LDL Cholesterol is often not measured directly, but calculated using an equation which uses the other components of the lipid profile: Total Cholesterol, HDL Cholesterol and Triglycerides. If the LDL is not calculated directly, we call this “Friedewald derived LDL-cholesterol“.
If calculated using all concentrations in mg/dL then the equation is:
[LDL] = [Total Cholesterol] – [HDL] – [(Triglycerides/5)]
Take your total cholesterol level, subtract the HDL, and subtract the triglycerides (that have been divided by 5).
The Friedewald formula is known to be quite inaccurate at extremes of triglycerides and total cholesterol [R]. The difference between measured and calculated LDL-C increases as the triglyceride level increases [R].