Alternative Names "Good" cholesterol, high-density lipoprotein
Definition High-density lipoprotein (HDL) is a type of cholesterol that is carried in the blood. An HDL test determines the level of HDL cholesterol in the blood. It is done to evaluate a person's risk of heart disease. HDL cholesterol is found only in the blood stream. It is not the same as dietary cholesterol found in food.
HDL is often referred to as the "good" cholesterol. This is because it transports excess blood cholesterol to the liver. There it is recycled or eliminated. As a result, desirable HDL levels are thought to help protect against coronary heart disease (CHD).
How is the test performed? The first step in measuring HDL is to take a blood sample. Blood is usually drawn from a vein in the forearm or the hand. The blood sample is sent to the laboratory to be analysed for HDL cholesterol. Most tests are done as cholesterol tests and then broken down to more specific cholesterol types. When having a cholesterol test performed always ask for a cholesterol profile. This will measure not only total cholesterol but also HDL and LDL ("bad" cholesterol). Total cholesterol does not tell the whole story. It is possible to have a low total cholesterol but a low HDL also.
What is involved in preparation for the test? A person having this test should receive instructions from a doctor on how to properly prepare. Fasting overnight before the blood sample is taken may be necessary. Some factors that can interfere with cholesterol testing results include epilepsy medication, diuretics, oral contraceptives, antibiotics, aspirin, hormones and drugs designed to lower cholesterol. Individuals having the test should let the laboratory know of any medications they may be taking.
What do the test results mean? A desirable level of HDL for adults is greater than 1.0 mmols/L (millimoles per litre). HDL levels above this range may indicate that the individual has a lower than normal risk of CHD. Abnormally low levels of HDL may indicate that a person is at increased risk of CHD.
Knowing one's cholesterol profile, including HDL is important. Lifestyle changes can help to correct undesirable results.
Author: David T. Moran, MD Reviewer: HealthAnswers Australia Medical Review Panel Editor: Dr David Taylor, Chief Medical Officer HealthAnswers Australia Last Updated: 1/10/2001 Contributors Potential conflict of interest information for reviewers available on request
