Blood Urea Nitrogen (BUN)

Routine annual

also urea

What it isBUN measures the nitrogen content of urea, the molecule the liver creates to package and excrete the nitrogen waste from protein metabolism. Kidneys filter it out.

DoesReflects the intersection of protein intake, liver urea synthesis, kidney filtration, and hydration status.

GoodA mid-range BUN signals balanced protein metabolism, intact liver and kidney, and good hydration.

BadHigh BUN signals dehydration, high protein intake, kidney impairment, or gastrointestinal bleeding. Low BUN can indicate low protein intake or liver dysfunction.

Standard

7–20 mg/dL.

Optimal

10–16 mg/dL (narrow target)

Modifiers

Rises with dehydration, high protein intake, and kidney disease; falls with low protein intake and liver disease.

How to optimize

Lifestyle: Hydrate adequately; avoid chronic NSAIDs; manage blood pressure.
Diet: Adequate but not excessive protein; plenty of vegetables.
Supplements: —
Peptides: —
Drugs: ACE inhibitors, ARBs, SGLT2 inhibitors for kidney protection.

within Kidney