Blood urea nitrogen to-Creatinine Ratio
(BUN)

Sample type:

serum (red tube) or urine.

Uses:

The rationale for the use of creatinine or urea measurement to assess renal function is that plasma/serum levels of both reflect glomerular filtration rate (GFR), the parameter that defines kidney function for the clinician. Irrespective of its cause, kidney disease is associated with decrease in GFR, and the severity of kidney disease correlates closely but inversely with GFR.

Precaution:

1) Calculate creatinine and BUN correctly

2) this parameter is a ratio: BUN creatinine ratio = blood urea nitrogen (mg/dL) / serum creatinine (mg/dL).

3) may need to fast (not eat or drink) for several hours before the test. Your provider will let you know if there are any special instructions to follow.

Interfering factors:

1) Sickle cell anemia: in this condition kidneys reabsorb less urea and more of it is lost in the urine, resulting in lower BUN.

2) Hypothyroidism: a condition where the thyroid glands do not produce enough thyroid hormone. This condition can increase creatinine levels.

3) Gut bleeding: The blood in the gut gets digested and this increases the amount of protein and BUN levels.

Pre analytical error:

1) The patient is not fasting.

2) Not taking a patient history.

Corrective action:

1) Must be fasting (not eat or drink) for several hours before the test.

2) The technician must know the patient’s history.

Post analytical error:

There is a problem in delivering the results or writing them in the patient report

Corrective action:

Attention when communicating the results to the patient.

reference Range:

The normal range for BUN/Creatinine ratio is anywhere between 5 – 20 mg/dL.