What is cholesterol?    Cholesterol is a soft, fat-like, waxy substance found in the bloodstream and in all your body's cells. It's normal to have cholesterol. Cholesterol is an important part of a healthy body because it's used for producing cell membranes and some hormones, and serves other needed bodily functions. But too much cholesterol in the blood is a major risk for coronary heart disease (which leads to heart attack) and for stroke. Hypercholesterolemia is the medical term for high levels of blood cholesterol. The sources of cholesterol   Cholesterol comes from two sources: your body and food. Your liver and other cells in your body make about 75 percent of blood cholesterol. The other 25 percent comes from the foods you eat. LDL cholesterol is the “bad” cholesterol. When too much of it circulates in the blood, it can clog arteries, increasing the risk of heart attack and stroke. LDL cholesterol is produced naturally by the body, but many people inherit genes from their mother, father or even grandparents that cause them to make too much. Eating saturated fat, trans fats and dietary cholesterol also increases how much you have. If high blood cholesterol runs in your family, lifestyle modifications may not be enough to help lower your LDL blood cholesterol. Everyone is different, so work with your doctor to find a treatment plan that's best for you. Cholesterol can’t dissolve in the blood. It has to be transported to and from the cells by carriers called lipoproteins. Low-density lipoprotein, or LDL, is known as “bad” cholesterol. High-density lipoprotein, or HDL, is known as “good” cholesterol. These two types of lipids, along with triglycerides and Lp(a) cholesterol, make up your total cholesterol count, which can be determined through a blood test.  LDL and HDL cholesterol: what's bad and what's good? LDL (Bad) Cholesterol When too much LDL (bad) cholesterol circulates in the blood, it can slowly build up in the inner walls of the arteries that feed the heart and brain.  Together with other substances, it can form plaque, a thick, hard deposit that can narrow the arteries and make them less flexible.  This condition is known as atherosclerosis. If a clot forms and blocks a narrowed artery, heart attack or stroke can result. HDL (good) Cholesterol About one-fourth to one-third of blood cholesterol is carried by high-density lipoprotein (HDL). HDL cholesterol is known as “good” cholesterol, because high levels of HDL seem to protect against heart attack. Low levels of HDL (less than 40 mg/dL) also increase the risk of heart disease. Medical experts think that HDL tends to carry cholesterol away from the arteries and back to the liver, where it's passed from the body. Some experts believe that that HDL removes excess cholesterol from arterial plaque, thus slowing its buildup. Triglycerides Triglyceride is a form of fat made in the body. Elevated triglycerides can be due to overweight/obesity, physical inactivity, cigarette smoking, excess alcohol consumption and a diet very high in carbohydrates (60 percent of total calories or more). People with high triglycerides often have a high total cholesterol level, including a high LDL (bad) level and a low HDL (good) level. Many people with heart disease and/or diabetes also have high triglyceride levels. Lp(a) Cholesterol Lp(a) is a genetic variation of LDL (bad) cholesterol. A high level of Lp(a) is a significant risk factor for the premature development of fatty deposits in arteries. Lp(a) isn’t fully understood, but it may interact with substances found in artery walls and contribute to the buildup of fatty deposits. What can cholesterol do? High cholesterol is one of the major controllable risk factors for coronary heart disease, heart attack and stroke.  As your blood cholesterol rises, so does your risk of coronary heart disease. If you have other risk factors (such as high blood pressure or diabetes) as well as high cholesterol, this risk increases even more. The more risk factors you have, the greater your chance of developing coronary heart disease. Also, the greater the level of each risk factor, the more that factor affects your overall risk. When too much LDL (bad) cholesterol circulates in the blood, it can slowly build up in the inner walls of the arteries that feed the heart and brain. Together with other substances, it can form plaque, a thick, hard deposit that can narrow the arteries and make them less flexible.  This condition is known as atherosclerosis. If a clot forms and blocks a narrowed artery, a heart attack or stroke can result.