Other conditions, such as heart failure, dehydration, and liver disease (cirrhosis), can also cause low creatinine clearance results. ??? Low BUN-to-creatinine ratio A low BUN-to-creatinine ratio may be associated with a diet low in protein, a severe muscle injury called rhabdomyolysis, pregnancy, cirrhosis, or syndrome of inappropriate antidiuretic hormone secretion (SIADH).