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: Selenium, Serum or Plasma, Mass Concentration

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

: This test measures the amount of selenium in your blood serum or plasma. Selenium is an essential trace mineral that supports thyroid function, antioxidant defenses, and the immune system.

Quick summary

[": A selenium blood test helps check whether your body has enough of this important mineral to stay healthy."]

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

Key facts at a glance

LOINC
5724-0
Short code
Selenium SerPl-mCnc
Synonyms
Selenium SerPl-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

: What Is Selenium?

: Selenium is a trace mineral found in small amounts throughout the body. It is incorporated into proteins called selenoproteins, which help protect cells from damage and play a role in thyroid hormone metabolism and immune function.

: Why the Test Is Ordered

: Your healthcare provider may order this test if you have symptoms or risk factors suggesting too little or too much selenium. It can also be used to monitor people receiving nutritional support or those with conditions that affect nutrient absorption.

: How the Sample Is Collected

: A blood sample is drawn from a vein in your arm, usually into a tube that yields serum or plasma. The sample is then sent to a laboratory for analysis of selenium concentration.

: What the Results Mean

: Results are reported as a mass concentration and compared with the laboratory's reference interval. Levels below or above the expected range may prompt further evaluation, but results are interpreted alongside your symptoms, diet, and other tests. Your provider will explain what your specific result means for you.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

: Selenium status matters because both deficiency and excess can cause health problems. Low selenium has been linked to thyroid and immune concerns, while very high intake can be toxic. This test helps your care team assess whether your selenium level is in a healthy range.

Short name

: Selenium

Frequently asked questions

: Do I need to fast before a selenium blood test?
: Fasting is usually not required, but follow any instructions your provider or laboratory gives you, since other tests drawn at the same time may have preparation requirements.
: Can I get selenium from food instead of a supplement?
: Yes. Selenium occurs naturally in foods such as Brazil nuts, seafood, meat, eggs, and grains. Food sources are generally preferred, and your provider can advise whether a supplement is appropriate.
: Should I take selenium supplements on my own?
: It is best to talk with your healthcare provider before starting selenium supplements, because too much selenium can be harmful and supplement needs vary from person to person.
  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