Table of ContentsView AllTable of ContentsPurpose of TestRisks and ContraindicationsBefore the TestDuring the TestAfter the TestResultsA Word From Verywell
Table of ContentsView All
View All
Table of Contents
Purpose of Test
Risks and Contraindications
Before the Test
During the Test
After the Test
Results
A Word From Verywell
Creatinine tests are used to measure the level of a waste product, known as creatinine, in your blood and urine. Creatinine is produced during the normal breakdown of muscle tissue, and because it is produced at a relatively steady rate, labs can use it as a marker to see how well your kidneys are functioning.
Creatinine tests are used to screen, diagnose, and monitor kidney (renal) disorders, includingchronic kidney diseaseandacute renal failure. They can also be used to evaluate how other diseases, such as heart and liver disease, impact the kidneys.
Creatinine tests may also be used to assess your response tokidney treatmentor to check that your kidneys are healthy prior to surgery.
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. They can be used as much for a routine health exam as for the diagnosis and monitoring of a disease.
How the Test Works
If your kidneys are functioning normally, creatinine will be excreted from the body in urine. If the kidneys are impaired, creatinine cannot be excreted as effectively and will begin to accumulate in the bloodstream.
Two different creatinine tests are used to determine the levels in your urine and blood:
Serum creatinine output is proportional to muscle mass, meaning that people with more muscle will have higher SCr readings. Similarly, strenuous physical activity can affect both SCr and CrCl readings, given than exercise results in more creatine being converted into energy.
Indications for Testing
Serum creatinine is included as part of a standard battery of tests known as the basic metabolic panel (BMP), which includes albumin,blood urea nitrogen (BUN), calcium, electrolytes (sodium, potassium, chloride, and bicarbonate), glucose, and phosphorus. The BMP can be used for screening purposes or to help diagnose a suspected kidney disorder.
With that being said, creatinine clearance is still routinely used for diagnostic purposes, especially when a24-hour urine volume testis needed for more comprehensive evaluation. The test may also provide more accurate insights if you have especially large muscle mass or a marked loss in muscle mass.
Conditions it Helps Diagnose
The creatinine tests can be used helpdiagnoseany number of kidney disorders, broadly described as either a chronic kidney disease or an acute kidney injury.
In some cases, CKD can lead toend-stage renal disease (ESRD)in which dialysis or a kidney transplant is needed to prevent death.
Acute kidney injury (AKI)refers to any condition that harms the kidneys and leads to impairment. Unlike CKD, an AKI is sometimes reversible.An AKI may be related to an injury or disorder situated before the kidneys (prerenal), in the kidneys (renal), or after the kidneys (postrenal).
Among the examples:
An AKI can also lead toacute renal failure, which in some casescan be reversedonce the underlying injury or disorder is treated.
Creatinine tests are safe and minimally invasive.
While there are no contraindications for either test, the creatinine clearance test may be impractical for people with acute urinary retention (the decreased ability to urinate).
Timing of Blood Test
You can take the serum creatinine blood test at any time of the day. If a creatinine clearance urine test is ordered alongside the serum creatinine, more planning is involved.
Timing of Urine Test
For a creatinine clearance urine test you need to get a special container from the lab to take home with you. Once the urine collection is complete, you must return the container as soon as possible the next day.
When picking up the collection kit from the lab, you will need to provide your ID and personal information so that a label with a generated code can be printed and placed on the collection container. Your insurance or payment details may also be taken so that you can drop the sample off at the lab without delay.
It is often best to perform the 24-hour urine collection on your day off so that you don’t have to transport the container from one place to the next. For schoolchildren, you may want to start the collection on a Sunday morning and drop the sample off at the lab on Monday morning.
Location
The blood tests can be performed at a healthcare provider’s office, clinic, hospital, or independent lab facility. Some walk-in facilities do not require an appointment.
The urine collection is performed at home. You will need to have a cool place, like a refrigerator or a portable ice chest, to keep the sample cool.
What to Wear
For the serum creatinine blood draw, either wear short sleeves or a top with sleeves that can be easily rolled up.
Food and Drink
Food restrictions are generally not required for either test. However, for the 24-hour urine collection, you may be asked to avoid alcohol the day before and during the test. You may also be asked to avoid strenuous exercise, which can affect your results.
Medications
While you generally do not need to stop taking medications for a serum creatinine blood test, you may be advised to do so for the 24-hour urine collection. This is because the aim of the urine test is to get an accurate representation of how your kidneys function devoid of any substances that influence filtration.
As such, it is important to advise a healthcare provider about any drugs you may be taking, whether they be prescription, over-the-counter, nutritional, traditional, or recreational.
Problematic drugs may include:
With that being said, never stop taking any medication without first speaking with a healthcare provider.
What to Bring
Be sure to bring your ID and health insurance cards with you when signing in at the lab.
Cost and Health Insurance
The cost of a serum creatinine blood tests will vary depending on the lab and its location. While insurance pre-authorization is generally not required, you may want to call in advance to find out how much yourcopay or coinsurancecosts will be.
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.
Other Considerations
If your child is undergoing the 24-hour urine collection, take extra care to explain the reasons for the test and why the samples cannot be missed. Younger children in particular can get easily distracted and forget.
If you turn the procedure into a game rather than a chore—rewarding the child with a gold star and grand prize for not missing a collection, for example—you may provide the incentive needed to keep your him focused.
You can either perform the urine collection first and have the blood test done when you drop off the sample or vice versa.
Blood Test
Pre-Test:On the day of the test, after signing in and confirming your insurance information, you will be taken to an examination room where your height and weight will be recorded. 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.
Post-Test:You will be free to go unless you feel lightheaded from the blood draw, in which case you may be asked to rest until you feel well.
BMI is a dated, flawed measure. It does not take into account factors such asbody composition, ethnicity, sex, race, and age. Even though it is a biased measure, BMI is still widely used in the medical community because it’s an inexpensive and quick way to analyze a person’s potential health status and outcomes.
24-Hour Urine Collection
Unless a healthcare provider tells you otherwise, the 24-hour collection will not begin until the morning. It is important to remember that you cannot miss a sample because the urine volume plays as much a part in the CrCl and eGFR calculations as the concentration of creatinine.
Throughout the Test:To collection procedure can vary slightly but generally involves the same basic steps.
Post-Test:Once the collection process is complete, the sealed containers need to be taken to the lab as soon as possible. If you are delayed for any reason, call the lab for instructions.
Interpreting the Results
The results of the creatinine tests can provide a very strong indication of how well your kidneys are functioning. The results are classified based on a reference range (RR) which delineates the range of numeric values considered normal for that test.
Anything above the upper end of the RR is considered abnormally high (often described on the report with the letter “H”). Similarly, anything below the lower end of the RR is considered abnormally low (described with the letter “L”).
The normal ranges for a serum creatinine (SCr) test are:
The normal ranges for a creatinine clearance (CrCl) test are:
The CrCl range in children is not so straightforward. It relies on one of several different algorithms that calculate the CrCl based on age, weight, height, and SCr.
Normal value ranges may vary slightly among different labs. Some use different algorithms or test different samples. As such, you should try to use the same lab whenever monitoring kidney function to ensure accurate comparative results.
Generally speaking, if yourcreatinine test results are high, you may have:
By contrast, if yourcreatinine test results are low, you may have:
Creatinine tests are valuable tools for evaluating kidney function and investigating the many possible causes of renal impairment. They are easy to use, minimally invasive, and are highly accurate if performed correctly.
Because the symptoms of renal impairment are often generalized and non-specific, ask a healthcare provider about a BMP if you experience some or all of the following symptoms:
12 SourcesVerywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read oureditorial processto learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.National Kidney Foundation.Tests to measure kidney function, damage and detect abnormalities.Ma Q, Gao Y, Lu J, et al.The effect of regular aerobic exercise on renal function in patients with CKD: A systematic review and meta-analysis.Front Physiol. 2022;13:901164. doi:10.3389/fphys.2022.901164Kildow BJ, Karas V, Howell E, et al.The utility of basic metabolic panel tests after total joint arthroplasty.J Arthroplasty. 2018;33(9):2752-2758. doi:10.1016/j.arth.2018.05.003Mann SJ, Gerber LM.Addressing the problem of inaccuracy of measured 24-hour urine collections due to incomplete collection.J Clin Hypertens (Greenwich). 2019;21(11):1626-1634. doi:10.1111/jch.13696National Institute of Diabetes and Digestive and Kidney Diseases.Glomerular diseases.Centers for Disease Control and Prevention.CKD-Related Health Problems.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).
12 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read oureditorial processto learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.National Kidney Foundation.Tests to measure kidney function, damage and detect abnormalities.Ma Q, Gao Y, Lu J, et al.The effect of regular aerobic exercise on renal function in patients with CKD: A systematic review and meta-analysis.Front Physiol. 2022;13:901164. doi:10.3389/fphys.2022.901164Kildow BJ, Karas V, Howell E, et al.The utility of basic metabolic panel tests after total joint arthroplasty.J Arthroplasty. 2018;33(9):2752-2758. doi:10.1016/j.arth.2018.05.003Mann SJ, Gerber LM.Addressing the problem of inaccuracy of measured 24-hour urine collections due to incomplete collection.J Clin Hypertens (Greenwich). 2019;21(11):1626-1634. doi:10.1111/jch.13696National Institute of Diabetes and Digestive and Kidney Diseases.Glomerular diseases.Centers for Disease Control and Prevention.CKD-Related Health Problems.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).
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read oureditorial processto learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
National Kidney Foundation.Tests to measure kidney function, damage and detect abnormalities.Ma Q, Gao Y, Lu J, et al.The effect of regular aerobic exercise on renal function in patients with CKD: A systematic review and meta-analysis.Front Physiol. 2022;13:901164. doi:10.3389/fphys.2022.901164Kildow BJ, Karas V, Howell E, et al.The utility of basic metabolic panel tests after total joint arthroplasty.J Arthroplasty. 2018;33(9):2752-2758. doi:10.1016/j.arth.2018.05.003Mann SJ, Gerber LM.Addressing the problem of inaccuracy of measured 24-hour urine collections due to incomplete collection.J Clin Hypertens (Greenwich). 2019;21(11):1626-1634. doi:10.1111/jch.13696National Institute of Diabetes and Digestive and Kidney Diseases.Glomerular diseases.Centers for Disease Control and Prevention.CKD-Related Health Problems.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).
National Kidney Foundation.Tests to measure kidney function, damage and detect abnormalities.
Ma Q, Gao Y, Lu J, et al.The effect of regular aerobic exercise on renal function in patients with CKD: A systematic review and meta-analysis.Front Physiol. 2022;13:901164. doi:10.3389/fphys.2022.901164
Kildow BJ, Karas V, Howell E, et al.The utility of basic metabolic panel tests after total joint arthroplasty.J Arthroplasty. 2018;33(9):2752-2758. doi:10.1016/j.arth.2018.05.003
Mann SJ, Gerber LM.Addressing the problem of inaccuracy of measured 24-hour urine collections due to incomplete collection.J Clin Hypertens (Greenwich). 2019;21(11):1626-1634. doi:10.1111/jch.13696
National Institute of Diabetes and Digestive and Kidney Diseases.Glomerular diseases.
Centers for Disease Control and Prevention.CKD-Related Health Problems.
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).
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