Urea and creatinine are both indicators of kidney function. Urea nitrogen is a small molecule toxin produced mainly by protein catabolism. If there is an increase in urea nitrogen, it often indicates renal insufficiency, but because urea nitrogen is metabolized by protein catabolism, it is also influenced by diet and other conditions. For example, if we eat a lot of protein, or if we have this kind of gastrointestinal bleeding, the increase of hemoglobin decomposition will also lead to the increase of urea nitrogen. Creatinine is divided into blood creatinine and urine creatinine, blood creatinine is also an indicator from blood sampling, it is the product of muscle metabolism. If we have renal insufficiency, blood creatinine will often rise, while on the contrary, urine creatinine will fall.