how to ldl cholesterol calculation?

When you receive a report of your blood test for LDL cholesterol, you’ll see an amount measured in milligrams per deciliter of blood. While you should look at the normal values that the laboratory lists, your optimal LDL cholesterol level should be around 100 mg/dL or less.

Your LDL cholesterol is also a component of your total cholesterol — according to the Centers for Disease Control and Prevention (CDC), this number should be around 150 mg/dL.

Your LDL numbers may vary from lab to lab because each lab may use a different calculation. Some studies have detailed as many as 11 potential calculations that labs can use to calculate LDL cholesterol.

The Friedewald equation is a commonly used equation for calculating LDL cholesterol:

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

Some experts question the accuracy of using the triglycerides calculation, saying the calculation could cause a person’s LDL cholesterol to seem too low.

There’s a newer equation called the Martin or Martin-Hopkins equation. This calculation eliminates the triglycerides/5 value and replaces it with a variable number that depends on your triglyceride and non-high-density lipoprotein (HDL) levels.

A 2020 article in JAMA Cardiology on LDL calculations found the Martin equation to be more accurate than the Friedewald equation.

And in 2018, the American College of Cardiology and the American Heart Association recommended that laboratories use the Martin equation for calculating samples with low LDL cholesterol levels.

LabCorp, one of the largest laboratory organizations in the United States, uses the National Institutes of Health (NIH)‘s calculation for the LDL:

LDL Cholesterol = Total Cholesterol/0.948 − HDL Cholesterol/0.971 − (Triglycerides/8.56 + Triglycerides × Non-HDL Cholesterol/2,140 − Triglycerides2/16,100⁠) – 9.44

Their laboratory previously used the Friedewald equation.

[1] LDL can be calculated by FF (total cholesterol (TC) minus high-density lipoprotein (HDL)-cholesterol minus triglycerides (TGs)/5 in mg/dl) or measured directly in the laboratory. The FF is not valid for patients with TGs >400 and in patients for type 3 dyslipoproteinemia.