| undetermined nitrogen | The nitrogen of blood, urine, etc., other than urea, uric acid, amino acids, etc., that can be directly estimated; in blood it amounts to about 25 mg per 100 ml. Urea nitrogen, the portion of nitrogen in a biological sample, such as blood or urine, that derives from its content of urea. See: blood urea nitrogen. (05 Mar 2000) |
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