1. What is the Friedewald Equation?

The Friedewald equation estimates LDL cholesterol (LDL-C) from total cholesterol (TC), HDL cholesterol (HDL-C), and triglycerides (TG). It provides a practical method for LDL estimation when direct measurement is not available.

2. How Does the Calculator Work?

The calculator uses the Friedewald equation:

Where:

• \( TC \) — Total cholesterol (mg/dL)
• \( HDL-C \) — HDL cholesterol (mg/dL)
• \( TG \) — Triglycerides (mg/dL)

Explanation: The equation estimates LDL cholesterol by subtracting HDL and VLDL (estimated as TG/5) from total cholesterol.

3. Importance of LDL Calculation

Details: LDL cholesterol is a major risk factor for cardiovascular disease. Accurate estimation helps assess cardiovascular risk and guide treatment decisions.

4. Using the Calculator

Tips: Enter total cholesterol, HDL cholesterol, and triglycerides in mg/dL. All values must be valid (>0). Note: This equation is not valid when TG > 400 mg/dL.

5. Frequently Asked Questions (FAQ)

Q1: When is the Friedewald equation not accurate?
A: The equation is less accurate when triglycerides exceed 400 mg/dL, in non-fasting samples, or in patients with certain metabolic disorders.

Q2: What are normal LDL values?
A: Optimal LDL is <100 mg/dL, near optimal is 100-129 mg/dL, borderline high is 130-159 mg/dL, high is 160-189 mg/dL, and very high is ≥190 mg/dL.

Q3: When should lipid panel be measured?
A: Fasting for 9-12 hours is recommended for accurate triglyceride measurement, which affects LDL calculation.

Q4: Are there alternative equations?
A: Yes, the Martin/Hopkins equation and Sampson equation provide alternatives, especially when triglycerides are elevated.

Q5: Should this be used for treatment decisions?
A: While useful for screening, clinical decisions should be based on multiple factors including direct LDL measurement when appropriate.