A context marker

BUN (urea): protein & hydration

Blood urea nitrogen is the waste from processing protein — the liver turns ammonia into urea (the urea cycle), the kidneys clear it. On its own it’s noisy, but in context it’s useful.

High BUN: high-protein intake, a catabolic deficit, dehydration (part of that concentration signature), or kidney strain. Low BUN: low protein intake or liver issues. Read it with hydration and creatinine.

Use BUN to confirm a story — dehydration, very high or very low protein — not as a stand-alone alarm.

The urea cycle — how protein waste becomes urea for the kidneys