Than the median effective concentration (EC50 ) and the median effective dose ( ED50) is in Pharmacology and Toxicology, the effective concentration or dose refers to, in which a half-maximal effect is observed. The mean effective dose can not be measured directly but must be inferred from a given to a group of individuals dose -response curve by mathematical modeling.

When determining the toxicity EC50 dose, the effect triggers another defined as death in 50% of the tested population corresponds - in lethality would be called LD50.

In pharmacology is calculated by the ratio of LD50 and ED50 the Therapeutic width.