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Selenium in Serum or Plasma (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—low levels may affect these processes."]

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

Key facts at a glance

LOINC
17574-5
Short code
Selenium Fld-mCnc
Synonyms
Selenium Fld-mCnc
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 Is This Test Done?

Your healthcare provider may order this test to check for selenium deficiency, monitor selenium levels in conditions like thyroid disorders, or assess exposure to selenium-containing medications or supplements.

What to Expect Before the Test

No special preparation is needed. You may have blood drawn from a vein in your arm, similar to other blood tests. If you’re on a selenium supplement, check with your provider first to avoid interfering results.

What the Results Mean

Results are compared to a general reference range for selenium in blood. Low levels may indicate poor absorption, certain medical conditions, or dietary deficiencies, while very high levels could signal over-supplementation or rare metabolic issues.

Common Reasons for Testing

This test is often used to evaluate selenium status in patients with chronic illnesses (e.g., autoimmune diseases), those on selenium-rich treatments, or those with suspected selenium deficiency symptoms like fatigue or hair loss.

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 seafood, nuts, or whole grains), certain medical conditions (e.g., malabsorption syndromes), or excessive use of selenium supplements.
How long does it take to get results?
Results are typically available within 1–3 business days, depending on your lab’s processing time. Your provider will discuss them with you during your follow-up visit.
Can diet affect selenium test results?
Yes, your recent diet may influence results. If you’re on a selenium-rich supplement or special diet, inform your provider before testing to avoid misleading results.
  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