text: Some of the causes of a high BUN level:\n\nA high BUN value can indicate kidney injury or disease. Damage can be caused by a variety of conditions, such as diabetes or high blood pressure, that directly affect the kidneys. In addition to direct damage to the kidneys, high BUN levels can be caused by blockage of the urinary tract (by an object such as a kidney stone or tumor) or reduced blood flow to the kidneys caused by dehydration or heart failure. \n\nA high BUN can be caused by medications, such as allopurinol (Alloprin), aminoglycosides (Garamycin), furosemide (Lasix), indomethacin (Indocin), methotrexate (MTX), aspirin, amphotericin B, carbamazepine (Tegretol), vancomycin (Vancocin), propranolol (Inderal), rifampin (Rifadin), spironolactone (Aldactone), tetracyclines, thiazide diuretics, and triamterene (Dyrenium). \n\nA high BUN value may also be caused by a high-protein diet, Addison's disease, tissue damage (such as from severe burns), or from bleeding in the gastrointestinal tract. \n\nA rise in BUN can indicate kidney problems caused by diabetes. \n\nHigh BUN-to-creatinine ratios occur with sudden (acute) kidney failure, which may be caused by conditions such as shock or severe dehydration. An obstruction in the urinary tract (such as from a kidney stone) can cause an elevated BUN-to-creatinine ratio. A very high BUN-to-creatinine ratio may be caused by bleeding in the digestive tract or respiratory tract.