How to estimate LDL cholesterol
Use a standard lipid panel with consistent units.
Enter the lipid panel
Use total cholesterol, HDL and triglycerides from the same blood draw.
Match the units
Choose mg/dL or mmol/L; the formula adjusts the triglyceride divisor.
Check the triglyceride limit
If triglycerides are high, the result explains why a direct LDL test is needed.
What does this tool do?
The Friedewald equation estimates LDL cholesterol without a direct assay by subtracting HDL and an assumed VLDL fraction. It is convenient but becomes unreliable when triglycerides are high, so the result is shown with that limit.
The Formula
LDL = total cholesterol − HDL − triglycerides ÷ 5 (mg/dL); for mmol/L use triglycerides ÷ 2.2Frequently Asked Questions
Why can triglycerides make the estimate invalid?
Friedewald assumes VLDL cholesterol is triglyceride divided by five. Above about 400 mg/dL that assumption is unreliable, so a direct LDL measurement is preferred.
Is this the same as a direct LDL test?
No. A direct assay measures LDL without assuming a VLDL fraction. Use the laboratory result your clinician orders for treatment decisions.