High BUN-to-creatinine ratios occur with sudden (acute) kidney failure. This may be caused by shock or severe dehydration. A very high BUN-to-creatinine ratio may be caused by bleeding in the digestive tract.
Low blood creatinine levels can mean lower muscle mass caused by a disease, such as muscular dystrophy, or by aging. Low levels can also mean some types of severe liver disease or a diet very low in protein. Pregnancy can also cause low blood creatinine levels.
Low creatinine clearance levels can mean you have chronic kidney disease or serious kidney damage. Kidney damage can be from conditions such as a life-threatening infection, shock, cancer, low blood flow to the kidneys, or urinary tract blockage. Other conditions, such as heart failure and dehydration, can also cause low creatinine clearance levels.
Low BUN-to-creatinine ratios may be linked with a diet low in protein, a severe muscle injury called rhabdomyolysis, pregnancy, cirrhosis, or syndrome of inappropriate antidiuretic hormone secretion (SIADH). SIADH sometimes occurs with lung disease, cancer, diseases of the central nervous system, or the use of certain medicines.
What Affects the Test
You may not be able to have the test, or the results may not be helpful, if: