Ammonia Test (24-Hour Urine / Plasma)
Purpose:
This test measures the amount of ammonia in either plasma (blood) or urine collected over 24 hours. It helps evaluate liver function, kidney disorders, and certain metabolic conditions.
Sample Types:
Plasma: A blood sample is collected using a special technique to prevent false readings.
24-Hour Urine: All urine passed in 24 hours is collected to determine how much ammonia the kidneys excrete.
Why the Test is Done:
To diagnose or monitor hepatic encephalopathy, a condition caused by poor liver function.
To assess urea cycle disorders (inherited conditions that affect nitrogen waste removal).
To evaluate metabolic acidosis or renal tubular acidosis.
To help explain confusion, lethargy, or coma when other causes are ruled out.
Normal Ranges (May vary by lab):
Plasma Ammonia: 15–45 µg/dL
Urine Ammonia (24-hr): Varies, often reported in mmol/day or mg/day depending on diet and health.
Precautions & Considerations:
Fasting may be required for accurate plasma results.
Avoid smoking and strenuous activity before the test.
Specimens must be handled properly (on ice, processed quickly) to avoid false elevation in plasma levels.
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