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Selenium in Serum (Mass Concentration)

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

This test measures the amount of selenium, a trace mineral essential for thyroid function, immune health, and antioxidant protection, in your blood.

Quick summary

["Selenium helps support your body’s natural defenses and metabolism."]

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

Key facts at a glance

LOINC
20961-9
Short code
Selenium Feed-mCnt
Synonyms
Selenium Feed-mCnt
Category
chemistry
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
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

Why This Test Might Be Ordered

Your healthcare provider may recommend this test if you have symptoms like fatigue, hair loss, or muscle weakness, or if you have conditions like selenium deficiency or certain thyroid disorders. It may also be part of routine screening for those with chronic illnesses or dietary concerns.

What to Expect Before the Test

No special preparation is needed. You may have a small needle inserted into your arm to draw blood. If you’re anxious, let your provider know—they can offer comfort measures.

What the Results Mean

Results help assess whether your selenium levels are within a healthy range. Low levels may indicate deficiencies, while very high levels could signal potential toxicity or other health concerns.

Common Conditions Linked to Selenium Levels

Selenium is critical for thyroid hormones, immune function, and DNA repair. Abnormal levels may be associated with thyroid disorders, immune system issues, or certain genetic conditions.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

Selenium Level

Frequently asked questions

What causes selenium levels to be low?
Selenium deficiency can result from poor diet (low intake of selenium-rich foods like nuts, fish, or whole grains), certain medical conditions, or medications that interfere with absorption.
How long does it take to get results?
Results are typically available within 1–3 business days, depending on your lab’s processing time and your healthcare provider’s workflow.
Can I take supplements to raise my selenium levels?
If your provider suggests selenium supplements, they’ll recommend a safe dose. Overdosing can be harmful, so always follow their guidance.
  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