Cholesterol is a waxy, fat-like substance that travels through the blood on proteins called lipoproteins. It comes from two sources:

  1. It's made by your body and used to do important things, like make hormones and digest fatty foods.

  2. It's found in many foods, like egg yolks, fatty meats, and regular cheese.

When your body has too much cholesterol, it can build up on the walls of your blood vessels. These deposits are called plaque. As your blood vessels build up plaque deposits over time, the inside of the vessels narrow and allows less blood to flow through to your heart and other organs.

When plaque buildup totally blocks a coronary artery carrying blood to the heart, it causes a heart attack. Another cause of heart attack is when a plaque deposit bursts and releases a clot in a coronary artery. Angina is caused by plaque partially blocking a coronary artery, reducing blood flow to the heart and causing chest pain.

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A cholesterol screening measures your level of high-density lipoprotein (HDL) cholesterol, low-density lipoprotein (LDL) cholesterol and triglycerides. A small sample of blood will be drawn from your arm. If your doctor orders other tests to be run at the same time as your cholesterol test, all the samples are usually taken at the same time. Your blood sample is then analyzed in a laboratory.

Your doctor will tell you if you should fast (avoid consuming food, beverages and medications, usually for nine to 12 hours) before your blood test. If you aren't fasting when the blood sample is drawn, only the values for total cholesterol and HDL cholesterol will be usable. That's because the amount of LDL (bad) cholesterol level and triglycerides can be affected by what you've recently consumed.

Your test report will show your cholesterol level in milligrams per deciliter of blood (mg/dL). Your doctor will interpret your cholesterol numbers based on other risk factors such as age, family history, smoking and high blood pressure.