Selenium - blood, plasma

There is significant variability in different countries and regions depending on dietary selenium.

Plasma: 0.75-1.35 µmol/L
Blood: 1.1-2.5 µmol/L

In humans significant selenium deficiency is manifest primarily as cardiomyopathy. This correlates poorly with plasma selenium levels and rarely occurs in selenium deficient patients on total parenteral nutrition.

Keshan disease, a cardio­myopathy in the low-selenium Keshan region of China, and Kashin-Beck disease, a destructive bone and joint disease in parts of China and Siberia, are related to selenium deficiency. The presence of iodine and selenium deficiency is associated with endemic cretinism in China and Africa.

Selenium toxicity is common in herbivores in seleniferous regions, but occurs in humans only after ingestion of selenium as a chemical, rather than from a high dietary intake.