(Note: The information in this article is for adults who want to prevent heart disease. It is not intended for people who have been diagnosed with diabetes or heart disease—heart attack, angina, coronary artery disease—or who have had heart surgery, a balloon or angioplasty procedure, or an angiogram that showed a blockage in a coronary artery.) 

High cholesterol is one of the leading risk factors for the development of coronary heart disease (CHD). The higher your cholesterol level, the greater your CHD risk. The good news: High cholesterol levels can be lowered by diet and exercise or medicine. The National Heart, Lung, and Blood Institute (NHLBI) recommends that everyone 20 years and older have a blood cholesterol measured at least every five years.

Cholesterol is a waxy substance that occurs naturally in all parts of the body. It helps produce hormones, vitamin D, and the bile acids that help to digest fat, as well as having other functions. It takes only a small amount of cholesterol in the blood for these functions. The body gets cholesterol in two ways: by making it in the liver or by obtaining it from foods. Too much cholesterol in blood can lead to atherosclerosis. This is a condition in which fat and cholesterol are deposited in the walls of the arteries, including the coronary arteries that supply oxygen and nutrition to the heart. In time, narrowing of the coronary arteries by atherosclerosis can cause a heart attack or angina.   

Cholesterol is measured by a simple blood test. The best test, according to the NHLBI, is a lipoprotein profile, which requires that you not eat nine to 12 hours before the test. If it is not possible to have a lipoprotein profile, then having a nonfasting test that measures total cholesterol level and a high-density lipoprotein (HDL) cholesterol level can give a general idea about your cholesterol levels.

Higher numbers, higher risk

Total cholesterol level is the sum of all the cholesterol in the blood. The higher the total cholesterol, the greater the risk for heart disease. Optimal total cholesterol is less than 200 mg/dL.

HDL is known as the "good cholesterol" because it carries cholesterol back to the liver, where it is removed from the body. HDL helps keep cholesterol from building up on the walls of arteries. The higher the HDL level, the better. An optimal level is 60 mg/dL or higher.

If your cholesterol level is 200 mg/dL or more, or if you HDL is too low (40 mg/dL or lower), you will need to have a fasting lipoprotein profile. Doctors now suggest that an HDL of 60 mg/dL, or higher, is optimal.

A fasting lipoprotein level will show the level of LDL ("bad") cholesterol and triglycerides, a form of fat carried in the blood.

LDL is the main carrier of cholesterol in the blood and is the main source of damaging buildup of cholesterol in the arteries. Lowering the LDL cholesterol level is the main goal of cholesterol-lowering treatment. An optimal LDL cholesterol level is less than 100 mg/dL.

Triglycerides are another form of fat found in the body, as well as in food. Usually, only a small amount of triglycerides is found in the blood. A high triglycerides level often accompanies other risk factors, such as diabetes, and may be a sign of a cholesterol problem, such as low HDL, that contributes to heart disease.

On the border

A borderline high or high level of LDL cholesterol (above 130 mg/dL) or a low level of HDL cholesterol (less than 40 mg/dL) can increase your risk for heart disease. A borderline high (150 to 199 mg/dL) or high (200 mg/dL or greater) level of triglycerides also can raise your risk for heart disease.

In addition to high cholesterol, you may have other important risk factors for heart disease. These should be included in an assessment of your risk for heart attack. Some of these can be reduced or eliminated; some cannot be changed. Risk factors you can change include being obese, having a sedentary lifestyle, and smoking. Risk factors you cannot change include being a male older than 45, or a female older than 55, or having a father, brother, mother, or sister who had early heart disease.