1. What is the NKF Creatinine Clearance Formula?

The NKF (National Kidney Foundation) recommended formula estimates creatinine clearance (CrCl) from serum creatinine, age, weight, and sex. It's commonly used for drug dosing adjustments in patients with kidney impairment.

2. How Does the Calculator Work?

The calculator uses the NKF formula:

Where:

• \( Scr \) — Serum creatinine (mg/dL)
• \( age \) — Age in years
• \( weight \) — Weight in kilograms
• 0.85 — Female multiplier

Explanation: The equation estimates the rate at which creatinine is cleared from the blood by the kidneys, which correlates with kidney function.

3. Importance of CrCl Calculation

Details: Creatinine clearance is crucial for medication dosing adjustments in patients with impaired kidney function, particularly for drugs that are renally excreted.

4. Using the Calculator

Tips: Enter serum creatinine in mg/dL, age in years, weight in kg, and select gender. All values must be valid (creatinine > 0, age between 1-120, weight > 0).

5. Frequently Asked Questions (FAQ)

Q1: What's the difference between CrCl and eGFR?
A: CrCl estimates actual creatinine clearance, while eGFR estimates glomerular filtration rate. CrCl is often higher than eGFR.

Q2: What are normal CrCl values?
A: Normal is approximately 95-125 mL/min for men and 85-115 mL/min for women. Values decline with age.

Q3: When should creatinine be measured?
A: Morning fasting sample is ideal, but random samples are acceptable. Avoid testing after meat-heavy meals or vigorous exercise.

Q4: Are there limitations to this formula?
A: Less accurate in extremes of age, obesity, muscle wasting, amputees, and those with rapidly changing kidney function.

Q5: Why is weight included in this formula?
A: Creatinine production is proportional to muscle mass, which correlates with body weight.