1. What is the Friedewald Equation?

The Friedewald equation is a formula used to estimate LDL cholesterol levels from a standard lipid panel without requiring direct measurement. It's widely used in clinical practice when triglycerides are below 400 mg/dL.

2. How Does the Calculator Work?

The calculator uses the Friedewald equation:

Where:

• \( LDL \) — Low-density lipoprotein cholesterol (mg/dL)
• \( TC \) — Total cholesterol (mg/dL)
• \( HDL \) — High-density lipoprotein cholesterol (mg/dL)
• \( TG \) — Triglycerides (mg/dL)

Explanation: The equation estimates LDL 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 guide treatment decisions and monitor response to lipid-lowering therapy.

4. Using the Calculator

Tips: Enter values from a standard lipid panel (TC, HDL, TG in mg/dL). The equation is not valid when triglycerides exceed 400 mg/dL.

5. Frequently Asked Questions (FAQ)

Q1: Why divide triglycerides by 5?
A: This estimates VLDL cholesterol, as VLDL typically carries about 20% of triglycerides by weight (hence 1/5 ratio).

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

Q3: When is direct LDL measurement needed?
A: When triglycerides >400 mg/dL, with certain genetic disorders, or when more precise measurement is clinically necessary.

Q4: Are there limitations to this equation?
A: Less accurate with non-fasting samples, very high TG, diabetes, or certain medications that alter lipid metabolism.

Q5: Are there alternative equations?
A: Yes, newer equations like Martin/Hopkins may be more accurate in some populations, especially when LDL is very low.