Creatinine Clearance: What it is and Reference Values
The creatinine clearance test is done to assess kidney function, which is done by comparing the concentration of creatinine in the blood with the concentration of creatinine present in the person's 24-hour urine sample. Thus, the result informs the amount of creatinine that was taken from the blood and eliminated in the urine, and as this process is carried out by the kidneys, changes in the results may be indicative of kidney damage.
Usually the creatinine clearance test is requested when a change in the concentration of creatinine in the blood is noticed, when there is an increase in the concentration of protein in the urine and to assist in the diagnosis of kidney and heart diseases. In addition, creatinine clearance can also be requested to monitor the evolution of some diseases, such as Congestive Heart Failure and Chronic Renal Failure, for example. Understand more about what creatinine is.
When the exam is requested
In addition to being requested when there is an excess of creatinine in the blood or a high concentration of protein in the urine, also called proteinuria, the creatinine clearance test is also usually requested when symptoms appear that may indicate kidney problems, such as:
- Swelling in the face, wrists, thighs or ankles;
- Urine with blood or foam;
- Marked decrease in the amount of urine;
- Constant pain in the kidney region.
Therefore, this test is also requested regularly when you have kidney disease, to assess the degree of progression of the disease and to understand how well your kidneys are functioning.
How to take the exam
To do the creatinine clearance test, you must collect urine for 24 hours and have a blood test at the beginning or end of that time. Both the collected blood and urine are sent to the laboratory for creatinine measurement in both materials. Here's how to do the 24-hour urine test.
The value of creatinine clearance is given by a mathematical formula that considers, in addition to the concentration of creatinine in blood and urine, the weight, age and sex of each person.
How to prepare
Although there is no specific preparation to take the creatinine clearance test, some laboratories recommend fasting for 8 hours or just avoiding the consumption of cooked meat, as the meat increases the levels of creatinine in the body.
What are the reference values
The normal values for creatinine clearance are:
- Children: 70 to 130 mL / min / 1.73 m²
- Women: 85 to 125 mL / min / 1.73 m²
- Men: 75 to 115 mL / min / 1.73 m²
When the clearance values are low, they may indicate kidney problems, such as kidney failure, heart failure, such as heart failure, or even be a consequence poor in meat, such as the vegetarian diet, for example. High values of creatinine clearance, in general, occur in pregnant women, after physical activity or even after eating large amounts of meat.