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Free Metanephrines/Creatinine Ratio, Serum/Plasma

Published: August 9, 2026Updated: August 16, 2026

A blood test that measures free metanephrines relative to creatinine. It helps evaluate possible excess catecholamine production.

Quick summary

["Elevated free metanephrines can suggest a catecholamine-producing tumor, but temporary and medication-related causes must also be considered."]

Medically reviewed by WellAlly Editorial TeamLast reviewed August 16, 2026Editorial policy

Key facts at a glance

LOINC
101177-4
Short code
Metaneph Free/Creat SerPl-sRto
Synonyms
Metaneph Free/Creat SerPl-sRto
Category
kidney
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
Specimen volume
5 mL
Stability
Room temperature: 4h, Refrigerated: 24h, Frozen: 7d
Hemolysis max
500
Lipemia max
1000
Icterus max
500
TAT
4–24 hours
Order
routine

What is this test?

This test measures free metanephrines, which are small substances produced by catecholamine-producing cells, in serum or plasma. Creatinine may be used as a comparison value to help interpret the metanephrine result.

Why might I need this test?

The test may be ordered when symptoms suggest an adrenal or nervous-system tumor that produces excess catecholamines. These may include episodic headaches, sweating, a fast heartbeat, tremor, or unexplained high blood pressure.

How is the test performed?

A blood sample is drawn from a vein and tested in a laboratory to determine the amount of free metanephrines. Collection conditions can affect results, so rest and timing instructions from the laboratory are important.

How do I prepare for the test?

Follow the laboratory's instructions exactly. Some clinicians recommend avoiding strenuous exercise, stress, caffeine, alcohol, and nicotine before collection, and they may request a resting period beforehand. Do not stop medications without medical guidance.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

Free metanephrines/creatinine

Frequently asked questions

What are metanephrines?
Metanephrines are small breakdown products of catecholamines such as epinephrine and norepinephrine. Their blood levels can help identify tumors that produce excess catecholamines.
Does an elevated result mean I have a tumor?
No. Elevated metanephrines can also result from stress, illness, exercise, or medication, and they do not confirm a tumor by themselves. Your clinician will interpret the result with your symptoms and may recommend repeat or confirmatory testing.
Should I stop medications before this test?
Do not stop prescribed medications without instructions from your clinician. Some drugs and supplements can affect the result, so tell the healthcare team and laboratory about everything you are taking.
  1. 1
    MedlinePlus — Laboratory TestsSource
  2. 2
    Lab Tests OnlineSource
  3. 3
    Mayo Clinic — Tests & ProceduresSource

Click any link to access the full source. PubMed Central (PMC) links provide free full-text access.

This information is for educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment.

Medical Disclaimer

This content is for general informational and educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Always seek the guidance of a qualified healthcare provider with any questions you have about a medical condition, and never disregard professional medical advice or delay seeking it because of something you read here.

If you think you may have a medical emergency, call your local emergency number or go to the nearest emergency department immediately.

Medically reviewed by WellAlly Editorial Team Last reviewed August 16, 2026. · Read our editorial policy