An index of toxicity, the amount of the substance that kills 50% of the test population of experimental animals when administered as a single dose.
The dose of a drag that will cause death. For example, an LD50 signifies a dose that will kill 50% of the test subjects, therapeutic index.
The dose required to kill half the members of a tested population. Also called LC 50 (median lethal concentration).
The amount of a drug or other substance which will kill the person who takes it.