Estimate protein breakdown and nitrogen balance using 24-hour urine nitrogen data.
g/day
kg
Calculation Summary
Total Protein Catabolic Rate (PCR):–
Normalized PCR (nPCR):–
Interpretation:Please enter values to see the interpretation.
About Protein Catabolic Rate (PCR)
The Protein Catabolic Rate (PCR), also referred to as the Protein Nitrogen Appearance (PNA), is a clinical metric used to estimate the daily protein intake of a patient based on the amount of nitrogen they excrete. This is particularly vital in managing patients with chronic kidney disease (CKD) or those undergoing dialysis.
The Calculation Formula
This calculator utilizes the standard nitrogen balance formula:
PCR (g/day) = (UUN + 4) × 6.25
nPCR (g/kg/day) = PCR / Body Weight
Where UUN is the 24-hour Urine Urea Nitrogen in grams. The constant 4 accounts for non-urinary nitrogen losses (feces, skin, etc.), and 6.25 is the conversion factor based on the fact that protein is approximately 16% nitrogen.
Clinical Significance
In healthy individuals, nitrogen intake should equal nitrogen output. In clinical settings:
nPCR Range
Clinical Status
< 0.8 g/kg/day
Potential Protein Malnutrition
1.0 – 1.2 g/kg/day
Target for Dialysis Patients
> 1.4 g/kg/day
High Protein Intake / Catabolic State
Example Calculation
If a patient weighs 70 kg and has a 24-hour UUN of 10 grams:
Normalize for weight: 87.5 / 70 = 1.25 g/kg/day (nPCR).
function calculatePCR() {
var uun = parseFloat(document.getElementById('uunValue').value);
var weight = parseFloat(document.getElementById('bodyWeight').value);
var resultsDiv = document.getElementById('pcr-results');
var totalPcrSpan = document.getElementById('totalPcrResult');
var npcrSpan = document.getElementById('npcrResult');
var interpretationSpan = document.getElementById('pcrInterpretation');
if (isNaN(uun) || isNaN(weight) || uun <= 0 || weight <= 0) {
alert("Please enter valid positive numbers for both UUN and Body Weight.");
return;
}
// Formula: PCR = (UUN + 4) * 6.25
var totalPcr = (uun + 4) * 6.25;
// Formula: nPCR = PCR / weight
var npcr = totalPcr / weight;
// Update Display
totalPcrSpan.innerText = totalPcr.toFixed(2) + " g/day";
npcrSpan.innerText = npcr.toFixed(2) + " g/kg/day";
// Interpretation Logic
var interpretation = "";
if (npcr = 0.8 && npcr <= 1.3) {
interpretation = "The nPCR is within a standard clinical range for maintenance. This suggests adequate protein intake for most stable patients.";
} else {
interpretation = "The nPCR is high. This indicates high protein consumption or a hypercatabolic state (where the body is breaking down its own muscle mass rapidly).";
}
interpretationSpan.innerText = interpretation;
resultsDiv.style.display = "block";
// Scroll results into view
resultsDiv.scrollIntoView({ behavior: 'smooth', block: 'nearest' });
}