Definition - What does LD50 mean?
LD50 is an acronym which stands for Lethal Dose 50. It is a measure of the amount of a substance that is needed to kill half of a test population of animals. It is used to measure the acute toxicity of substances, and this type of testing is normally performed with rates and mice. The LD50 level is stated as the number of milligrams that is administered for every 100 grams on small animals and per kilogram for larger animals.
Safeopedia explains LD50
The LD50 level is not to be confused with the LC50, which is the Lethal Concentration 50. This refers to the concentration of a substance in air (or in water) that is required to kill 50% of a test population of animals. These two measurements provide a reliable way to compare chemicals with different toxicities by measuring the same effect of each chemical.