Which etiology results in an elevated bun level with a normal serum creatinine level?

Multiple causes: BUN is a breakdown of ingested protein, but becomes elevated compared to creatine, in cases of increased catabolism (breakdown). Such things as a high protein diet, use of some steroids, some infections, or volume depletion may commonly raise BUN levels. In a hospital setting, tube feeding, tpn, GI bleeding, infections, decreased flow to the kidneys, and use of steroids are frequent contributors.