A high-density lipoprotein (HDL) test measures the level of good cholesterol in your blood. Cholesterol is a waxy substance that’s found in all of the cells in your body. It has several different functions, including helping to build your body’s cells. Cholesterol is carried through the bloodstream attached to proteins called lipoproteins. Two types of cholesterol in your body are HDL, which is the good cholesterol, and low-density lipoprotein (LDL), or bad cholesterol. HDL is known as the good cholesterol because it carries LDL, triglycerides, and harmful fats and returns them to your liver for processing. When HDL reaches your liver, the liver breaks down the LDL, turns it into bile, and removes it from your body.
