[The median lethal dose. the dose of a chemical or biologic preparation (e.g., a bacterial exotoxin or a suspension of bacteria) that is likely to cause death in 50% of the animals being tested; it varies in relation to the type of animal and the route of administration; (the absolute lethal dose is LD100, and minimal lethal dose is LD05). ( NCI )] (UMLS (NCI) C0023378) =Quantitative Concept