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Red Blood Cell Size Variability (Auto) Analysis

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

This test measures how much the size of your red blood cells varies, which can help identify certain blood conditions.

Quick summary

["Variability in red blood cell size may signal underlying health concerns like anemia or blood disorders."]

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

Key facts at a glance

LOINC
796-3
Short code
RBC # Snv Auto
Synonyms
RBC # Snv Auto
Category
chemistry
Sample
fluid
Container
Sterile tube
Units
N/A
Ref low
4.2
Ref high
5.9
Critical range
2 N/A – 7 N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
Method
automated-count
CPT
85041
SNOMED
900000000000003001
Specimen volume
2-5 mL
Stability
Room temperature: 2h, Refrigerated: 24h
Hemolysis max
300
TAT
4–24 hours
Order
routine

Why This Test Is Done

Your doctor may order this test if they suspect conditions like anemia (low red blood cells), iron deficiency, or other blood disorders. It helps assess whether red blood cells are consistently the same size or if there’s unusual variation, which can indicate problems with production or function.

What to Expect Before the Test

No special preparation is needed. You’ll provide a simple blood sample, usually drawn from a vein in your arm. The test is quick and typically done in a lab setting.

How the Test Works

The test analyzes the size (called *mean corpuscular volume*, or MCV) of your red blood cells to determine how much they differ from each other. Advanced technology automatically measures and compares cell sizes to generate a variability score.

Possible Results and Next Steps

If results show normal variability, no further action is needed. If high variability is detected, your doctor may recommend additional tests (like iron studies or blood counts) to investigate potential causes, such as nutritional deficiencies or chronic illnesses.

Reference range

Adult males: 4.2-5.9; Females: 3.8-5.1 x 10^12/LN/A

Specimen: fluid

No special preparation required. Stay well hydrated.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

Red Blood Cell Size Variability Test

Frequently asked questions

What causes red blood cell size variability to be tested?
Your doctor may order this test if you have symptoms like fatigue, pale skin, or unusual tiredness, or if they suspect conditions like anemia, iron deficiency, or other blood disorders.
Does this test require fasting?
No, fasting is not required for this test. You can eat and drink normally before the blood draw.
How long does it take to get results?
Results are typically available within a few days to a week, depending on your lab’s processing time.
  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