LDL stands for low-density lipoprotein. It's also sometimes called "bad" cholesterol. Lipoproteins are made of fat and protein. They carry cholesterol, triglycerides, and other fats, called lipids, in the blood to various parts of the body.

This article discusses the blood test to measure the level of LDL cholesterol in your blood. Too much LDL in the blood can clog arteries.

See also:

• High-density lipoprotein (HDL) test
• Total cholesterol test
• High blood cholesterol and triglycerides

Low-density lipoprotein test

Blood is typically drawn from a vein, usually from the inside of the elbow or the back of the hand. The site is cleaned with germ-killing medicine (antiseptic). The health care provider wraps an elastic band around the upper arm to apply pressure to the area and make the vein swell with blood.

Next, the health care provider gently inserts a needle into the vein. The blood collects into an airtight vial or tube attached to the needle. The elastic band is removed from your arm.

Once the blood has been collected, the needle is removed, and the puncture site is covered to stop any bleeding.

In infants or young children, a sharp tool called a lancet may be used to puncture the skin and make it bleed. The blood collects into a small glass tube called a pipette, or onto a slide or test strip. A bandage may be placed over the area if there is any bleeding.

You may be told not to eat or drink anything for 9 - 12 hours before the test.

The health care provider may tell you to stop taking certain drugs before the procedure.

When the needle is inserted to draw blood, you may feel moderate pain, or only a prick or stinging sensation. Afterward, there may be some throbbing.

This test is usually done to determine your risk for heart disease. The LDL test is usually done as part of a lipid analysis, which also checks total cholesterol, HDL, and triglyceridelevels.

LDL carries cholesterol to various tissues throughout the body. Too much LDL, commonly called "bad cholesterol," can lead to cardiovascular disease.

According to the National Heart, Lung, and Blood Institute, the lower your LDL, the lower your risk for heart disease or stroke.

A healthy LDL level is one that falls in the optimal or near-optimal range.

• Optimal: Less than 100 mg/dL (less than 70 mg/dL for persons with a history of heart disease or those at very high risk for atherosclerotic disease)
• Near Optimal: 100 - 129 mg/dL
• Borderline High: 130 - 159 mg/dL
• High: 160 - 189 mg/dL
• Very High: 190 mg/dL and higher

Note: Normal value ranges may vary slightly among different laboratories. Talk to your doctor about the meaning of your specific test results.

High levels of LDL may be associated with:

• Increased risk of atherosclerotic heart disease
• Familial hyperlipoproteinemia

• Malabsorption (inadequate absorption of nutrients from the intestinal tract)
• Malnutrition

• Familial combined hyperlipidemia
• Familial dysbetalipoproteinemia
• Familial hypertriglyceridemia

Veins and arteries vary in size from one patient to another and from one side of the body to the other. Obtaining a blood sample from some people may be more difficult than from others.

Other risks associated with having blood drawn are slight but may include:

• Excessive bleeding
• Fainting or feeling light-headed
• Hematoma (blood accumulating under the skin)
• Infection (a slight risk any time the skin is broken)

Implications of recent clinical trials for the National Cholesterol Education Program Adult Treatment Panel III guidelines. Circulation. 2004 Jul 13; 110(2):227-39.

Semenkovich CF. Disorders of lipid metabolism. In: Goldman L, Ausiello D, eds. Cecil Medicine. 23rd ed. Philadelphia, Pa: Saunders Elsevier; 2007:chap 217.