The test for LDL cholesterol is used to predict your risk of developing heart disease. Of all the forms of cholesterol in the blood, the LDL cholesterol is considered the most important form in determining risk of heart disease. Since treatment decisions are often based on LDL values, this test may be used to monitor levels after the start of diet or exercise programs or to determine whether or not prescribing one of the lipid-lowering drugs would be useful.

LDL-C levels are ordered as part a lipid profile, along with total cholesterol, HDL, and triglycerides. This profile may be ordered as a screening profile in a healthy person as part of a routine physical exam. A lipid profile may be ordered on someone who has had a high screening cholesterol result to see if the total cholesterol is high because of too much LDL.

LDL-C levels may also be ordered at regular intervals to evaluate the success of lipid-lowering lifestyle changes such as diet and exercise or to determine the effectiveness of drug therapy such as statins.

Elevated levels of LDL cholesterol can indicate risk for heart disease, so your LDL-C result is evaluated with respect to the upper limits that are desired for you. According to the National Cholesterol Education Program, if you have no other risk factors, your LDL-C level can be evaluated as follows:

Less than 100 mg/dL (2.59 mmol/L) — Optimal

100-129 mg/dL (2.59-3.34 mmol/L) — Near optimal, above optimal

130-159 mg/dL (3.37-4.12 mmol/L) — Borderline high

160-189 mg/dL (4.15-4.90 mmol/L) — High

Greater than 189 mg/dL (4.90 mmol/L) — Very high

Major risk factors (see below) change the desired goals for LDL levels. Treatment (with diet or drugs such as statins) for high LDL-C aims to lower LDL cholesterol to a target value based on your overall risk of heart disease. Your target value is:

LDL less than 100 mg/dL (2.59 mmol/L) if you have heart disease or diabetes.*

LDL less than 130 mg/dL (3.37 mmol/L) if you have 2 or more risk factors (intermediate risk for heart disease).

LDL less than 160 mg/dL (4.14 mmol/L) if you have 0 or 1 risk factor (low risk for heart disease).

*Some organizations recommend that your LDL-C be less than 70 mg/dL (1.82 mmol/L) if you have heart disease or have had a heart attack.

Major risk factors include:

Cigarette smoking

Age (males 45 years or older or females 55 years or older)

Low HDL cholesterol (less than 40 mg/dL (1.04 mmol/L))

Hypertension (blood pressure of 140/90 or higher or taking high blood pressure medications)

Family history of premature heart disease (heart disease in a first degree male relative under age 55 or a first degree female relative under age 65)

Pre-existing coronary heart disease

Diabetes mellitus

[Note: High HDL cholesterol (60 mg/dL or above) is considered a "negative risk factor" and its presence allows the removal of one risk factor from the total.]

Low levels of LDL cholesterol are not generally a concern and are not monitored. They may be seen in patients with an inherited lipoprotein deficiency and in patients with hyperthyroidism, infection, inflammation, and cirrhosis.

LDL cholesterol should be measured when a person is not ill. LDL cholesterol is temporarily low during acute illness, immediately following a heart attack, or during stress (like from surgery or an accident). You should wait at least six weeks after any illness to have LDL cholesterol measured.

In women, LDL cholesterol usually rises during pregnancy. Women should wait at least six weeks after the baby is born to have LDL cholesterol measured.