Normal level of cholesterol in blood, illustration - stock illustration

Illustration of normal levels of cholesterol (yellow balls) in a blood vessel. Cholesterol is a lipid, a fat-like substance. High blood levels of LDL (low-density lipoprotein) cholesterol compared to HDL (high-density lipoprotein) cholesterol are thought to raise the risk of atherosclerosis, the build-up of fatty deposits on artery walls. This is a major cause of heart attack and stroke