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Selenium in Red Blood Cells (Mass Concentration)

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

This test measures the amount of selenium, an essential mineral, inside your red blood cells. Selenium plays a role in supporting immune function, antioxidant protection, and thyroid health.

Quick summary

["Selenium in red blood cells helps assess your body’s selenium status and overall antioxidant defenses."]

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

Key facts at a glance

LOINC
5723-2
Short code
Selenium RBC-mCnc
Synonyms
Selenium RBC-mCnc
Category
chemistry
Sample
whole-blood
Container
Lavender-top (EDTA)
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
CPT
85041
SNOMED
900000000000003001
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 Might Be Ordered

Your healthcare provider may recommend this test if you have symptoms of selenium deficiency (such as fatigue, hair loss, or muscle weakness) or if you’re at risk for selenium-related conditions. It may also be part of a broader evaluation for immune disorders, thyroid issues, or genetic conditions affecting selenium metabolism.

What to Expect Before the Test

No special preparation is needed for this test. A blood sample will be drawn from a vein in your arm, similar to other routine blood tests. The process usually takes a few minutes, and you may feel a slight pinch or discomfort.

What the Results Mean

Results help determine if your red blood cells contain adequate selenium levels. Low levels may indicate deficiency, while very high levels could suggest exposure to excessive selenium or certain medical conditions. Your provider will interpret results in the context of your overall health.

Common Reasons for Testing

This test is often used to evaluate selenium status in individuals with suspected deficiency, those undergoing treatment for selenium-related disorders, or as part of a nutritional assessment. It can also be useful in monitoring patients with genetic disorders linked to selenium metabolism.

Reference range

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

Red Blood Cell Selenium Level

Frequently asked questions

What does selenium do in the body?
Selenium is a vital mineral that supports immune function, helps protect cells from oxidative damage, and plays a role in thyroid hormone production. It’s also involved in maintaining healthy skin, hair, and nails. Low levels may contribute to fatigue, weakened immunity, or thyroid problems, while excess can sometimes cause toxicity symptoms like hair loss or nerve issues.
How is selenium deficiency diagnosed?
Deficiency is typically diagnosed through blood tests measuring selenium levels in red blood cells, serum, or other tissues. Symptoms like muscle weakness, hair loss, or immune dysfunction may prompt testing, but blood tests are the most reliable way to confirm low selenium levels.
Can diet affect selenium levels?
Yes, diet plays a major role. Selenium is found in foods like seafood, nuts, whole grains, and meat. Certain diets (e.g., vegan diets) may require monitoring to ensure adequate intake, as selenium sources vary widely among foods.
  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