LD50 stands for "Lethal Dose 50%" and is a toxicological unit that measures the lethal dose of a given substance. It is the amount of a material, given all at once, which causes the death of 50% (one half) of a group of test animals. The LD50 is one way to measure the short-term poisoning potential (acute toxicity) of a material. The value of LD50 for a substance is the dose required to kill half the members of a tested population after a specified test duration. LD50 figures are frequently used as a general indicator of a substances acute toxicity, and a lower LD50 is indicative of increased toxicity. The LD50 test was neither designed nor intended to give information on long-term exposure effects of a chemical. Once you have an LD50 value, it can be compared to other values by using a toxicity scale. However, the LD50 is only one source of toxicity information, and for a more thorough picture of the immediate or acute toxicity of a chemical, additional information should be considered such as the lowest dose that causes a toxic effect (TDLO) .