High cholesterol, or hypercholesterolemia, is a medical condition characterized by a higher than normal concentration of fats in the blood. These fats are produced naturally by the liver but can also be ingested in the foods we eat. Cholesterol is necessary for the production of hormones and the normal function of cell membranes. When cholesterol is too abundant in the blood, it can accumulate on the inside of blood vessels and reduce blood flow. People with high cholesterol are at an increased risk of stroke and heart disease.