Merck Manual

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Selenium Toxicity


Larry E. Johnson

, MD, PhD, University of Arkansas for Medical Sciences

Last review/revision Dec 2021 | Modified Sep 2022
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Selenium (Se) is a part of the enzyme glutathione peroxidase, which metabolizes hydroperoxides formed from polyunsaturated fatty acids. Selenium is also a part of the enzymes that deiodinate thyroid hormones. Generally, selenium acts as an antioxidant that works with vitamin E.

Plasma levels of selenium vary from 8 to 25 mcg/dL (0.1 to 0.3 micromoles/L), depending on selenium intake.

At high doses (> 900 mcg/day), selenium causes toxicity.

Diagnosis of selenium toxicity is usually clinical; sometimes blood glutathione peroxidase is measured.

Manifestations include hair loss, abnormal nails, dermatitis, peripheral neuropathy, nausea, diarrhea, fatigue, irritability, and a garlic odor of the breath.

Toxic levels of plasma selenium are not well defined.

Treatment of selenium toxicity involves reducing selenium consumption.

Drugs Mentioned In This Article

Drug Name Select Trade
Alph-E-Mixed , AQUA-E, Aquasol E , Aquavite-E
No brand name available
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