Cholesterol is one of several fatty substances (lipids) found in the bloodstream. A person's total cholesterol is made up mainly of LDL-C and HDL- C. LDL-C is often called "bad" cholesterol because it can build up in the walls of the arteries and form plaque. Over time, the plaque can clog the arteries, resulting in a heart attack or stroke. HDL-C is often called "good" cholesterol because it helps keep LDL-C from building up in the arteries and because it protects against heart disease. Triglycerides are another form of fat in the blood, and may raise a person's risk of heart disease.