You searched for: “lethal doses
lethal dose (s); LD; (noun), lethal doses (pl)
The amount of a toxic or poisonous substance that will cause a person to lose his or her life: The doctor said that Shelby's friend had died from a lethal dose of heroin which had been acquired from a street dealer.

Charlotte was warned by her doctor that there is such a thing as a lethal dose if she were to take too many sleeping pills.