Bun and creatinine. Question: Recent labwork revealed an elevated BUN of 34 w/ a ref range of 5-26. Creatinine was 0.69 w/ ref range of 0.5-1.50. BUN/creatinin ratio was elevated at 49 w/ ref range of 8 to 27. This was a fasting sample (approx 12 hours w/o food or drink)....