BUN (Blood Urea Nitrogen): What Your Result Means
Result guide · Kidney
Content last reviewed 2026-09-12 · Educational information — not medical advice
Quick answer
BUN rises with kidney impairment but ALSO with dehydration and protein loads — making it less kidney-specific than creatinine. The BUN:creatinine ratio teases apart these causes.
What is BUN (Blood Urea Nitrogen)?
Liver converts ammonia (protein metabolism's end product) into urea; kidneys excrete most but recycle some depending on hydration state. That partial reabsorption explains BUN's volatility: concentrated kidneys reclaim urea, inflating values during dryness without any organ failure.
Typical reference interval: Commonly 7–20 mg/dL in adults; higher ranges accepted in elderly.. Laboratories differ — the interval printed on YOUR report always governs.
If your BUN (Blood Urea Nitrogen) is high
Common reasons BUN (Blood Urea Nitrogen) runs above the reference interval:
- Dehydration — the great mimicker — ratio climbs above 20:1 with creatinine stable
- High protein intake, GI bleeding — blood in the gut is literally a protein meal
- Kidney impairment — alongside creatinine, proportionately
- Heart failure — poor renal perfusion concentrates urea
- Catabolic states — burns, sepsis, steroids breaking down tissue
If your BUN (Blood Urea Nitrogen) is low
Common reasons BUN (Blood Urea Nitrogen) runs below the reference interval:
- Liver failure — hepatic urea-cycle failure starves production — BUN plummets in end-stage liver disease
- Malnutrition/low protein — little substrate
- Pregnancy — expanded filtration
- SIADH — dilution
Symptoms worth knowing
Urea itself contributes to uremic symptoms only at extreme kidney failure: nausea, confusion, pericarditis. Most elevated-BUN encounters reflect dryness causing dizziness and dark urine rather than uremia.
What usually happens next
Get your BUN (Blood Urea Nitrogen) checked
These lab tests measure BUN (Blood Urea Nitrogen) directly. Ordering online takes a few minutes and results arrive securely.
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 (Blood Urea Nitrogen) appears as one line inside these broader panels — better value than ordering single markers alone:
Related result guides
Frequently asked questions about BUN (Blood Urea Nitrogen) results
Is high-protein diet raising my BUN?
Very likely, yes — carnivore/keto adherents routinely run 25+. Harmless in healthy kidneys, but worth documenting so future readers of your chart don't chase phantom renal decline.
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