low advertised price is less useful if the site cannot collect the specimen under conditions your clinician wants, because an avoidable borderline result can lead to repeat testing and more cost.
Insurance and medical necessity
Insurers may require documentation of medical necessity, such as symptoms, adrenal imaging findings, resistant hypertension, or hereditary risk. If your clinician orders the test, ask whether prior authorization is needed and whether the lab is in network. If you use a direct-access service, confirm whether results can be shared with your clinician and whether abnormal results include any medical review.
Practical next steps after results
The right next step depends on the result pattern and the reason the test was ordered.
If your results are normal
Normal plasma free metanephrines are usually reassuring, especially if the sample was collected properly and you are not in a high-risk group. Your clinician may focus on other causes of symptoms or hypertension, such as thyroid disease, primary hypertension, medication effects, sleep apnea, panic disorder, arrhythmia, or other endocrine conditions.
If your results are mildly elevated
Ask your clinician whether the collection conditions were optimal. Helpful questions include: Was I fasting? Was I lying down for the required rest period? Had I used caffeine, nicotine, stimulants, or decongestants? Was I in pain, acutely ill, or very anxious? Did any medicines need to be considered? Mild elevations often lead to repeat plasma testing under stricter conditions or a 24-hour urine test.
If your results are clearly high
Markedly elevated metanephrine or normetanephrine values deserve timely medical follow-up. Your clinician may refer you to an endocrinologist, confirm results with additional biochemical testing, review medications and family history, and then order imaging. Do not start intense exercise programs, change blood pressure medicines, or stop medications abruptly while awaiting evaluation unless a clinician gives specific instructions.
If you have severe symptoms
Seek urgent medical care for severe chest pain, fainting, stroke-like symptoms, severe shortness of breath, or dangerously high blood pressure with symptoms. Lab testing is not a substitute for emergency evaluation when symptoms are acute or severe.
FAQs about the metanephrines blood test
What does the metanephrines blood test show?
It shows the amount of free metanephrine and normetanephrine in plasma. These are breakdown products of epinephrine and norepinephrine. The test is mainly used to evaluate for catecholamine-producing tumors such as pheochromocytoma and paraganglioma.
Do I need to fast?
Many protocols prefer fasting, but instructions vary by lab and clinical situation. Follow the directions from your ordering clinician or laboratory. If you accidentally ate or drank something other than water, tell the collection site and ordering clinician so the result can be interpreted appropriately.
Why do some labs ask me to lie down before the blood draw?
Posture affects sympathetic nervous system activity. Sitting or standing before the draw can raise normetanephrine and increase the chance of a borderline false-positive result. Many protocols call for quiet rest while lying down before and during collection.
Can caffeine affect metanephrines?
Yes, caffeine can affect catecholamine-related physiology and may contribute to misleading results in some circumstances. Your lab may ask you to avoid caffeine for a specific time before testing.
Can medications affect the result?
Yes. Some antidepressants, stimulants, decongestants, blood pressure medicines, anesthetics, and withdrawal states can affect results. Do not stop prescribed medication unless the ordering clinician specifically tells you to do so.
Is a high metanephrine result always a pheochromocytoma?
No. Mild or borderline elevations are often due to collection conditions, stress, medicines, nicotine, caffeine, exercise, or other medical issues. Higher elevations, especially more than about three times the upper reference limit, are more concerning and usually need specialist follow-up.
Which is better: blood or urine metanephrines?
Both are useful. Plasma free metanephrines are often chosen when a sensitive rule-out test is needed, while 24-hour urine fractionated metanephrines can be useful in lower-suspicion situations or to confirm mild plasma elevations. The best choice depends on your clinical context and whether proper blood collection conditions are available.
How long do results take?
Turnaround time varies by lab. Because plasma metanephrines are often performed by specialized methods such as LC-MS/MS and may be sent to a reference lab, results may take longer than routine blood tests. Ask the ordering office or collection lab for their expected timeframe.
Can I order this test myself?
Availability depends on your state, the laboratory network, and whether a provider order is required. Even when direct ordering is available, abnormal results should be reviewed with a qualified clinician because interpretation can be complex and may require repeat testing or imaging decisions.
Sources
- Endocrine Society Clinical Practice Guideline: Pheochromocytoma and Paraganglioma
- ARUP Consult: Pheochromocytoma – Paraganglioma
- Mayo Clinic Laboratories: Metanephrines, Fractionated, Free, Plasma
- Mayo Clinic Laboratories: Metanephrines, Fractionated, 24 Hour, Urine
- MedlinePlus: Catecholamine Tests
- MedlinePlus: How to Prepare for a Lab Test
- Centers for Medicare & Medicaid Services: Clinical Laboratory Fee Schedule
