What is the difference between BUN and creatinine?

Blood urea nitrogen (BUN) and creatinine are both waste products filtered by the kidneys and used as indicators of kidney function. BUN is a measure of the amount of nitrogen in the form of urea present in the blood, while creatinine is a waste product generated by muscle metabolism. The key difference between BUN and creatinine lies in their sources and the factors that can affect their levels. BUN can be influenced by various factors, including protein intake, liver function, gastrointestinal bleeding, and dehydration. Creatinine levels, on the other hand, are primarily influenced by muscle mass and remain relatively stable over time. While both BUN and creatinine are used to assess kidney function, creatinine is considered a more reliable indicator because it is less affected by factors other than kidney function.