If eating right and exercising more don't help to lower your cholesterol levels, your doctor may suggest statins.

By now, you're probably tired of doctors, drug ads, health experts—and maybe even smart-aleck magazine articles like this one—nagging you about lowering your cholesterol. Perhaps you're even among the 20 million or so Americans who already take a cholesterol-lowering drug. But have you been getting the best advice? And, with some cholesterol drugs costing $100 or more per month, how do you know which one is right for you?

To answer those questions, let's start with some of the basics about this fatty substance—cholesterol—that can build up on artery walls and lead to heart disease, heart attacks, and strokes.

Doctors have known for decades that people with too much cholesterol in their blood run a higher risk of heart disease. But research since the late 1980s has painted a more complex picture. For starters, there are many types of cholesterol, and they are identified by certain molecules, called lipoproteins, that carry cholesterol around in the blood. Two types are typically measured. One is called low-density lipoprotein (LDL) cholesterol. It's often referred to as the "bad" kind because it can clump together on the walls of arteries and clog them, just like a congested drain pipe. So, an elevated LDL level is not good and most cholesterol drugs were developed to lower it.

The other type is called high-density lipoprotein (HDL) cholesterol. It's known as the good kind because—among other things—it plays a role in clearing cholesterol out of the bloodstream. Doctors like to see your HDL above a certain level (see What your readings mean); if it falls below that, they worry. And so some drugs are specifically designed to raise HDL as well as lower LDL.

The problem is that a lot of people—half or more—who have a first heart attack don't have either high LDL or low HDL. That means that cholesterol and lipoprotein levels are not the only culprits raising your risk of heart problems. Even so, a high LDL and/or low HDL do significantly raise your risk, and that's why doctors focus on keeping your cholesterol and lipoproteins at healthy levels.

The first stop in that effort is a blood test. About 70 percent of American adults have had their lipoprotein levels checked, but that leaves 30 percent who haven't. The National Institutes of Health advises all people 20 years and older to have their lipoproteins checked at least once every five years. If you have risk factors for heart disease (such as smoking, diabetes, or high blood pressure), or are over 60, we recommend that you get tested more often. The same blood test will measure triglycerides, another type of fat linked to heart risk, and also C-reactive protein, an indicator of inflammation in your arteries.