1. What is the Friedewald Formula?

The Friedewald formula is a widely used method for estimating LDL cholesterol (LDL-C) levels from total cholesterol (TC), HDL cholesterol (HDL-C), and triglyceride (TG) measurements. It provides a practical alternative to direct LDL measurement when resources are limited.

2. How Does the Calculator Work?

The calculator uses the Friedewald formula:

Where:

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

Explanation: The formula estimates LDL cholesterol by subtracting HDL cholesterol and one-fifth of triglycerides from total cholesterol.

3. Importance of LDL-C Calculation

Details: Accurate LDL-C estimation is crucial for assessing cardiovascular risk, guiding lipid-lowering therapy, and monitoring treatment effectiveness in patients with dyslipidemia.

4. Using the Calculator

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

5. Frequently Asked Questions (FAQ)

Q1: When is the Friedewald formula not accurate?
A: The formula becomes less accurate when triglyceride levels exceed 400 mg/dL, in patients with type III hyperlipoproteinemia, or with very low LDL levels.

Q2: What are the limitations of this calculation?
A: It assumes a fixed ratio of VLDL cholesterol to triglycerides (1:5), which may not hold true in all individuals, particularly those with hypertriglyceridemia.

Q3: Are there alternative methods for LDL calculation?
A: Yes, direct LDL measurement or the Martin-Hopkins equation may be used when triglycerides are elevated (>400 mg/dL).

Q4: What are optimal LDL cholesterol levels?
A: Generally, LDL-C below 100 mg/dL is desirable, but target levels depend on individual cardiovascular risk factors (may be as low as 70 mg/dL or lower for high-risk patients).

Q5: Should fasting samples be used?
A: Yes, for accurate results, blood samples should be collected after a 9-12 hour fast to minimize the effect of recent food intake on triglyceride levels.