What plasma/serum selenium concentration is considered adequate?

• A. 100 mcg/L
• B. 50 mcg/L
• C. 150 mcg/L
• D. 200 mcg/L

Answer: (A)

Maintaining enough selenium in plasma supports the activity of selenoproteins, especially glutathione peroxidase, which rely on selenium to protect cells from oxidative damage. Plasma selenium reflects overall status and helps guide PN supplementation. An adequate target is about 100 mcg/L, a level within the range where selenoprotein function is optimized without unnecessary excess. A value around 50 mcg/L suggests deficiency and impaired antioxidant defense, while 150–200 mcg/L is above the typical target and does not provide added benefit and may raise concerns if sustained.