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Calculated LDL Cholesterol (Friedewald and Sampson/NIH)

Friedewald LDL-C = total cholesterol − HDL − triglycerides/5 (mg/dL); invalid when triglycerides >400 mg/dL. The Sampson/NIH equation 2 is more accurate at high triglycerides (up to 800 mg/dL) and low LDL. LDL ≥190 mg/dL indicates severe hypercholesterolemia.

  • Total cholesterol (mg/dL or mmol/L)
  • HDL cholesterol (mg/dL or mmol/L)
  • Triglycerides (mg/dL or mmol/L)
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Interpretation

ResultMeaning
< 70Very low / secondary-prevention target
70–99Optimal
100–129Near optimal
130–159Borderline high
160–189High
≥ 190Very high: severe hypercholesterolemia

Formula

Friedewald: LDL = TC − HDL − TG/5 (mg/dL; TG/2.2 in mmol/L) · Sampson/NIH eq. 2: LDL = TC/0.948 − HDL/0.971 − (TG/8.56 + TG × non-HDL/2140 − TG²/16100) − 9.44 (all mg/dL)

Clinical pearls

  • Friedewald underestimates LDL when LDL is low (< 70 mg/dL) or triglycerides are high (150–400); Sampson or Martin/Hopkins are more accurate there.
  • Non-fasting samples are acceptable for most purposes, but very high triglycerides need a direct LDL measurement.

Examples

ldl tc 200 hdl 50 tg 150calculate ldl cholesterol total 5.4 mmol/L hdl 1.2 triglycerides 2.1friedewald ldl chol 250 hdl 40 trigs 500

FAQ

When is the Friedewald equation not valid?

When triglycerides exceed 400 mg/dL (4.5 mmol/L), in type III dyslipoproteinemia, and it is less accurate at LDL below 70 mg/dL.

What is the Sampson (NIH) equation?

A 2020 equation using TC, HDL and TG that remains accurate up to triglycerides of 800 mg/dL and at low LDL levels.

Evidence

  1. Friedewald WT, Levy RI, Fredrickson DS. Estimation of the concentration of low-density lipoprotein cholesterol in plasma, without use of the preparative ultracentrifuge. Clin Chem 1972;18:499–502.
  2. Sampson M et al. A new equation for calculation of low-density lipoprotein cholesterol in patients with normolipidemia and/or hypertriglyceridemia. JAMA Cardiol 2020;5:540–8.

Cardiology · Reviewed 2026-10-14 · Methodology