Lipids are a group of fats and fat-like substances that are important constituents of cells and sources of energy. A lipid panel measures the level of specific lipids in the blood - Triglycerides, CHolesterol Total, HDL, LDL & VLDL Cholesterol. Two important lipids, cholesterol and triglycerides, are transported in the blood by lipoproteins (also called lipoprotein particles). Each type of lipoprotein contains a combination of cholesterol, triglyceride, protein, and phospholipid molecules. The particles measured with a lipid panel are classified by their density into high-density lipoproteins (HDL), low-density lipoproteins (LDL), and very low-density lipoproteins (VLDL).