Creatinine is a waste product present in the blood and urine. Creatine is created when food transforms into energy during the metabolic process. Creatine is then broken down into creatinine and taken out of the blood by the kidneys and passed from the body through the urine. The kidneys are vital organs and help keep the blood clean and well balanced. If the body is not capable of removing the waste, it will build up and damage the body and health of the blood.
Creatinine and the Liver
Creatinine levels show how well the body is able to process creatinine. If a creatinine level is too high or too low, it is important to have a physician examine kidney and liver function. Creatinine and Creatinine BUN ratio tests help determine whether the liver and kidneys are working normally.
Normal Creatinine Levels
According to the National Institutes of Health, a normal value of creatinine is .8 to 1.4 mg/dL. Some labs have their own measurement system for creatinine levels, but values and measurement levels are printed on lab results. Many labs also flag a value that is too high or too low to ensure a physician sees it. Women normally have lower creatinine values than men because of the difference in muscle mass. Slightly elevated ranges are normally a sign that the kidneys are not as productive as they should be, and that the organs should be closely monitored and re-tested.
To measure creatinine levels, blood and urine samples will be taken. The urine samples are taken over a 24-hour period. It is important not to exercise before the creatinine test, as strenuous exercise can cause the creatinine level to rise.
High Creatinine Level
High creatinine levels exceed 1.5 mg/dL and often indicate serious kidney damage, which may be due to low blood flow, shock, cancer or a life-threatening infection. Conditions that often produce high creatinine levels consist of urinary tract blockages, cardiac problems, thyroid problems or dehydration.
Low Creatinine Level
Low levels of creatinine fall under .8 mg/dL. Low creatinine levels in the blood can indicate a possible muscular disease, such as muscular dystrophy. Low levels can also show the effects of aging or that something needs evaluation in a person’s diet. If a person has a diet low in protein, creatinine levels may be adversely affected.
Creatinine levels are evaluated during pregnancy, as pregnancy can sometimes cause low blood creatinine. In this case, a treatment plan may be necessary and would include evaluation of the pregnancy's stress on the kidneys.
Low levels can also be due to cancer, low blood flow to the kidneys, urinary problems, cirrhosis of the liver or dehydration.
BUN to Creatinine Ratio
If a physician suspects liver damage, she will evaluate the BUN-to-creatinine level. This test considers both liver and kidney function through a comparison of levels. BUN is an acronym for blood urea nitrogen; the evaluation tests urea, which is a waste product of proteins broken down in the body. It is made in the liver and passed through urine.
A BUN and creatinine ratio test might indicate whether a rise in level is occurring because of acute kidney failure, shock or dehydration. A high ratio can signal bleeding in the digestive or respiratory systems. On the contrary, if there is a low BUN to creatinine ratio, a physician will consider hormones, dietary issues, muscle injury, pregnancy, liver problems, lung disease or other problems with the central nervous system. If the levels are out of the normal range, a physician will evaluate family health history, run additional tests and reconsider what medications a person is taking. If the test shows high or low ranges, another test is normally reordered within two weeks.