Low-Density Lipoprotein (LDL)

  • Cholesterol is synthesized in the liver from dietary fats. It is transported in the blood by the low density lipoproteins (LDLs, or “bad” cholesterol) and high density lipoproteins (HDLs, or “good” cholesterol).
  • LDLs carry cholesterol from the liver to other parts of the body where it can cause atherosclerotic disease. High levels of LDL are associated with an increased risk for coronary artery disease (CAD).
  • To determine a target goal for LDL, risk factors must be determined. These include:

• Cigarette smoking
• Hypertension
• HDL <40 mg/dL
• Family history of premature CHD (male <age 55, female <age 65)
• Age (male ≥45, female ≥55)


  • If the HDL is ≥60 mg/dL, this is considered a “negative” risk factor, which removes one risk factor from the total count. The presence of diabetes mellitus is regarded as a CHD risk equivalent.

Target LDL levels, according to Adult Treatment Panel III (ATP III) guidelines, are:

  • With 0–1 cardiac risk factors: <160 mg/dL (<4.14 mmol/L SI units)
  • With ≥2 cardiac risk factors: <130 mg/dL (♥.36 mmol/L SI units)
  • With CAD or diabetes: <100 mg/dL (<2.6 mmol/L SI units)


It is now suggested by some research studies that individuals at very high risk of heart disease should have an LDL of <70 mg/dL. As a part of evaluating this risk, the low-density lipoprotein (LDL) level is measured as part of the lipid profile. In addition to actual measurement of the LDL, it can be calculated with the following formula:

LDL = Total Cholesterol − HDL − (Triglycerides/5)



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