The creatinine clearance test is a combination of a blood test and a urine test. Creatinine is a waste product made by the body that is removed from the body by the kidneys. In this test, the level of creatinine present in the blood and urine is checked during a 24-hour period. With the help of the results, the level of creatinine made in the blood and the level of creatinine excreted in the urine is checked.
The amount of creatinine produced depends on the body’s muscle mass (muscle density). On the other hand, the removal of creatinine from the blood depends on the filtering capacity of the kidney, along with this it depends on how much and at what rate the amount of filtered blood per minute is referred to as the glomerular filtration rate (GFR). Therefore, a decrease in GFR suggests that kidney function has also slowed down.
When a kidney disease or disorder is suspected, a creatinine clearance test is done to check kidney function.
Signs and symptoms of kidney disease include:
- Swelling around the abdomen, face, ankles, and wrists
- Passing less urine
- Frothy, coffee-colored or bloody urine
- Urinary problems and decreased urination
- Protein in urine
- High blood pressure
- Nausea
- Vomiting
- Muscle cramps
- Itching and rashes on the skin
- Lack of sleep
This test is done for those people who have any disease related to chronic kidney disease or congestive heart failure. With its help, the growth and severity of these diseases are checked. This test also detects whether the patient needs dialysis or not.
How is a creatinine clearance test done?
For this test, a urine sample is stored for 24 hours. Blood samples are not taken during this 24-hour period. The sample is taken either before or after urine is collected.
This is a simple blood test that only takes about five minutes. The doctor takes a blood sample by inserting a needle into a vein in your arm. A small amount of blood is drawn into a sample tube. A person may also feel a slight pain or sting due to the needle being inserted.
It is necessary to measure the height and weight of the patient for accurate calculation.
To collect a 24-hour urine sample, you will need to collect samples as many times as you pass urine during the day. Except for the first urine of the day, all the urine till the next morning will be collected in a container.
There is no serious risk associated with this test except dizziness and bruising at the injection site. Occasionally an infection may occur at the injection site.
Creatinine clearance is measured in milliliters per minute (mL/min).
What is the normal creatinine clearance?
Normal levels of creatinine clearance differ in women and men. The normal range is 97–137 mL/min for men, 88–128 mL/min for women, and 40–65 mL/min for newborns. After age 40, creatinine clearance decreases by 6.5 mL/min every ten years.
What level of creatinine clearance indicates kidney failure?
Lower than normal levels of creatinine clearance test may be due to:
- Kidney failure
- Kidney damage
- Reduced blood flow to the kidneys
- Severe dehydration (loss of body fluids)
- Urinary tract obstruction
- Congestive heart failure
- Glomerulonephritis (due to infection or autoimmune disorder)
- Pyelonephritis (kidney infection caused by bacteria)
- Shock
- Diabetes
Certain drugs such as aminoglycosides, cisplatin, cephalosporins, and cimetidine are known to decrease the level of creatinine clearance. Creatinine clearance levels also decrease with age because GFR also decreases with age.