Your kidneys are constantly working to remove toxins and waste products from your body and maintain your fluid balance. The purpose of a creatinine lab test is to determine whether your kidneys are functioning properly, but there are many factors that can alter the results of this test.

Keep reading to learn more about creatinine and normal kidney function levels.

What is creatinine?

In order to understand what creatinine tells you, first we need to know what creatinine is. According to the National Kidney Foundation, creatinine is a waste product of your body which comes from the normal wear and tear process that your muscles naturally go through every day as they produce energy and movement.

Everyone has some creatinine in their bloodstream; however, abnormally high creatinine serum levels can be a sign of an underlying disease.

How to check creatinine levels

Creatinine levels can be measured through a blood or urine test. Creatinine may be offered as part of routine lab testing, but it can also be part of a more comprehensive metabolic testing panel.

A simple blood sample is taken to measure your serum creatinine levels. According to the Mayo Clinic, you don’t need to do extensive preparation before a blood creatinine test. However, your healthcare provider may ask you to fast overnight before having your sample taken.

If you’re getting a urine creatinine test done, your doctor could ask you to collect urine over a period of 24 hours. With any type of creatinine test, you’ll probably have to avoid consuming large amounts of meat or creatine supplements before taking the test, since this can alter your creatinine lab values.

What is the normal creatinine level?

Normal creatinine lab values will depend on different factors. But according to Mount Sinai, creatinine reference ranges are as follows:

0.7-1.3 mg/dL (61.9 to 114.9 µmol/L) for adult men
0.6-1.1 mg/dL (53 to 97.2 µmol/L) for adult women

You should always discuss your creatinine test results with your healthcare provider to understand their meaning.

Why should you check creatinine levels?

A creatinine test can be used to assess your kidney health. But on their own, creatinine lab values can’t determine whether you have a decreased or elevated kidney function. That’s because your normal kidney function levels can vary widely depending on different factors, such as:

Age
Gender
Ethnicity
Body size
Diet
Nutritional status
Chronic illness
Dehydration
Kidney infections
High intensity exercise

Because of this, your healthcare provider will likely take your creatinine lab values into consideration along with other findings, such as your symptoms, medical history, and other lab test results in order to determine your kidney function.

Your healthcare provider may order a creatinine test to assess your kidney function, especially if you have any symptoms of kidney disease. Elevated serum creatinine could be a sign that your kidney function is altered. According to MedlinePlus, signs of kidney disease include:

Fatigue
Puffy eyes
Decreased appetite
Frequent and/or painful urination
Swelling of the feet and lower limbs
Foamy or bloody urine

Another important test that can be used to determine your kidney function is called a glomerular filtration rate (GFR) test. According to the University of Rochester Medical Center, your glomerular filtration rate measures the rate at which blood is filtered by your kidneys each minute.

Your GFR can be estimated using your creatinine serum levels, along with other factors such as your age, gender, and body size. If your healthcare provider orders a GFR test, you will need to get a blood sample taken and a creatinine test done.

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