BUN

The BUN (blood urea nitrogen) is a kind of nitrogen-containing compound in plasma, except protein, which is excreted from body by GFR. When the kidney failure function is damaged mildly, BUN may not change; But when GFR drops to below 50%, BUN will increase. For the patients with chronic kidney failure, the increasing level of BUN equals to severity of illness condition:

Compensation period of kidney failure: GFR will drop to 50 ml/min, BUN<9 mmol/L

Decompensation period of kidney failure: BUN >9 mmol/L;

Kidney failure period: BUN >20 mmol/L.