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Definition of Excess selenium
Medically reviewed by Min Clinic Staff | Updated: January 2026
Excess selenium: Too much selenium (selenosis) which may cause reversible balding and brittle nails, give a garlic odor to the breath, and cause intestinal distress, weakness and slowed mental functioning. People who chronically consume more than the tolerable upper intake level (UL) of selenium -- in adults, the UL is 400 micrograms per day of selenium -- are at risk for developing selenosis.