BUN/ Creatinine and the Evaluation of Renal Functioning

Creatinine .7 – 1.4 – BUN 7-24 – GFR- Glomerular Filtration Rate

Here is My Renal BUN/Creatinine Evaluation of Renal Conditions

LABS BUN CR GFR Blood Urea Nitrogen Creatinine Nursing KAMP StickEnotes TWS 005


BUN stands for blood urea nitrogen. Urea nitrogen is what forms when protein breaks down. The interesting thing about BUN is that protein is initial broken down into the byproduct of Ammonia which is toxic to the body. It is then sent to the liver to be further broken into blood urea nitrogen which is able to be filtrated out of the body- That is why patients with liver disease have increased level of ammonia and need lactulose and also why low BUN is liver disease.

Also, since BUN is the byproduct of Protein breakdown renal patients are also on a low protein diet to decrease the amount of waste BUN.

BUN low and Creatinine low are generally not indicators of anything Acute

Creatinine is the byproduct of muscle breakdown and is only filtered through the kidneys that is why it is indicative it increases there is a problem inside the kidneys.

Both Blood Urea Nitrogen (BUN) and the Creatinine are important when they are high. They are specific to the kidney and there functioning.  These are Kidney Labs to be taken together in the evaluation of kidney functioning.

The Glomerular Filtration Rate-(GFR) the GFR is the actual evaluation of how the kidney is working. It is only used if both the BUN and creatinine is elevated. It is used in chronic to stage the level of CKD and acute to evaluate what phase of Acute Kidney Injury AKI or Acute Kidney Failure a Person is in and how well their kidney is functioning.

STEPS to Evaluating Kidney Labs

First Step:

First step is always looking at the BUN if it is high you then look at the Creatinine next if it is normal it is most likely dehydration caused by outside the kidney.

Second Step:

Second if you see that the BUN is high and you look at the creatinine and it is also high. Think is this an ACUTE process going or CHRONIC condition Chronic Kidney Disease (CKD).

Chronic= High BUN and High Creatinine

If both are high you then look at the Glomerular Filtration Rate-(GFR) the GFR is the actual evaluation of how the kidney is working. Once a person is identified as a CKD they begin to be staged by their GFR- Less than 15! A decision is made whether they will be on dialysis or not. The GFR in CKD never gets better and can only slow the progression through medication sugar control.

Stage  Description                                                                         (GFR)

1          Kidney damage with normal kidney function                          90 or above

2          Kidney damage with mild loss of kidney function       89 to 60

3a       Mild to moderate loss of kidney function                     59 to 44

3b       Moderate to severe loss of kidney function                 44 to 30

4          Severe loss of kidney function                                        29 to 15

5          Kidney failure                                                                      Less than 15

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