Empeiria

LDL cholesterol (calculated)

Also known as LDL, bad cholesterol

lipid class · no single molecular formula

LOINC 13457-7 code verified serum mg/dL

What this substance is

Cholesterol carried within a lipoprotein particle class, not a distinct molecule. And usually not measured at all: most labs calculate it.
How it is calculated

Friedewald: LDL = total cholesterol - HDL - (triglycerides / 5) mg/dL

Derived from cholesterol_total, hdl_cholesterol, triglycerides.

What is counted: cholesterol carried in LDL particles

Each molecule is drawn from ChEBI's curated 2D drawing, accepted only after its InChIKey, formula and charge matched the ChEBI release. Atom diagrams are checked against the NIST Atomic Spectra Database.

3D model · cholesterol

What is counted: cholesterol carried in LDL particles. Generated by RDKit from ChEBI's verified structure, and accepted only because its own 3D geometry reproduces ChEBI's InChIKey. A flexible molecule takes many shapes; this is one low-energy one. Drag to rotate, scroll to zoom.

Reference ranges

Checking your own result against this range needs the running application; this is a static copy. Nothing you type anywhere in Empeiria is ever sent to a server.

all
100
normal range · mg/dL
Applies toNormalOptimalCritical
all ≤ 100 mg/dL — —

guideline limit ATP III Guidelines At-A-Glance Quick Desk Reference, National Cholesterol Education Program (NHLBI) cited · not yet checked by a person

How it is measured

In practice

LDL is checked from a blood sample taken from a vein in your arm, as part of a cholesterol test. You may need to skip food and drink for 9 to 12 hours first. Most often LDL is not measured on its own. It is worked out from your total cholesterol, HDL and triglycerides, but it can also be measured directly. Home kits that use a drop of blood from a finger prick also exist.

LDL-C is usually calculated from the standard lipid panel (total cholesterol, triglycerides, HDL-C) on the same venous sample, classically by the Friedewald equation, which is not used when TG > 400 mg/dL and underestimates LDL-C at low levels. The Martin-Hopkins (2013) and Sampson-NIH / Modified Sampson-NIH equations improve accuracy across a wider TG range. Some laboratories use automated direct (homogeneous) LDL-C assays, which can deviate from the beta-quantification (ultracentrifugation) reference method in dyslipidaemic samples. Fasting for 9-12 hours may be requested.

Before the test

  • Fast (no food or drink) for 9 to 12 hours before the test if your provider asks.

Where: laboratory

Sources: Cholesterol Levels -- MedlinePlus Medical Tests, U.S. National Library of Medicine; Wolska A et al. New Methods for Calculating LDL-Cholesterol and Related Biomarkers of Atherosclerotic Cardiovascular Disease Risk. Curr Atheroscler Rep 2026 (NHLBI/NIH authors; PMC open access) cited · not yet checked by a person

In the lab

calculation

Friedewald equation

Usually not measured. It is worked out by subtracting the other fats from the total, which means an error in any of them lands here too.

LDL = TC - HDL - TG/5 (mg/dL)

Why labs disagree: The equation is not valid when triglycerides are above 400 mg/dL, and it underestimates LDL when LDL is low (below 70 mg/dL) or triglycerides are high, which is why newer equations such as Martin-Hopkins or NIH equation 2 are preferred in those situations.

Source: NHANES 2017-2018 Data Documentation: Cholesterol - LDL & Triglycerides (TRIGLY_J), CDC/NCHS cited · not yet checked by a person

What it reports on

Associated symptoms

Conditions this marker features in

When high
  • high Unhealthy cholesterol levels · defining
    Classification, not a single diagnostic test: in the NCEP ATP III scheme an LDL of 160–189 mg/dL is 'high' and 190 or more 'very high'. LDL is the main target of treatment.
  • high Mildly underactive thyroid · supportive
    Study results are mixed. One large study found higher LDL cholesterol only in women.

Ordered as part of

lipid · metabolic_risk