Blood-tests Explained


Disclaimer:

This website is intended to assist with patient education and should not be used as a diagnostic, treatment or prescription service, forum or platform. Always consult your own healthcare practitioner for a more personalised and detailed opinion

Cholesterol


At a Glance

Why Get Tested?

To screen for risk of developing heart disease; to monitor effectiveness of lipid-lowering therapy

When to Get Tested?

Screening: as part of a regular health exam with a lipid profile when no risk factors for heart disease are present; adults should be tested once every four to six years; children, teens, and young adults should be tested once between the ages of 9 and 11 and then again between the ages of 17 and 21.

Monitoring: may be done more frequently and at regular intervals when risk factors for heart disease are present, when prior results showed high risk levels, and/or when undergoing treatment for unhealthy lipid levels

Sample Required?

A blood sample drawn from a vein in your arm or from a fingerstick

Test Preparation Needed?

If you are having this test performed as part of the lipid profile, typically you will need to fast for 9-12 hours before the sample is collected; only water is permitted. Your healthcare practitioner may decide that you may be tested without fasting. Follow any instructions you are given and tell the person drawing your blood whether or not you have fasted. For youths without risk factors, testing may be done without fasting.

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 the 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. The test for cholesterol measures total cholesterol that is carried in the blood by lipoproteins.

A small amount of cholesterol circulates in the blood in complex particles called lipoproteins. Each particle contains a combination of protein, cholesterol, triglyceride, and phospholipid molecules and the particles are classified by their density into high-density lipoproteins (HDL), low-density lipoproteins (LDL), and very low-density lipoproteins (VLDL). HDL-C particles, sometimes called "good" cholesterol, carry excess cholesterol away for disposal and LDL-C particles, or "bad" cholesterol, deposit cholesterol in tissues and organs.

Monitoring and maintaining healthy levels of cholesterol is important for staying healthy. The body produces the cholesterol needed to work properly, but the source for some cholesterol is diet. If an individual has an inherited predisposition for high cholesterol levels or eats too much of the foods that are high in saturated fats and trans unsaturated fats (trans fats), then the level of cholesterol in that person's blood may increase and have a negative impact on the person's health. The extra cholesterol in the 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 increased risk of numerous health problems, including heart disease and stroke.

How is the sample collected for testing?

Most often, a blood sample is collected from a vein in the 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.

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

Cholesterol tests typically require fasting for 9-12 hours before the test; only water is permitted. Your healthcare practitioner may decide that you may be tested without fasting. Follow any instructions you are given and tell the person drawing your blood whether or not you have fasted. For youths without risk factors, testing may be done without fasting.

The Test