An HDL cholesterol test measures the amount of cholesterol found inside high-density lipoproteins (HDL) in a sample of your blood. Cholesterol is a waxy substance that helps the cells in your body function properly. However, buildup of certain types of cholesterol in your arteries can heighten the risk of heart disease, stroke, heart attacks, and other health problems. HDL cholesterol (HDL-C) is often known as good cholesterol because it is associated with better cardiovascular health. In contrast, low-density lipoprotein (LDL) cholesterol is called bad cholesterol because it is associated with cardiovascular disease. HDL cholesterol is almost always measured along with total cholesterol, and these two measurements are core parts of the lipid panel test.