Selenium
A trace mineral important for thyroid hormone metabolism and antioxidant defense.
| Typical reference range | 63–160 ug/L |
Ranges vary by laboratory, method, age and sex: always use the range printed on your own report. Why labs differ.
What it measures
Selenium is incorporated into selenoproteins, including glutathione peroxidases (antioxidant enzymes) and the deiodinases that convert T4 to T3. Brazil nuts, seafood, meat and eggs are major sources, and soil content varies by region.
Why it matters
Adequate selenium supports thyroid function, immune function and antioxidant defenses. Both deficiency and excess are harmful, with a relatively narrow optimal window.
What a high result can mean
High levels usually reflect over-supplementation or large intake of Brazil nuts; toxicity (selenosis) causes hair and nail loss, garlic breath, GI upset and nerve symptoms.
What a low result can mean
Low levels occur with low-selenium soils, malabsorption, long-term parenteral nutrition, dialysis and severe illness.
What affects the result
Serum reflects recent intake; whole blood reflects longer-term status, and ranges differ between sample types and labs (Labcorp ~93-198 ug/L). Avoid supplements before testing if a baseline is wanted.
Units and conversion
Usually reported in ug/L.
- From ng/mL: multiply by 1 to get ug/L
- From umol/L: multiply by 78.96 to get ug/L
- From ug/dL: multiply by 10 to get ug/L
Also called on lab reports
Selenium, Serum, Selenium, Blood, Se, Selenium, Plasma
Related tests: Vitamins & Nutrients
This page is educational and does not replace advice from a healthcare professional.