median lethal dose

(pharmacology) The dose of a substance which is fatal to 50% of the test animals. Abbreviated LD₅₀. Also known as median lethal dose.

One special form of the effective dose 50, or median effective dose. The lethal dose 50, or median lethal dose (LD₅₀), is used when the response that is being investigated is the death of the experimental animal. The median lethal dose is therefore the dose which is fatal to 50% of the test animals. See also Effective dose 50.

The amount of ionizing radiation required to kill, within a specified period, 50% of the individuals in a large group or population of animals or organisms.