Cholesterol

Also known as: Blood cholesterol

Formal name: Total cholesterol

Related tests: HDL-C, LDL-C, Triglycerides, Lipid profile, Cardiac risk assessment

The Test Sample

What is being tested?

Cholesterol is a substance (a steroid) that is essential for life. It forms the membranes for cells in all organs and tissues in your body. It is used to make hormones that are essential for development, growth, and reproduction. It forms bile acids that are needed to absorb nutrients from food. A small amount of your body’s cholesterol circulates in the blood in complex particles called lipoproteins. These lipoproteins include some particles that carry excess cholesterol away for disposal (see HDL-C, good cholesterol) and some particles that deposit cholesterol in tissues and organs (see LDL-C, bad cholesterol). The test for cholesterol measures total cholesterol (good and bad) that is carried in the blood by lipoproteins.

Your body produces the cholesterol needed to work properly, but the source for some cholesterol is your diet. If you have an inherited predisposition for high cholesterol levels or if you eat too much of the foods that are high in cholesterol, saturated fats, and trans unsaturated fats (trans fats), then levels of cholesterol in your blood may increase and have a negative impact on your health. The extra cholesterol in your blood may be deposited in plaques on the walls of blood vessels. Plaques can narrow or eventually block the opening of blood vessels, leading to hardening of the arteries (atherosclerosis) and increasing your risk of numerous health problems, including heart disease and stroke.

Monitoring and maintaining healthy levels of cholesterol is important in staying healthy.

How is the sample collected for testing?

Most often, a blood sample is collected from a vein in your arm. Sometimes cholesterol is measured using a drop of blood collected by puncturing the skin on a finger. A fingerstick sample is typically used when cholesterol is being measured on a portable testing device - for example, at a health fair.

NOTE: If undergoing medical tests makes you or someone you care for anxious, embarrassed, or even difficult to manage, you might consider reading one or more of the following articles: Coping with Test Pain, Discomfort, and Anxiety, Tips on Blood Testing, Tips to Help Children through Their Medical Tests, and Tips to Help the Elderly through Their Medical Tests.

Another article, Follow That Sample, provides a glimpse at the collection and processing of a blood sample and throat culture.

Is any test preparation needed to ensure the quality of the sample?

If a cholesterol test is to be performed alone, it is not necessary to fast. However, if it is to be performed as part of a lipid profile, as it often is, then fasting for 9-12 hours before the test will be required; only water is permitted.