BUN/Creatinine ratio

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Latest Edit: Iva Lloyd, ND 2021-08-24 (EDT)

See Also Lab Tests

BUN/Creatinine is dependent on the BUN and Creatinine levels. This ratio is used to assess patients with chronic renal dysfunction and serves as a rough guide, due to the variability in BUN and Creatinine levels.[1], [2]


  • An increased ratio is caused by either a decreased creatinine or an increased BUN level.
  • A decreased ratio is caused by either a decrease in BUN with an increase in creatinine or a normal BUN with a greatly increased creatinine.

Patient Preparation

No preparation is required

Clinical Implications

Ranges: The following are the reference ranges for this lab. However, lab ranges can vary by laboratory and country. [2]

Standard U.S. Units Standard International Units
Conventional Laboratory Range 6-20 7-14
Optimal Range 10-16 13-17
Alarm Ranges < 5 or > 30 < 4 or > 31

High levels indicate:

Low levels indicate:

  • Low protein diet
  • Posterior pituitary dysfunction
  • Drug causes: Cephalosporin (antibiotics), Phenacemide (anti-convulsant)
  • Other conditions: pregnancy (normal), liver dysfunction, Diabetic acidosis, Dialysis

Associated Tests


  1. Pagana Kathleen D, Pagana Timothy J (1998) Mosby's Manual of Diagnostic and Laboratory Tests, Mosby, Inc
  2. 2.0 2.1 Weatherby Dicken, Ferguson Scott (2002) Blood Chemistry and CBC Analysis: Clinical Laboratory Testing from a Functional Perspective, Bear Mountain