BUN and Creatinine Tests Help Spot and Track Kidney Problems

Q:  My doctor checks my blood 3 or 4 times a year. My BUN averages 26 and my creatinine averages 1.9.

I understand these numbers indicate kidney problems, but since they are steady, my doctor doesn't seem concerned, and only suggests I drink more water.

I am worried, since this has been a problem for several years. Will I be on dialysis in the future? Do I only need to drink more water?

A:  Both BUN (Blood Urea Nitrogen) and creatinine are by-products of digested foods that are not needed for the body's essential functions and therefore are excreted in the urine. A normal kidney easily removes creatinine and so, when creatinine is high (over 1.1), it means that the kidney isn't working 100%, which is most probably your case.

BUN and creatinine are tested by taking a sample of blood from a vein in the arm; sometimes your doctor might also request a urine sample for creatinine.

Drinking water will help the kidney flush out unwanted metabolites only when you are dehydrated. If you are drinking fluids as a usual practice and if your creatinine is stable throughout the years, I doubt dehydration is your problem. (Additionally, dehydrated patients have a much higher BUN.)

The most common cause of chronically poorly functioning kidneys is disease from high blood pressure or diabetes, but there are other causes like a large prostate obstructing urine flow and hardening of the arteries to the kidneys. You should ask your doctor what the origin of your kidney problems are.

The progression of kidney disease to a severity requiring dialysis depends on many factors, primarily your overall health and the origin of the kidney disease.

The fact that you have not had deterioration of function over the past few years is a good sign, and maybe your doctor is already taking the necessary steps to prevent further worsening. If not, it's not too early to consult a kidney doctor specialist. They like to see patients when the creatinine gets above 1.5-2.0.

Julie L. Mitchell, MD, MS, is an Assistant Professor of Medicine at the Medical College of Wisconsin. She practices at the Froedtert & The Medical College of Wisconsin General Internal Medicine Clinic - East. Her column appears in the Milwaukee Journal-Sentinel.