High-density lipoproteins, often called "good" cholesterol, carry excess cholesterol from the blood to the liver, according to Mayo Clinic. In contrast, low-density lipoproteins are considered "bad" cholesterol because they contribute to the formation of plaque. The American Heart Association defines plaque as a thick deposit that can clog the arteries.
Cholesterol is necessary for human survival because it is used to manufacture hormones, insulate nerves and form new cells. The liver produces the right amount of cholesterol for these functions, but people also take in extra cholesterol from the foods and beverages they consume. If there is too much cholesterol in the blood, it can reduce blood flow to the heart, according to WebMD.
An HDL level of 60 milligrams per deciliter or higher is desirable for both men and women, according to Mayo Clinic. Women are considered at risk if their HDL levels fall below 50 mg/dL, while men are at risk if their HDL levels are less than 40 mg/dL.
Cholesterol is just one of the factors used to determine if someone is at risk for heart disease. Other risk factors include high blood pressure, family history of heart disease, diabetes, obesity and lack of physical activity, according to the National Heart, Lung and Blood Institute.