What cholesterol is

A substance the body needs

Cholesterol is a waxy, fat-like substance found in every cell. The body uses it to build cell membranes, make hormones such as estrogen and testosterone, produce vitamin D and make bile acids that help digest fat. The liver makes most of the cholesterol the body needs; the rest comes from food.

How it travels in blood

Cholesterol does not dissolve in blood, so it travels inside particles called lipoproteins. Low-density lipoprotein (LDL) carries cholesterol out to tissues; when LDL cholesterol stays high over time, it can build up inside artery walls and form the plaques behind heart attacks and strokes, which is why LDL is often called the 'bad' cholesterol.

High-density lipoprotein (HDL) carries cholesterol back toward the liver, and higher HDL is generally associated with lower risk. Triglycerides, another blood fat often measured in the same test, also matter for heart risk.

The blood test

A lipid panel is a simple blood test that reports total cholesterol, LDL, HDL and triglycerides. There are no symptoms of high cholesterol, so the test is the only way to know. What the numbers mean for any person depends on their overall risk profile - age, blood pressure, smoking, diabetes and family history - not on one number alone.

What can change it

Cholesterol levels respond to food patterns (less saturated and trans fat, more fiber), physical activity, weight and not smoking. Genetics also plays a large role; some people inherit very high cholesterol regardless of lifestyle. When risk is high enough, clinicians may add cholesterol-lowering medicines such as statins - an individual decision made with the treating clinician.