LDL Cholesterol (Friedewald Formula)
Estimates LDL cholesterol from total cholesterol, HDL cholesterol, and triglycerides using the standard Friedewald equation.
Warnings:
- Formula is NOT valid when triglycerides >400 mg/dL (some sources say >500 mg/dL)
- Accuracy decreases with TG 200-400 mg/dL; use caution in this range
- Formula assumes VLDL cholesterol = TG/5, which is an approximation
- In type III hyperlipoproteinemia (dysbetalipoproteinemia), formula is unreliable
- For mmol/L: LDL (mmol/L) = Total - HDL - (TG/2.2)
- Martin-Hopkins or Sampson modified formulas may be more accurate in hypertriglyceridemia
Note: Alternative modified formula for improved accuracy with TG 200-400 mg/dL: LDL = Non-HDL x 0.9 - (TG x 0.1). Non-HDL = Total - HDL. For SI units: LDL (mmol/L) = Total (mmol/L) - HDL (mmol/L) - [TG (mmol/L) / 2.2].
Total serum cholesterol concentration
HDL (good) cholesterol concentration
Fasting triglycerides concentration. Formula unreliable if TG >400 mg/dL
References
- A modified formula for calculating low-density lipoprotein cholesterol values - Journal of Clinical Laboratory Analysis / PMC (2010)
- Estimation of the concentration of low-density lipoprotein cholesterol in plasma, without use of the preparative ultracentrifuge - Clinical Chemistry (Friedewald WT et al.) (1972)