LDL Cholesterol Calculator

What is the Friedewald Formula?

The Friedewald formula is a widely used method to estimate the concentration of low-density lipoprotein cholesterol (LDL-C) in the blood. It calculates LDL-C indirectly using results from a standard lipid panel.

The formula is: LDL-C = Total Cholesterol - HDL-C - (Triglycerides / 5). The (Triglycerides / 5) component is used as an estimate for very-low-density lipoprotein (VLDL) cholesterol.

Why is it Used?

• It provides a simple, cost-effective way to estimate LDL-C without the need for direct measurement.
• LDL-C is a primary marker for assessing cardiovascular disease risk.
• It is sufficient for routine screening and management in most patients.

Reference Values (ESC/EAS 2019)

• Low Risk: Target < 1.0 g/L (< 2.6 mmol/L)
• Moderate Risk: Target < 1.0 g/L (< 2.6 mmol/L)
• High Risk: Target < 0.7 g/L (< 1.8 mmol/L)
• Very High Risk: Target < 0.55 g/L (< 1.4 mmol/L)
• Extreme Risk: Target < 0.4 g/L (< 1.0 mmol/L)

Limitations of the Formula

While useful, the Friedewald formula has important limitations:

• Inaccuracy: The formula becomes inaccurate when triglyceride levels are high (typically > 4 g/L).
• Non-Fasting State: It should not be used on non-fasting blood samples.
• Certain Dyslipidemias: It may be inaccurate in patients with certain types of dyslipidemia.
• Direct Measurement: In critical cases, a direct LDL-C measurement is preferred.