High cholesterol does not cause any symptoms, so people can have excessively high levels without knowing it. High blood cholesterol (de?ned as a level of 240 mg/dL or higher) is among the most impor- tant risk factors for developing heart disease. In countries such as Japan, which until recently had cholesterol levels averaging only 150 mg/dL, heart disease has been very rare.
All adults over the age of 20 should have their cholesterol measured at least once every 5 years with a blood test called a full lipoprotein pro- ?le. Children in families with premature heart disease may be screened starting at age 2. A full lipid pro?le measures not only the total choles- terol but also HDL and triglycerides. Your doctor looks at all of these numbers, as well as your other risk factors for heart
disease, and then can use a risk assessment tool to estimate your chances of having a heart attack in the next 10 years. Knowing your risk enables you to take steps to improve your cardiovascular health and lower your chances of heart disease and stroke.
To have your cholesterol tested, you need to go to your doctor or a medical laboratory. The results from tests performed at shopping centers or health fairs are not as reliable as having your blood sample analyzed at an approved labora- tory. Reliable testing requires a fasting blood sample. A nonfasting sample does not allow an accurate determination of LDL, which is the most important indicator of your heart attack risk. You should do the following to prepare for the blood test:
• For 10 to 12 hours before testing (often overnight), you may not eat or drink any- thing except water.
• You can eat as you usually do until 10 to 12 hours before the test.
• You might be asked not to drink any alcohol for several days before testing, because alco- hol can affect triglyceride levels.
Home Cholesterol Testing
You may see home cholesterol testing kits for sale in some drugstores. Some measure only total cholesterol, or only total cholesterol and HDL. At least one is designed to test HDL, LDL, triglycerides, and total cholesterol. There is no harm in trying one of these devices, or having your choles- terol checked at a health fair, but these tests do not take the place of a laboratory-analyzed lipoprotein pro- file (which requires you to fast before the test).
If you try one of these methods and the results indicate that your total cholesterol is 200 mg/dL or more, fol- low up with a full profile done by trained professionals.
Most laboratories do not measure your LDL directly but calculate it by subtracting your HDL from your total cholesterol level, then subtracting one-fifth of your triglyceride level. This figure is your LDL. In cases of markedly elevated triglycerides, direct testing of LDL is needed.
• If you are sick on the appointed day, the test should be rescheduled.
• Before the day of the test, check with your doctor as to which of your regular medications, if any, you should take at home in the morning.