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A Guide to the RFT Blood Test

written by: angiem1981•edited by: Diana Cooper•updated: 11/17/2010

The RFT blood test refers to a few commonly used tests to screen for renal function. These tests often include the BUN and the creatinine tests. In many cases, they are ordered in combination to determine the efficiency of the kidney.

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    Why Would the Test be Ordered?

    There are multiple reasons that your physician may order the RFT blood test, the primary reason being to monitor renal functioning. Those suffering from kidney disease, going through dialysis or who are believed to have kidney damage may need to have this test performed. Testing may also be required when the patient suffers from any condition that may be worsened by abnormality of the kidneys or routinely when taking certain prescription medications. In some cases, the creatinine and BUN are a part of other tests, such as a basic metabolic panel, commonly referred to as the BMP.

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    BUN and Creatinine Significance in Testing

    The BUN or blood urea nitrogen is used to measure the blood urea nitrogen. This is a waste product of the body that is excreted from the kidneys. When there is damage or disease, the levels in the blood stream can rise or decrease. Creatinine is also a waste product of the body that is excreted through the kidneys. Both are effective in determining abnormalities of this organ, which is why they compromise the majority of renal function tests.

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    How is the RFT Test Performed?

    Although the creatinine test specimen can come from urine, the BUN is strictly a blood test. When ordered together with complete RFT testing, both are typically a simple blood test. Despite the fact that there are no special testing preparations, such as fasting, caution is warranted. Various medications can alter the test results. It is always recommended to consult with your physician regarding any medications being taken, regardless if they are over the counter or by prescription for this reason. The small sample of blood needed for testing is usually aspirated via a needle from the arm and is a rather quick procedure.

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    RFT Blood Test Results

    The results of the tests may differ slightly between labs. However, normal values for the BUN are typically between 7-20 mg/dL or simply milligrams per deciliters and creatinine levels between 0.8 and 1.4 mg/dL. The patient should also keep in mind that there are discrepancies in creatinine levels between men and women. Due to increased muscle mass in comparison to females, males usually have higher levels.

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    Other Important Considerations

    There are several factors that the patient may want to consider, especially if the RFT results come back abnormal. Various disorders, diseases and even the patient’s lifestyle can cause abnormal results. For example, those with poor nutrition, those that consume too many fluids and individuals with certain other disorders may have altered RFT levels. In the event that findings are concurrent with possible kidney damage, the physician will more than likely order additional tests. You should always address your doctor with any questions or concerns about the test or the findings.

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    BUN. Lab Tests Online. Updated 22, October 2010. Viewed 15, November 2010.

    BUN. Medline Plus. Updated 13, May 2009. Viewed 15, November 2010.

    Creatinine. Lab Tests Online. Modified 22, October 2010. Viewed 15, November 2010.

    Creatinine-Blood. Medline Plus. Updated 7, August 2009.Viewed 15, November 2010.