If too much cholesterol is carried around in the blood stream, it may be deposited in gradually increasing amounts inside the arteries. Slowly, the affected artery narrows, until the flow of blood is sufficiently obstructed to cause the area supplied by that artery to suffer. If that area is the heart, a heart attack will result; if it is the brain, a stroke will occur. This deposition of fat is known as arteriosclerosis, or hardening of the arteries.
It has been proven that if cholesterol levels that are within normal limits, the risk of heart attack is greatly reduced. It is therefore important for anyone who feels they may be at risk, and everyone at 40 years of age, to have a blood test to determine their cholesterol level. For this test to be accurate, it is necessary to fast for 12 hours (usually overnight), and avoid alcohol for 72 hours before the blood sample is taken.
If the total cholesterol level is below 4.5 mmol/L, there is no need for concern. If it is above 5.0 mmol/L, the doctor will probably order tests to find out what types of cholesterol are present. Lower levels of cholesterol are of concern in patients who have diabetes, a history of heart attack or stroke, smokers and with some other diseases. Levels should also be lower in young people than old, and males than females.