hypervitaminosis /-vī′təminō″sis/ , an abnormal condition resulting from excessive intake of toxic amounts (self-prescribed, usually from supplements) of one or more vitamins, especially over a long period. Serious effects may result from overdoses of fat-soluble vitamins A, D, E, or K, but adverse reactions are less likely with the water-soluble B and C vitamins, except when taken in megadoses. Compare avitaminosis. See also megadose, specific vitamins.
