Hypercholesterolemia is a condition in which the level of cholesterol in your blood is high. When you have too much cholesterol, deposits of fat in the blood called plaque form inside blood vessel walls. The blood vessel walls thicken and become narrower (a condition called atherosclerosis). This change reduces blood flow through the blood vessels, increasing your risk of heart disease and possibly leading to a heart attack or stroke.

Cholesterol is a fatty substance, also called a lipid. Your body needs small amounts of this substance to make and maintain nerve cells and to produce hormones. Most of the cholesterol in your blood is made by your liver from the fats, carbohydrates, and proteins you eat. You also get cholesterol by eating animal products such as meat, eggs, and dairy products.

The two most important components of cholesterol measurements are LDL and HDL. LDL and HDL carry cholesterol through your blood. LDLs carry a lot of cholesterol, leave behind fatty deposits on your artery walls, and contribute to heart disease. HDLs do the opposite: They clean the artery walls and remove extra cholesterol from the body, thus lowering the risk of heart disease. LDL is called "bad" cholesterol. (You can think of "L" for "lousy" cholesterol.) HDL is called "good" cholesterol (think of "H" for "healthy" cholesterol). It is good to have low levels of LDL and high levels of HDL.

The main cause of high cholesterol is eating foods that are high in saturated fat or cholesterol. Other possible causes are:

• an inherited problem with the way your body processes cholesterol
• a disease that raises the cholesterol level (for example, diabetes, kidney disease, liver disease, or hypothyroidism).
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