How cholesterol is measured and tested?
Cholesterol is measured in units called millimoles per litre of blood, usually shortened to "mmol/litre" or "mmol/l". America uses the units milligrams per decilitre of blood: mg/dl instead. It is desirable to have a total cholesterol level under 5 mmol/l, and an LDL level under 3 mmol/l.
In order to estimate the risk of a person getting CHD, doctors look at the ratio between total cholesterol and high density lipoproteins ("good" cholesterol), called the TC:HDL ratio. A lower ratio is desirable, indicating that the level of HDL is high. Measuring cholesterol involves a simple blood test. A blood sample may be taken either by using a needle and a syringe, or by using a finger prick. This may be done at a GP's surgery, at a hospital appointment, or as part of a health assessment examination.
Home-testing kits for cholesterol are not recommended because they are not usually very reliable. Also, cholesterol is just one of the risk factors for heart disease. It should ideally be measured under medical supervision so that other important issues, such as blood pressure, age and whether or not you smoke, are taken into account.
Most blood cholesterol tests give the total cholesterol level. Knowing this level is an important first step in determining your risk for heart disease or stroke.
Usually a cholesterol test is done after a person has not eaten for several hours, often overnight. A simple blood draw is taken and tested. Blood cholesterol levels below 200 in middle-aged adults appear to be a good indication of a relatively low risk of coronary heart disease. Unless your level is high, you do not need to repeat this test very often. Adults over 20 years of age should have their blood cholesterol tested at least once every five years. It is also important to know what your HDL or "good" cholesterol level is. HDL cholesterol actually helps clear away 'bad' cholesterol from the blood vessels. 'Bad' cholesterol is called low-density lipoprotein.
Cholesterol is made by the body and is also present in food. Many parts of the body, such as the brain and the adrenal glands, depend on cholesterol for their proper function. However, cholesterol in excess can build up in places where it is harmful. Hereditary factors and too much saturated fat in the diet can cause harmful effects. It is the saturated fat in food that has the greatest effect on your blood cholesterol level.
One place where cholesterol causes trouble is in the walls of blood vessels. Too much blood cholesterol can make the blood vessel brittle or can block the flow of blood. Having unusually high levels of cholesterol in the blood increases the risk of heart attacks and strokes. The risk of having a heart attack or stroke is reduced by lowering blood cholesterol. This is why knowing your cholesterol levels is important.
Public or private testing is available. A private test can be done with your healthcare provider. Public screenings may be held in schools, churches, community centers or neighborhood clinics. They should be provided at reasonable cost and at sites that ensure quality control procedures and privacy. Screenings should include reliable verbal and printed information about cholesterol levels from knowledgeable staff.