What is Creatinine Clearance

What is Creatinine Clearance?

June 25, 2019

Your urine is an indicator of your health. Accordingly, there are several methods that help determine certain issues by testing the components of this liquid excrement. This article will specifically discuss creatinine clearance, a laboratory test for detecting and diagnosing kidney problems.



The human urine is mainly composed of water, as well as other compounds including urea, chloride, sodium, potassium, creatinine and other water-soluble nitrogen materials and dissolved ions. This liquid by-product is released by the kidneys after filtering blood, which typically sums up the process of urination.

Determining Disease Through Urine

Urine is a sterile and non-toxic solution which contains molecules from carbon dioxide and toxic ammonia. Any materials present in the urine which is not included in the main components of its chemical composition can be indicators of health problems. For instance, hematuria is a condition determined by the presence of red blood cells in the urine. Another abnormal condition is proteinuria, which is characterized by the presence of protein compounds which can potentially damage the tubules due to their impassable size.

Injuries and infections can also be determining factors of illnesses. For example, oliguria is a condition caused by kidney damage, associated with the symptom of releasing abnormally little urine. Polyuria, on the other hand, is triggered by diabetes and has the exact opposite symptom—the release of too much urine. Another condition, dysuria, is characterized by painful urination that is caused by urinary tract infections.

Urine Substance Levels

According to the Health Encyclopedia of the University of Rochester Medical Center, there are normal ranges for the substances found in urine. To determine if they are at the right levels, certain tests can be taken. These tests are able to detect urine characteristics such as cells, properties, and specific pH. An example is a urinalysis, which can be performed on test samples using light microscopy. More tedious tests are urinary casts, which can detect details such as the numbers and types of materials for the diagnosis of more advanced diseases.


Creatinine Clearance

Creatinine clearance is a test for measuring the level of the substance creatinine. Results are often provided in grams per day (g/day). The normal range of your creatinine is dependent on factors like your age, gender, and muscle mass. For adult men, the amount must be 0.8 to 1.8 g/day, and for adult women, the range is 0.6 to 1.6 g/day. Higher creatinine levels may indicate kidney disease.

Creatinine is a substance created by the muscles as a result of breaking down the compound creatine. It is then filtered from the kidneys and secreted into the urine. An article reviewed by Dr. Chad Haldeman-Englert, a clinical geneticist, reports that creatinine amount is relatively sustained for each person. The amount of creatinine extracted from the blood is dependent on both the rate at which blood is transported to the kidneys and the kidneys’ ability to filter blood.

Creatinine clearance is also a method of calculating the glomerular filtration rate (GFR) which is the amount of blood filtered by the kidneys within a minute. A decrease in the GFR can be an indicator of kidney damage as it can slow blood circulation, which in turn, will also lower the amount of creatinine removed from the blood and passed to the urine.

According to the American Association of Clinical Chemistry, there is limited means to directly measure the GFR, thus, it is helpful to make an estimate of the GFR by measuring the blood’s creatinine level and using its results in an equation to calculate GFR.


The Procedure

In a creatinine clearance test, both the creatinine levels in a urine sample from a 24-hour collection and a blood sample are measured. The determined levels are then used for calculating the amount of creatinine extracted from the blood and released into the urine. This said calculation enables a general analysis of the amount of blood being filtered by the kidneys within a day.

A creatinine clearance requires a blood sample and a urine sample. The urine sample can either be for a “spot” or a 24-hour test. If your healthcare provider requires a “spot” urine test, you’ll be asked to collect a sample, preferably from your first urination in the morning. As for the 24-hour urine sample, you’ll be instructed to collect all the urine you release in a period of 24 hours. As for the blood sample, it will usually be drawn from the arm. Your height and weight will also be taken into account for this test.

No specific preparation is needed for this test. However, you have to inform your physician about all the medications you are currently taking including food supplements, herbal medicine, and vitamins because certain drugs may affect results. You may also be asked not to eat meat prior to the test, as consumption of cooked meat can lead to a temporary increase in creatinine level.

It’s also important to note that if you are muscular, the amount of your creatinine can be naturally higher than the normal range. Being of small stature can also cause your creatinine level to be lower than normal. Some sources also report that ethnicity can influence the level of urine creatinine.


When Should You Have this Test?

Your physician may require you to have this test if you are suspected of having kidney problems. Symptoms associated with kidney disease include fatigue or frequent exhaustion, puffy eyes, swelling in the ankles or feet, loss of appetite, skin dryness and itchiness, muscular pain, foamy or cloudy urine, difficult urination, frequent urination, and insomnia.

You may also be asked to undergo this test if you have been diagnosed with chronic kidney disease as your physician will need to regularly check your renal function to track progress and make necessary adjustments in your treatment. To date, this test poses no known health risks.


The Takeaway

Your health isn’t affected only by the food that goes inside your body but also by the substances that go out. Waste products are excreted from the body to prevent poisoning from toxic materials. These waste materials are also residues or by-products which result after a process of extracting the necessary nutrients from the food you consume and converting them into energy or fat stores for future use.

So while it is highly important to prioritize your nutrition, it’s also significant to monitor your body’s excretion of waste materials through bowel movements and urination.