Definition

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:

Alternative Names

Low-density lipoprotein test

How the test is performed

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.

How to prepare for the test

You will usually 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.

How the test will feel

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.

Why the test is performed

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

LDL carries cholesterol to various tissues throughout the body. Too much LDL, commonly called "bad cholesterol," is linked to cardiovasculardisease. The lower your LDL, the lower your risk for heart disease or stroke.

Normal Values

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.

What abnormal results mean

High levels of LDL may be associated with:

Increased risk of atherosclerotic heart disease
Familial hyperlipoproteinemia

Lower than normal levels of LDL may be caused by:

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

Additional conditions under which the test may be performed:

What the risks are

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)

References

Expert Panel on Detection, Evaluation, and Treatment of High Blood Cholesterol in Adults. Executive summary of the third report of the National Cholesterol Education Program (NCEP) expert panel on detection, evaluation, and treatment of high blood cholesterol in adults (Adult Treatment Panel III). JAMA. 2001;285:2486-2497. Updated 2004.

U.S. Preventive Services Task Force. Screening for lipid disorders in adults: U.S. Preventive Services Task Force recommendation statement. Rockville (MD): Agency for Healthcare Research and Quality (AHRQ); 2008 Jun.

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

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