How is urea concentration calculated from BUN?

To understand how urea concentration is calculated from Blood Urea Nitrogen (BUN), it is essential to recognize the relationship between BUN and urea itself. BUN measures the amount of nitrogen in the blood that comes from urea, which is produced from protein metabolism.

In clinical practice, BUN levels are generally expressed in milligrams per deciliter (mg/dL), and the molecular weight of urea is approximately 60.06 g/mol, while that of nitrogen is about 14.01 g/mol. Since each molecule of urea contains two nitrogen atoms, the conversion factor between BUN and urea is derived from the ratio of their molecular weights.

The formula to convert BUN to urea concentration involves multiplying the BUN value by the conversion factor, which approximates to 2.14. This factor represents the conversion from the nitrogen component measured in BUN to the total urea concentration.

Therefore, multiplying BUN by 2.14 accurately reflects this relationship, yielding the urea concentration in the same unit (mg/dL). This calculation is essential in clinical settings for assessing renal function and protein metabolism.