Creatinine is a waste product of muscular activity this is secreted into the blood stream. Because people's activity levels tend not to vary, serum creatinine levels remain constant in healthy people. Doctors monitor creatinine levels through routine blood work and use results as an important assessment tool. Together with blood urea nitrogen (BUN) and high urine protein, high creatinine levels can be a red flag for kidney disease. A careful diagnostic workup is important to determine why creatinine levels are high.
Kidney Disease
Diseased kidneys will no longer filter creatinine from the blood effectively; therefore, levels begin to rise. High creatinine is not a good marker for early stage kidney disease, however, because it does not begin to rise until about 40 percent of kidney function has already been lost.
Creatinine is also used to calculate the glomerular filtration rate, or GFR, in kidney patients. GFR is a measure of how effectively the kidneys filter blood. In his article "An Approach To The Evaluation Of An Elevated Serum Creatinine," Micah Thorp asserts that GFR is the gold standard for measuring the extent of kidney disease.
Doctors routinely measure creatinine several times a year in patients who are at risk for kidney failure. These patients often find it helpful to track their creatinine levels on a spreadsheet over time. By watching how their creatinine levels change, they may get a sense of how fast their kidney disease is progressing.
Dehydration
Medline Plus, a website of the National Institutes of Health, indicates that transient increases in creatinine can be caused by dehydration. Patients with one kidney such as transplant recipients or kidney donors seem to be particularly susceptible to the effect of dehydration on creatinine. It is very important to rule out dehydration as a possible cause of high creatinine in this population because patients may mistakenly believe that their remaining kidney is failing.
Heart Disease
High creatinine levels has been linked to atherosclerosis, or hardening of the arteries. Transient high levels of creatinine can also be caused by different types of heart surgery, such as aneurysm repair or stent insertion. It is important to rule out these causes when evaluating high creatinine levels.
