Blood Urea Nitrogen
Blood urea nitrogen (BUN) measures the amount of nitrogen in your blood that comes from urea, a waste product made when your body breaks down protein. Your kidneys normally filter urea out.
BUN gives a window into how well your kidneys are clearing waste, and it's also affected by hydration, diet, and liver function. It's usually read alongside creatinine for a fuller picture of kidney health.
A higher BUN can reflect reduced kidney filtering, dehydration, a high-protein diet, bleeding in the digestive tract, or certain medications. Because so many factors influence it, your clinician will interpret it together with creatinine and your overall situation rather than on its own.
A lower BUN can occur with a low-protein diet, overhydration, or liver conditions. On its own, a low value is often not a cause for concern.
Typical ranges fall roughly around 7 to 20 mg/dL, though labs vary. Your clinician can tell you what your result means for you.
Sources
Educational context only, not medical advice or a diagnosis. Reference ranges vary by lab, age and sex; always discuss your results with a clinician.