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Red Blood Cell Casts, Urine — Microscopy, Low-Power Field

Published: August 9, 2026Updated: August 17, 2026

Microscopic examination of urine for red blood cell casts, which can help evaluate bleeding or inflammation within the kidneys.

Quick summary

["Red blood cell casts in urine may suggest bleeding or inflammation originating in the kidneys."]

Medically reviewed by WellAlly Editorial TeamLast reviewed August 17, 2026Editorial policy

Key facts at a glance

LOINC
5807-3
Short code
RBC Casts #/area UrnS LPF
Synonyms
RBC Casts #/area UrnS LPF
Category
liver
Sample
urine
Container
Sterile urine container
Units
N/A
Ref low
10
Ref high
40
Critical range
2 N/A – 7 N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
Method
microscopy-light-lpf
CPT
84484
SNOMED
302774002
Specimen volume
10 mL
Stability
Room temperature: 2h, Refrigerated: 24h, Frozen: 7d
Hemolysis max
0
Lipemia max
0
Icterus max
0
TAT
4–24 hours
Order
routine

What is this test?

This test examines a urine sample under a microscope to look for red blood cell casts. These small structures form when red blood cells become trapped in proteins produced by the kidneys.

Why might I need this test?

Urine red blood cell casts may be checked when blood is found in the urine or when a clinician is evaluating kidney inflammation. They can also help distinguish bleeding within the kidneys from bleeding elsewhere in the urinary tract.

How is the test performed?

A urine sample is processed to concentrate the material called urine sediment. A laboratory professional then examines the sediment with a microscope and reports the number of red blood cell casts seen per low-power field.

How do I prepare for the test?

This is generally performed on a urine specimen collected using the clean-catch method. Follow the laboratory's collection instructions, use a sterile container, and deliver the sample promptly when requested.

Reference range

Adult: 10-40 U/LN/A

Specimen: urine

No special preparation required. Stay well hydrated.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

Urine RBC casts

Frequently asked questions

What does an RBC cast mean?
An RBC cast is a microscopic structure made of red blood cells and protein. Its presence can suggest bleeding or inflammation within the kidneys.
Does finding RBC casts confirm a kidney disease?
No. RBC casts can support several different kidney or blood-vessel conditions, so the result must be interpreted with other tests and clinical findings.
Are RBC casts different from blood in the urine?
Yes. Blood may come from many parts of the urinary tract, while red blood cell casts more specifically point toward the origin of bleeding within the kidneys.
  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 17, 2026. · Read our editorial policy