What does the LDL Cholesterol (directly measured) test measure?

Why is LDL Cholesterol (directly measured) measured?

Direct LDL-C is the principal target of lipid-lowering therapy, measured analytically rather than derived. Its value lies in the settings where calculated LDL-C fails — notably triglycerides above roughly 400 mg/dL, very low LDL-C, and non-fasting samples — where the Friedewald estimate is invalid or inaccurate. Direct assays are not fully standardised across manufacturers and can themselves be affected by marked hypertriglyceridaemia, so non-HDL-C and ApoB remain valuable comparators.

Reference ranges

Standard reference

Optimal: <100 mg/dL (<2.6 mmol/L); progressively lower targets apply at higher cardiovascular risk # REVIEWER FLAG: LDL-C targets are risk-stratified and guideline-dependent (ACC/AHA, ESC/EAS) rather than a fixed reference range — reviewer to confirm framing and units.

Functional medicine optimal

<100 mg/dL in low-risk patients; <70 mg/dL or <55 mg/dL in high and very-high-risk patients # REVIEWER FLAG: Risk-stratified LDL-C targets are guideline-dependent — reviewer to confirm.

Units

mg/dL, mmol/L

Reference ranges vary by laboratory and assay platform. Interpret in context of the issuing laboratory's stated range.