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Calcimator

Nitrogen Balance Calculator

Calculate nitrogen balance from protein intake and 24-hour urinary urea nitrogen (UUN). Determine if a patient is in anabolic or catabolic state and find protein targets.

Inputs

Results

Nitrogen balance (g N/day)

-1.2

Nitrogen intake (g N/day)12.8
Total nitrogen output (g N/day)14
Protein for equilibrium (g/day)88
Protein for anabolism (g/day)113
Current protein (g/kg/day)1.14
Target protein for anabolism (g/kg/day)1.61
Status (0-3)1
How to Use This Calculator
  1. Enter the patient's daily protein intake in grams.
  2. Input the 24-hour Urinary Urea Nitrogen (UUN) from a timed urine collection.
  3. Enter insensible nitrogen losses (default 4 g/day is a common clinical estimate).
  4. Enter weight in kg for context.
  5. Review nitrogen balance — positive values indicate anabolism; negative values indicate catabolism.

How the result changes with Daily protein intake (g)

Daily protein intake (g)Nitrogen balance (g N/day)
50-6
17514
32538
45058

What each input means

Daily protein intake (g)
Total grams of protein consumed per day.
24-hr Urinary Urea Nitrogen (g)
Measured from a 24-hour urine collection.
Insensible N losses (g)
Non-urinary nitrogen losses (fecal, skin). Standard estimate is 4 g/day.
Body weight (kg)
Current body weight for per-kg protein targets.

What each result means

Nitrogen balance (g N/day)
Positive = anabolic, negative = catabolic. Clinical target: +2 to +4.
Nitrogen intake (g N/day)
Protein intake divided by 6.25.
Total nitrogen output (g N/day)
UUN + insensible losses.
Protein for equilibrium (g/day)
Protein needed to achieve zero nitrogen balance.
Protein for anabolism (g/day)
Protein needed for +4 g N positive balance.
Current protein (g/kg/day)
Current protein intake per kilogram body weight.
Target protein for anabolism (g/kg/day)
Protein per kg needed for positive balance.
Status (0-3)
0 = severely catabolic, 1 = mildly catabolic, 2 = equilibrium/mildly anabolic, 3 = strongly anabolic.

How this is calculated

Worked example, using the default values

  1. Identify Input Parameters
    4 parameters
    Daily protein intake (g) = 80, 24-hr Urinary Urea Nitrogen (g) = 10, Insensible N losses (g) = 4, Body weight (kg) = 70 = 4 input(s) provided
  2. Calculate Nitrogen balance
    Nitrogen balance = nitrogenIntake - totalNitrogenOutput
    -1.2 = -1.2
  3. Calculate Nitrogen intake
    Nitrogen intake = proteinIntake / 6.25
    12.8 = 12.8
  4. Calculate Total nitrogen output
    Total nitrogen output = uun24hr + insensibleLoss
    14 = 14

Engine last updated . Checked against 1 independently-derived test — how we verify calculators.

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