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M Protein, Urine — Electrophoresis, Without Concentration

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

A urine test that separates proteins to look for an M protein, an abnormal monoclonal protein sometimes associated with plasma-cell disorders.

Quick summary

["This urine electrophoresis test helps detect and characterize abnormal monoclonal proteins that may be released by plasma cells."]

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

Key facts at a glance

LOINC
39033-6
Short code
MR UE WO contr
Synonyms
MR UE WO contr
Category
liver
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
Method
mr
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?

Urine M-protein electrophoresis separates the different proteins in a urine sample so the laboratory can look for an M protein. An M protein is a single type of immunoglobulin produced by plasma cells; it may also be called a monoclonal protein or monoclonal band.

Why might I need this test?

This test may be ordered to evaluate protein in the urine, particularly when there are symptoms or laboratory findings that raise concern for a plasma-cell disorder such as multiple myeloma. It may also be used alongside blood and urine tests to investigate unexplained protein production or kidney-related findings.

How is the test performed?

A urine specimen is analyzed by electrophoresis, which separates proteins according to their properties. The laboratory then reviews the protein pattern for an abnormal monoclonal band. In this test version, the urine is analyzed without being concentrated.

How do I prepare for the test?

Collect urine exactly as your healthcare professional or laboratory instructs. Depending on the order, this may be a first-morning specimen or a timed collection. Tell the laboratory if you have a urinary tract infection, fever, or recently exercised intensely, because these can temporarily affect urine protein results.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

Urine M-protein electrophoresis

Frequently asked questions

Does an M-protein result mean I have multiple myeloma?
No. Finding an M protein supports further evaluation for a plasma-cell disorder but does not diagnose multiple myeloma by itself. Your clinician will interpret it with other blood, urine, imaging, and clinical findings.
Is this the same as a routine urinalysis?
No. A routine urinalysis checks several substances in urine, while electrophoresis separates urine proteins to identify their pattern and look for a monoclonal band.
Can this test be negative even when a plasma-cell disorder is suspected?
Yes. A monoclonal protein may not be present in the urine or may be too limited to detect. Negative results do not rule out a disorder, so follow-up testing may still be needed.
  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