1. What is the Friedewald Formula?

The Friedewald formula is a widely used equation to estimate LDL cholesterol levels when a direct measurement is not available. It calculates LDL based on total cholesterol, HDL cholesterol, and triglyceride levels.

2. How Does the Calculator Work?

The calculator uses the Friedewald formula:

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 formula 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. Monitoring LDL levels helps assess cardiovascular risk and guide lipid-lowering therapy.

4. Using the Calculator

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

5. Frequently Asked Questions (FAQ)

Q1: When is the Friedewald formula not accurate?
A: The formula is less accurate when triglycerides exceed 400 mg/dL, in non-fasting samples, or in patients with certain conditions like diabetes or hypertriglyceridemia.

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: Are there alternatives to the Friedewald formula?
A: Yes, the Martin/Hopkins method and other equations may be more accurate in certain populations, especially those with low LDL or high triglycerides.

Q4: Should this be used for fasting or non-fasting samples?
A: Traditionally used with fasting samples, but recent guidelines suggest it can be used with non-fasting samples with some limitations.

Q5: Why divide triglycerides by 5?
A: This estimates VLDL cholesterol, as VLDL typically carries about 20% of triglycerides by weight (hence 1/5 or 0.20 ratio).