Creatinine is a breakdown product of creatine, an energy compound concentrated in the skeletal muscle. Because creatinine is removed by your kidneys, the levels of creatinine in your blood and urine can indicate the status of your kidney function. As kidney function deteriorates, blood creatinine tends to rise and the urinary removal of creatinine may become inefficient.
When to Test for Creatinine
Creatinine tests, which measure blood and sometimes urinary creatinine, are a common part of the basic or comprehensive metabolic panel included in a routine physical exam. They aid in the diagnosis of an unknown illness. If you have an underlying disease such as diabetes or hypertension that can affect the kidneys, your doctor may order a creatinine test to monitor your kidney function, according to Lab Tests Online. A creatinine test sometimes precedes a medical procedure known to stress or damage the kidneys. For example, computed tomography or CT often requires drugs that can damage the kidneys and may require a creatinine test to screen for kidney abnormalities.
Test Result
A health condition that compromises kidney function, e.g. heart disease, diabetes, infection, autoimmune disease, prostate disease or kidney diseases like kidney stones and kidney damage, can increase the level of blood creatinine. Thus, increased blood creatinine suggests such a disease, according to Lab Tests Online. People with muscle injury may also have increased serum creatinine because of muscle breakdown. Low creatinine is less common and usually not a concern. Pregnancy and low muscle mass may cause blood creatinine to decrease. The Foundation for IgA Nephropathy cautions that blood creatinine often does not rise until the kidney function has decreased by half. To detect early-stage kidney disease, your doctor may evaluate the estimated glomerular filtration rate, which is calculated based on the blood creatinine but more reliably detects early kidney dysfunctions, rather than the creatinine test result by itself.
Creatinine Level and Diet
Despite common belief, diet does not significantly affect the blood level of creatinine, according to the Foundation for IgA Nephropathy. However, a diet rich in meat can sometimes increase the filtration or removal of creatinine by the kidneys and increase the creatinine clearance, which is based on the ratio of 24-hour urinary excretion of creatinine and blood creatinine. Meat contains creatine, which is metabolized to creatinine and removed by the kidneys as the creatine in the muscles. In general, if you follow a high-meat or high-protein diet, your creatinine test result, especially the creatinine clearance rate, may vary to a certain extent. But the general trend over time usually does not change significantly.
Creatinine Level and Dehydration
Dehydration reduces the blood flow to your kidneys and interferes with the removal of blood creatinine. Dehydration also directly increases blood creatinine as the loss of water concentrates the substances in the blood. If you exercise intensively, drink water or carbohydrate-containing sports drinks before, during and after exercise to prevent dehydration, especially in hot and humid environment. Stay adequately hydrated before a creatinine test to avoid false positives.
