BUN/Creatinine Ratio: What Your Result Means

Result guide · Kidney

Content last reviewed 2026-09-12 · Educational information — not medical advice

Quick answer

The BUN/creatinine ratio compares two kidney-related waste products. It is most useful for telling dehydration and other pre-kidney causes from actual kidney damage — a high ratio usually points to dehydration or reduced blood flow, not kidney failure.

What is BUN/Creatinine Ratio?

Blood urea nitrogen (BUN) and creatinine are both cleared by the kidneys, but they behave differently: BUN is affected by hydration, protein intake, and liver function, while creatinine is produced steadily by muscle. Dividing BUN by creatinine (both in mg/dL) gives a ratio that helps sort the cause of abnormal kidney numbers.

Typical reference interval: Commonly about 10–20 (BUN and creatinine in mg/dL); the reference range varies by laboratory.. Laboratories differ — the interval printed on YOUR report always governs.

If your BUN/Creatinine Ratio is high

Common reasons BUN/Creatinine Ratio runs above the reference interval:

  • Dehydration — the most common cause — reduced blood flow concentrates both, but BUN more
  • Reduced kidney blood flow — heart failure, shock, or narrowing of the kidney arteries
  • High protein intake or GI bleeding — blood in the gut is absorbed as protein and raises BUN
  • Corticosteroids — can raise BUN
  • Urinary obstruction — can raise the ratio

If your BUN/Creatinine Ratio is low

Common reasons BUN/Creatinine Ratio runs below the reference interval:

  • Liver disease — the liver makes less urea, lowering BUN
  • Overhydration — dilution lowers BUN
  • Low protein intake or malnutrition — less urea produced
  • Pregnancy — physiologically lower BUN

Symptoms worth knowing

The ratio causes no symptoms; thirst, reduced urine output, swelling, or confusion reflect the underlying hydration or kidney problem.

What usually happens next

  1. A high ratio with normal creatinine often simply means dehydration — recheck when hydrated
  2. A rising creatinine with a normal ratio suggests kidney damage and needs prompt clinical review
  3. Read the ratio with eGFR, electrolytes, and your clinical context

Get your BUN/Creatinine Ratio checked

These lab tests measure BUN/Creatinine Ratio directly. Ordering online takes a few minutes and results arrive securely.

Order a BUN/Creatinine RatioComprehensive Metabolic Panel

We may earn a commission when you order through partner links on the following pages. Educational information here never replaces advice from a qualified healthcare provider.

Panels that include this value

BUN/Creatinine Ratio appears as one line inside these broader panels — better value than ordering single markers alone:

Basic Metabolic Panel

Related result guides

BUN (Blood Urea Nitrogen) guideCreatinine (Serum) guideeGFR (Estimated Glomerular Filtration Rate) guide

Frequently asked questions about BUN/Creatinine Ratio results

Does a high BUN/creatinine ratio mean kidney failure?

Usually not — it most often reflects dehydration or reduced blood flow. Kidney failure is better judged by creatinine and eGFR, which the panel includes.

Can the ratio be low normally?

Yes — low protein intake, pregnancy, and liver disease lower it; a low ratio with normal creatinine is often not concerning.

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