blood urea nitrogen level plasma urea nitrogen level 2011-11-02T04:23:54Z BUN level CMO:0000586 The level of urea in terms of nitrogen content measured in a specific volume of plasma, the fibrinogen-containing fluid portion of the blood in which the particulate components are suspended.The plasma urea nitrogen level is converted to urea concentration by multiplying by 60/28 or 2.14. Urea is the chief nitrogenous end product of protein metabolism in whole blood. Urea is formed in the liver from amino acids and from ammonia compounds and can be found in urine, blood, and lymph. VT:0005265 clinical_measurement_ontology mshimoyama