Sodium hypochlorite, the active ingredient in household bleach, has a 50% chance of being lethal at a concentration of 192 mg per kilogram of a person's weight, according to a resource from Cornell University. That would equal about 3.6 grams of liquid bleach (at a concentration of 5.25%) per kilogram of the drinker's weight.
Bleach is also horribly caustic and causes soft tissue chemical burns on contact, especially if imbibed. Even consumed in small doses, a person becomes seriously ill and requires hospitalization, explains Cornell University. If a person suspects that he or another has consumed bleach, he should call the poison control center immediately.