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Sodium concentration in red blood cells (RBCs)

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

This test measures the amount of sodium inside red blood cells, which can help assess how well your body regulates fluids and electrolytes.

Quick summary

["Understanding RBC sodium levels helps diagnose conditions affecting fluid balance or red blood cell function."]

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

Key facts at a glance

LOINC
12907-2
Short code
Sodium RBC-sCnc
Synonyms
Sodium RBC-sCnc
Category
electrolyte
Sample
whole-blood
Container
Lavender-top (EDTA)
Units
N/A
Ref low
136
Ref high
145
Critical range
120 N/A – 160 N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
CPT
84295
SNOMED
110741000
Specimen volume
3 mL
Stability
Room temperature: 4h, Refrigerated: 24h
Hemolysis max
0
Lipemia max
0
Icterus max
0
TAT
4–24 hours
Order
routine

Why This Test Is Done

Doctors may order this test if you have symptoms like swelling (edema), high blood pressure, or unusual fatigue, which could indicate imbalances in how your body handles fluids or electrolytes. It may also be part of a broader evaluation for conditions like congestive heart failure, kidney disease, or certain metabolic disorders.

What to Expect Before the Test

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

What the Results Mean

Results show the sodium concentration inside red blood cells, but exact values may vary by lab. High or low RBC sodium levels can signal underlying health issues, such as abnormal fluid shifts or metabolic disorders.

Common Conditions Linked to RBC Sodium Levels

Elevated RBC sodium might suggest conditions like severe dehydration, certain kidney problems, or overuse of diuretics. Low RBC sodium could indicate fluid retention, hormonal imbalances, or other metabolic disturbances.

Reference range

Adult: 136-145 mmol/LN/A

Specimen: whole-blood

No special preparation required. Stay well hydrated.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

RBC Sodium Level

Frequently asked questions

What causes abnormal RBC sodium levels?
Abnormal RBC sodium levels can result from conditions affecting fluid balance (e.g., heart or kidney disease), hormonal imbalances (e.g., adrenal disorders), or medications that alter electrolyte levels. Your doctor will consider your symptoms, medical history, and other test results to determine the cause.
How do I prepare for follow-up testing if my RBC sodium level is abnormal?
If your RBC sodium level is outside the expected range, your doctor may recommend additional tests, such as blood pressure monitoring, kidney function checks, or hormone level assessments. They may also adjust medications or treatments based on the findings.
Can lifestyle changes help if my RBC sodium level is abnormal?
Yes, lifestyle adjustments like managing fluid intake, reducing salt, and addressing underlying conditions (e.g., heart failure) can sometimes help normalize RBC sodium levels. Always follow your doctor’s guidance for personalized advice.
  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