1. What is the Friedewald Equation?

The Friedewald equation is a formula used to estimate LDL cholesterol (low-density lipoprotein) levels in the blood without requiring direct measurement. It's widely used when a direct LDL measurement isn't available.

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 often called "bad cholesterol" because high levels can lead to plaque buildup in arteries and increase risk of heart disease and stroke.

4. Using the Calculator

Tips: Enter all values in mg/dL. The equation is valid only when triglycerides are below 400 mg/dL. For higher TG levels, direct LDL measurement is needed.

5. Frequently Asked Questions (FAQ)

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

Q2: What are normal LDL values?
A: Optimal 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 is the Friedewald equation not accurate?
A: When triglycerides are >400 mg/dL, in non-fasting samples, or with certain conditions like type III hyperlipoproteinemia.

Q4: Are there alternatives to the Friedewald equation?
A: Yes, the Martin/Hopkins method and direct LDL measurement are alternatives, especially when TG is high.

Q5: Should I fast before testing?
A: For most accurate results, a 9-12 hour fast is recommended before lipid panel tests.