1. What is the Friedewald Formula?

The Friedewald formula is a widely used equation to estimate LDL cholesterol (LDL-C) levels from measured total cholesterol, HDL cholesterol, and triglyceride values. 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:

• \( LDL-C \) — Low-density lipoprotein cholesterol (mmol/L)
• \( TC \) — Total cholesterol (mmol/L)
• \( HDL-C \) — High-density lipoprotein cholesterol (mmol/L)
• \( TG \) — Triglycerides (mmol/L)

Explanation: The formula estimates LDL cholesterol by subtracting HDL cholesterol and VLDL cholesterol (estimated as TG/2.2) from total cholesterol.

3. Importance of LDL-C Calculation

Details: LDL cholesterol is a major risk factor for cardiovascular disease. Accurate estimation helps in risk assessment and guiding lipid-lowering therapy decisions.

4. Using the Calculator

Tips: Enter all values in mmol/L. Ensure triglyceride levels are below 4.5 mmol/L for accurate results. All values must be positive numbers.

5. Frequently Asked Questions (FAQ)

Q1: When is the Friedewald formula not accurate?
A: The formula is less accurate when triglyceride levels exceed 4.5 mmol/L, in non-fasting samples, or in certain medical conditions.

Q2: What are normal LDL-C values?
A: Optimal LDL-C is generally <2.6 mmol/L, though target levels vary based on individual cardiovascular risk factors.

Q3: Why divide triglycerides by 2.2?
A: This factor estimates VLDL cholesterol, as VLDL typically carries about 45% of triglyceride mass (hence 1/2.2 ≈ 0.45).

Q4: Are there alternative formulas?
A: Yes, newer formulas like the Martin-Hopkins equation may provide better accuracy, especially at very low LDL or high triglyceride levels.

Q5: Should fasting samples be used?
A: Yes, for most accurate results, blood should be drawn after a 9-12 hour fast to minimize triglyceride variability.