1. What is the LDL Calculation?

The Friedewald formula estimates LDL cholesterol (LDL-C) from total cholesterol (TC), HDL cholesterol (HDL-C), and triglycerides (TG). It's widely used when direct LDL measurement isn't available.

2. How Does the Calculator Work?

The calculator uses the Friedewald formula:

Where:

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

Explanation: The formula estimates VLDL cholesterol as TG/5 (assuming VLDL-C is about 20% of TG) and subtracts both HDL and VLDL from total cholesterol to get LDL.

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 treatment decisions.

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 needed.

5. Frequently Asked Questions (FAQ)

Q1: Why divide triglycerides by 5?
A: This estimates VLDL cholesterol, which typically carries about 20% of the triglyceride value (hence dividing by 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 this formula not accurate?
A: When TG >400 mg/dL, in non-fasting samples, or in patients with type III hyperlipoproteinemia (dysbetalipoproteinemia).

Q4: Are there newer formulas than Friedewald?
A: Yes, the Martin/Hopkins equation adjusts the TG/VLDL ratio dynamically and may be more accurate, especially at low LDL and high TG levels.

Q5: Should this be used for everyone?
A: For most people with TG <400 mg/dL it's adequate, but direct measurement may be preferred in certain clinical situations.