Kidney
Urea Nitrogen (BUN)
What This Marker Tells Us
Measures the waste product from protein breakdown, revealing kidney filtration capacity, hydration status, and protein metabolism
Why It Matters
Reflects kidney function since kidneys filter urea from blood. Elevated BUN indicates reduced kidney filtration, dehydration concentrating the blood, or excessive protein breakdown from high-protein diets, muscle damage, or catabolic states. Low BUN suggests overhydration, liver disease impairing urea production, or inadequate protein intake. BUN helps detect kidney disease early, assess hydration, and guide protein intake recommendations.
How to Interpret Your Trends
Low BUN (below 7 mg/dL) may indicate overhydration, low protein intake, or liver dysfunction. Typical BUN (7-20 mg/dL) suggests normal kidney function, hydration, and protein metabolism. Elevated BUN (21-40 mg/dL) indicates dehydration, high protein intake, kidney stress, or increased protein breakdown. High BUN (above 40 mg/dL) signals significant kidney dysfunction, severe dehydration, or excessive catabolism requiring medical attention.
What Influences This Marker
Hydration status rapidly affects BUN; dehydration concentrates blood, elevating BUN. High-protein diets, creatine supplementation, and intense exercise increase urea production. Kidney disease impairs clearance. Low protein intake, overhydration, and liver disease lower BUN. Certain medications affect levels. Adequate hydration and balanced protein intake maintain optimal levels.
How Your Team Uses It
Your coach uses BUN to assess hydration status, guide protein intake recommendations, and monitor kidney function. Elevated BUN prompts investigation of hydration, protein intake, and kidney health. Comparing BUN to creatinine helps distinguish between hydration issues and kidney dysfunction. It informs nutrition timing around testing.
Related Signals We Also Review
Creatinine, BUN/creatinine ratio, eGFR, electrolytes, hydration markers, and protein intake complete the kidney function and hydration assessment.