What is being tested?
Cholesterol is a substance (a steroid) that is essential for life. It forms the membranes for cells in all organs and tissues in your body. It is used to make hormones that are essential for development, growth and reproduction. It forms bile acids that are needed to absorb nutrients from food. A small amount of your body’s cholesterol circulates in the blood in complex particles called lipoproteins. These lipoproteins include some particles that carry excess cholesterol away for disposal (see HDL, good cholesterol) and some particles that deposit cholesterol in tissues and organs (see LDL, bad cholesterol). The test for cholesterol measures all cholesterol (good and bad) that is carried in the blood by lipoproteins.

How is the sample collected for testing?
Most often a blood sample is collected from a vein in your arm. Sometimes cholesterol is measured using a drop of blood collected by puncturing the skin on a finger. A fingerstick sample is typically used when cholesterol is being measured on a portable testing device - for example at a health fair.

Is any test preparation needed to ensure the quality of the sample?
If a cholesterol test is to be performed alone, it is not necessary to fast. However, if it is to be performed as part of a lipid profile, as it often is, then fasting for at least 12 hours before the test will be required.