Answer
LDL is known as "bad" cholesterol because it becomes part of a plaque formation that could block arteries.
HDL is known as "good" cholesterol because it binds to cholesterol and carries the cholesterol to the liver to be removed from the body.
Work Step by Step
LDL and HDL are not actually types of cholesterol; they are cholesterol carriers called lipoproteins.
LDL is known as "bad" cholesterol because it can become part of a plaque formation that could block arteries and reduce or stop blood flow. This number should be less than 100 mg/dL in healthy people.
HDL is known as "good" cholesterol because it binds to extra cholesterol found in arteries and tissues, transporting this cholesterol to the liver to be removed from the body. In healthy people, this number should be greater than 40 or 50 mg/dL, depending on the person's sex.
