High density lipoprotein, abbreviated HDL, is considered "good" cholesterol because it carries dangerous low density lipoprotein, abbreviated LDL, to the liver to be broken down and eliminated from the body. What makes LDL "bad cholesterol" is that it causes a thick and rigid deposit called plaque to build up in the arteries, potentially resulting in heart disease or stroke.
A person's cholesterol level can be determined by a simple blood test known as a lipid profile. This test actually measures not only HDL and LDL but also a third substance called triglycerides, which are a type of fat. Triglycerides store energy from food that is left over after the body's needs have been met.
High levels of triglycerides can be caused by being overweight, too little physical activity, cigarette smoking and excessive consumption of alcohol or carbohydrates. Intake of carbohydrates is considered excessive when it comprises more than 60 percent of the diet. High triglyceride levels also may be caused by underlying diseases or genetic disorders. Elevated triglyceride levels are associated with atherosclerosis, a hardening of the arteries caused by plaque buildup.
Cholesterol cannot dissolve in the blood but instead must be removed by carriers known as lipoproteins. The lipoproteins are so called because they are molecules made of both fat (lipid) and proteins. Total cholesterol count consists of LDL, HDL and one-fifth of the triglyceride level.