A mathematical equation is used to estimate the GFR. In addition to serum creatinine, other factors in the equation include age, race and gender. Sometimes, optional factors such as weight, blood urea nitrogen (BUN) and serum albumin are used to get the patient's GFR level. Once the GFR level is known the stage of kidney disease can be determined.
The glomerular filtration rate (GFR) is a good way to find out the patient's stage of kidney disease. The main factor in estimating the GFR is finding out the level of creatinine in the blood. Your doctor will order blood tests that will list your serum creatinine. This is a waste product that comes from muscle activity. When kidneys are functioning, they remove creatinine from the blood. As kidney function slows, blood levels of creatinine rise.