Creatinine is a waste product that comes from the normal wear and tear on muscles of the body. Everyone has creatinine in their bloodstream.
That depends on your age, race, gender, and body size.
Looking at how much creatinine is in your blood is not the best way to
check your kidney health. That’s because the level of creatinine in your
blood is affected by your age, race, gender, and body size. (In other
words, what’s considered “normal” depends on these factors.) The best
way to know if your kidneys are working properly is by looking at your
glomerular filtration rate (GFR).
GFR is a routine lab that can be found on your blood work report. GFR is
a calculation that includes your creatinine, along with your age,
gender, race, and weight. Your GFR number will help your healthcare
provider know if you have kidney disease.
You may have kidney disease if your GFR number is:
Below 60 for three months
Above 60 with signs of kidney damage (having protein in the urine is a sign of kidney damage)
When your kidneys are working well, they filter out wastes and excess
fluid that become part of the urine your body makes each day. When
kidneys aren’t working well, you do not remove enough wastes and fluids
to keep you healthy. You also cannot make important hormones for your
blood and bones. Your GFR number is an estimate of how well your kidneys
are working and keeping you healthy.
If your GFR number is low, your kidneys are not working as well as they
should. Early detection will allow for early treatment. Early treatment
may keep kidney disease from getting worse.
Having a simple blood test for creatinine is the first step in checking your GFR. Creatinine is a waste product made by your body’s muscles. Your kidneys usually keep the level of creatinine just right. The level of creatinine in your blood and your age, race and gender are used to estimate your GFR.
Your doctor or testing lab usually calculates your GFR number. Be sure to talk with your doctor about the result.
In adults, the normal GFR number is more than 90. For more information, see chart on the bottom of page 2.
If your GFR is between 60 and 89.
People with mildly low GFR (between 60 and 89) may not have kidney
disease if there is no sign of kidney damage, such as protein in their
urine. These people should have their GFR checked more often. They may
be asked to avoid medications that can damage the kidneys (such as
ibuprofen) or reduce the dose of medicines that are removed by the
kidneys.
If there is kidney damage, such as protein in the urine, a result
between 60 and 89 may mean early kidney disease. Even a GFR over 90 with
protein in the urine is a sign of kidney disease. GFR must remain low
for three months for CKD to be diagnosed.
If your GFR is below 60
When GFR is below 60 for more than three months, this is moderate-to severe chronic kidney disease. You may be referred to a nephrologist (kidney doctor) for evaluation and treatment.
If your GFR is below 15
A GFR below 15 means kidney failure. If kidney failure occurs, dialysis or a kidney transplant will be needed to survive.
GFR gets lower with age, even in people without kidney disease. The older you are, the lower your GFR. The GFR calculation accounts for age. At any age, a GFR below 60 for three months or more indicates kidney disease.
More tests will be done to understand why it is low. The results of these tests may provide clues about what is happening. Examples of tests that might be ordered are:
- • Urine tests that look for:
- • The type and amount of protein (a sign of kidney damage)
- • Red blood cells (a sign of bleeding in the urinary system)
- • White blood cells (a sign of infection)
- • Ultrasound or CT scan to get a picture of your kidneys and urinary system. These pictures show the size of your kidneys and whether or not tumors, kidney stones, or cysts are present.
- • A biopsy to remove a tiny piece of the kidney for evaluation. The sample is studied under a microscope to see what kind of kidney damage is happening.
Some people are more likely than others to develop kidney disease. You may be at increased risk for kidney disease if you:
- • Have diabetes
- • Have high blood pressure
- • Have a family history of kidney disease
- • Are over 60 years of age
- • Are African American, Hispanic, Asian or American Indian