Serum selenium optimal range and reference range
Compiled by Alina Radu, founder of Sera, from the published sources below · Last reviewed November 9, 2026
Sera's bands for Serum selenium:
- Optimal 110 – 150 μg/L (110 – 150 ng/mL); sufficient 90 – 200 μg/L (90 – 200 ng/mL); out of range below 90 or above 200 μg/L.
Evidence grade: Published reference interval. A band that primarily reflects a published adult laboratory or population reference interval. It is not necessarily applicable to every assay or laboratory.
All units
| Unit | Optimal | Sufficient | Out of range |
|---|---|---|---|
| μg/L | 110 – 150 | 90 – 200 | below 90 or above 200 |
| ng/mL | 110 – 150 | 90 – 200 | below 90 or above 200 |
| μmol/L | 1.4 – 1.9 | 1.14 – 2.5 | below 1.14 or above 2.5 |
What the evidence says
The acceptable band of 90 to 200 µg/L follows the adult laboratory reference interval (Labcorp 93 to 198 µg/L); the NIH Office of Dietary Supplements regards 80 µg/L or higher as usually sufficient. The optimal band of 110 to 150 µg/L is a functional target: 110 is the lower limit of Mayo Clinic Laboratories' adult interval (110 to 165), and in a Swedish trial selenoprotein P was fully saturated at a serum selenium of 146 µg/L, so higher levels add no further selenoprotein. No outcome study sets 150 as a ceiling. Serum selenium reflects recent intake and falls with inflammation.
Assay: Results differ meaningfully between platforms and methods. Compare against the interval printed by the issuing laboratory before acting on a borderline value.
Sources
- Selenium, Serum or Plasma — Labcorp, 2026 · Laboratory / reference-interval sourceAdult (over 18 years) reference interval 93 to 198 µg/L for both sexes by ICP-MS; environmental exposure range 79 to 326 µg/L. Close to Sera's sufficient band of 90 to 200.
- Selenium, Serum — Mayo Clinic Laboratories, 2026 · Laboratory / reference-interval sourceNormal adult serum selenium 110 to 165 µg/L; in deficiency with loss of glutathione peroxidase activity the serum level is usually below 40 µg/L. The lower limit of 110 matches Sera's optimal lower edge.
- Selenium - Health Professional Fact Sheet — NIH Office of Dietary Supplements, 2025 · Government / public-health guidancePlasma or serum selenium of 8 µg/dL (80 µg/L) or higher is usually considered sufficient in healthy people. This sits 10 µg/L below Sera's sufficient lower edge of 90.
- Selenoprotein P increases upon selenium and coenzyme Q10 supplementation and is associated with telomere length, quality of life and reduced inflammation and mortality — Alehagen U, et al. — Free Radical Biology & Medicine, 2024 · Peer-reviewed publicationIn an elderly Swedish supplementation trial, selenoprotein P reached saturation at a serum selenium of 146 µg/L and glutathione peroxidase 3 at 99 µg/L. Close to Sera's optimal upper edge of 150; a biomarker plateau, not an outcome threshold.
What Selenium (Serum) measures
Serum or plasma selenium, the circulating fraction — distinct from the red cell compartment, which reflects a longer window.
Selenium is needed to convert thyroid hormone into its active form and to keep the immune system balanced. The serum value tracks intake over days to weeks and falls during an acute-phase response, so a low result alongside a raised CRP is worth repeating once the inflammation has settled.