Cholesterol is a fat-like substance that is found in your blood. The two main types are low-density lipoprotein cholesterol (or LDL for short) and high-density lipoprotein cholesterol (or HDL). LDL cholesterol is sometimes called "bad" cholesterol. If you have high levels of it in your blood you have a higher risk of getting heart disease and having a heart attack. HDL cholesterol is often called "good" cholesterol. It removes LDL cholesterol from your blood. This keeps you from getting heart disease.

Your cholesterol level is affected by what you eat and how much you exercise. It's also affected by whether heart disease and heart attacks run in your family and whether you smoke. If you have a high level of LDL cholesterol, talk to your doctor about how you can lower it. To find out more, see our article on High cholesterol.

This information is for educational use only, and is not a substitute for prompt professional medical advice. Readers should always consult a physician or other professional for advice and treatment. ©BMJ Publishing Group Limited 2008. All rights reserved.