Creatinine tests are among the first tests a healthcare provider will turn to evaluate kidney function.
They are fast, easy to use, and relatively inexpensive to perform.
How the Test Works
The body continuously produces creatinine in the course of everyday functioning.
Illustration by Emily Roberts, Verywell
It is created when a substance called creatine, found primarily in muscles, is converted into energy.
Creatinine is a by-product of that process.
If your kidneys are functioning normally, creatinine will be excreted from the body in urine.
The BMP can be used for screening purposes or to help diagnose a suspected kidney disorder.
Chronic kidney disease (CKD)describes the progressive and non-reversible impairment of renal function.
Acute kidney injury (AKI)refers to any condition that harms the kidneys and leads to impairment.
Risks and Contraindications
Creatinine tests are safe and minimally invasive.
Before the Test
There are no preparations needed for a serum creatinine blood test.
If a creatinine clearance urine test is ordered alongside the serum creatinine, more planning is involved.
Once the urine collection is complete, you must return the container as soon as possible the next day.
Some walk-in facilities do not require an appointment.
The urine collection is performed at home.
Food and Drink
Food restrictions are generally not required for either test.
You may also be asked to avoid strenuous exercise, which can affect your results.
If you are uninsured, shop around for prices.
Generally speaking, independent labs have lower costs.
Some of the larger labs may even offer tiered pricing if you meet certain income qualifications.
Ask about patient assistance programs designed to help low-income families.
Younger children in particular can get easily distracted and forget.
This will later be used to calculate yourbody mass index (BMI)for the eGFR.
Other information will also be collected and will also factor into the analysis.
Throughout the Test:The blood draw, done by aphlebotomist, is performed as follows.
BMI is a dated, flawed measure.
It does not take into account factors such asbody composition, ethnicity, sex, race, and age.
24-Hour Urine Collection
Pre-Test:Gather the collection supplies provided to you by the lab.
You will should also have a preprinted form to record the time and date of each urination.
Unless a healthcare provider tells you otherwise, the 24-hour collection will not begin until the morning.
Throughout the Test:To collection procedure can vary slightly but generally involves the same basic steps.
If you are delayed for any reason, call the lab for instructions.
Normal value ranges may vary slightly among different labs.
Some use different algorithms or test different samples.
They are easy to use, minimally invasive, and are highly accurate if performed correctly.
Kaiser Permanente.Creatinine and creatinine clearance tests.
2019;21(11):1626-1634. doi:10.1111/jch.13696
National Institute of Diabetes and Digestive and Kidney Diseases.Glomerular diseases.
Johns Hopkins Medicine.End state renal disease.
National Kidney Foundation.Acute kidney injury (AKI).
National Kidney Foundation.Sudden loss of kidney function: Do you know what to do in this emergency?
National Kidney Foundation.5 drugs you may need to avoid or adjust if you have kidney disease.
BMJ Best Practice.Assessment of elevated creatine.
University of Rochester Medical Center.Creatinine clearance.
University of Rochester Medical Center.Creatinine (blood).
