Creatinine & BUN are normal molecules found in the blood at a concentration within a specific range. We measure these two proteins as an indicator of kidney function. Creatinine and BUN tests on blood measure the kidney’s ability to filter these molecules from the blood.
If the kidney does not filter the blood adequately, either because there is poor blood flow to the kidney (low blood pressure, dehydration) or the kidney does not function properly (kidney failure) then either of these molecules would be expected to increase to abnormally high concentrations in the blood.
Blood is collected and usually analyzed in-house, and results are available within minutes to hours.
Reasons to UseRelated Observations
BUN and Creatinine are commonly measured and helpful indicators of kidney function. BUN and Creatinine are routinely measured within a typical chemistry profile. Most hospitals provide this test. The test is quick to perform and relatively inexpensive.
BUN and Creatinine do not necessarily distinguish between poor blood flow to the kidney versus poor kidney function. In either case, the values might rise outside of normal limits. Urinalysis can be helpful in differentiating these conditions.
BUN and Creatinine are not very sensitive indicators of poor kidney function. It is said that 75% of kidney function must be lost before we expect to see rises in these indicators on a blood test.
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