In toxicology , the median lethal dose , LD50 -LRB- abbreviation for `` Lethal Dose , NUMBER@1 % '' -RRB- , LC50 -LRB- Lethal Concentration , NUMBER@1 % -RRB- or LCt50 -LRB- ORGANIZATION@1 -RRB- of a toxic substance or radiation is the dose required to kill half the members of a tested population .

It is an abbreviation for `` Lethal Dose , NUMBER@1 % '' or median lethal dose .
