LD50 refers to the lethal dose for what percentage of the population?

LD50 refers to the lethal dose for what percentage of the population?

• A. 50 percent
• B. 25 percent
• C. 75 percent
• D. 100 percent

Answer: (A)

LD50 is the median lethal dose—the amount of a substance expected to kill 50% of a defined population under the same conditions (same species, route of exposure, and other factors). This value comes from a dose–response curve and is used to compare how potent different toxins are: a lower LD50 means a substance is more potent because a smaller dose can cause death in half the subjects. So the correct choice reflects the definition: 50 percent. The other percentages would correspond to other points on the curve (LD25, LD75, LD100) and are not the LD50. In practice, LD50 is often expressed as milligrams of substance per kilogram of body weight.

LD50 is the median lethal dose—the amount of a substance expected to kill 50% of a defined population under the same conditions (same species, route of exposure, and other factors). This value comes from a dose–response curve and is used to compare how potent different toxins are: a lower LD50 means a substance is more potent because a smaller dose can cause death in half the subjects. So the correct choice reflects the definition: 50 percent. The other percentages would correspond to other points on the curve (LD25, LD75, LD100) and are not the LD50. In practice, LD50 is often expressed as milligrams of substance per kilogram of body weight.