LDL cholesterol

Low-density lipoprotein cholesterol, often called the harmful cholesterol, is the form that collects in artery walls; high levels raise the risk of heart attacks and strokes.

Cholesterol travels through the blood wrapped in particles called lipoproteins. Low-density lipoprotein, or LDL, is one of the main carriers, and the cholesterol it delivers is the kind that can collect on the inside of artery walls. Over years this build-up narrows and stiffens the arteries, a process called atherosclerosis, which is why LDL is often described as the harmful or bad cholesterol.

Doctors measure LDL cholesterol from a blood sample, usually reported in milligrams per decilitre (mg/dL) in the United States or millimoles per litre (mmol/L) elsewhere. For people at risk of cardiovascular disease, lower is generally better. Lowering LDL, whether through diet, exercise or medicines such as statins, reduces the chance of heart attacks and strokes, and it is the main target of most cholesterol treatments. Because a high LDL level itself causes no symptoms, many people only learn theirs through a routine blood test.

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