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How Diabetes Affects the Kidneys

How Diabetic Kidney Disease Works

Spaghetti, anyone? The handy kitchen device known as a colander works by letting water pass through its tiny holes, leaving behind pasta or whatever food you're straining. But what if the holes in a colander suddenly expanded to the size of, say, the pockets on a pool table? Obviously, the noodles would slip through easily, dropping into the sink and possibly down the drain. Result: You go hungry.

The nephrons in your kidneys are kind of like colanders, allowing very small waste particles to pass through but holding back proteins and other larger molecules, ushering them back into circulation. However, elevated blood sugar fouls up this process. Glucose reacts with proteins in the body to produce demon compounds called advanced glycosylation end products, or AGEs.


Over time, if blood sugar is not well controlled, AGEs accumulate on the walls of the blood vessels in the kidneys, which makes the nephrons' filters too porous or leaky. As a result, protein molecules begin to slip through the kidneys' filters and into the urine. This phenomenon is called proteinuria, though when it's detected at an early stage doctors call it microalbuminuria (albumin is a simple form of protein).

At first, losing a little protein in the urine is no big deal. In fact, you won't even notice the problem, though as proteinuria progresses, you may observe that your urine looks a bit frothier. (If you're in the habit of observing such things.) Even though some of your nephrons are struggling, each kidney packs a million of the filtering units, so the organs are able to keep up with the body's demands for the first few years. (The body is capable of running just fine if you donate a kidney or one of yours quits working.)

Over time, however, exposure to high glucose levels -- as well as the effects of hypertension, smoking, and certain other conditions -- begins to destroy huge numbers of glomeruli, dramatically reducing the kidney's filtering capacity. Not only does the body lose protein, but more waste products remain in the blood, especially substances called creatinine and urea. About 80 percent of type 1 diabetes patients who develop persistent microalbuminuria but don't receive adequate medical care will progress to full-blown kidney failure within 10 to 15 years.

Symptoms of advanced kidney failure may include

  • high blood pressure (though hypertension causes kidney problems, too; more on that later)
  • swelling, especially around the eyes or ankles. Excess amounts of protein and salt in the urine cause water to pool in tissues. This may be accompanied by weight gain.
  • loss of appetite
  • nausea, vomiting
  • headache
  • itchiness
  • fatigue and poor sleep
  • frequent need to urinate at night
  • difficulty concentrating
  • an all-around blah feeling
  • and, of all things, frequent bouts of the hiccups, which for some reason often accompany kidney failure

To learn more about diabetes and how it can wreak havoc on your kidneys, visit the following links:

  • Diabetes sufferers can develop diabetic kidney disease, which can lead to complications such as kidney failure. Find out how you and your doctor can spot the warning signs at the main Diabetic Kidney Disease page.
  • The classic signs of diabetes are insatiable thirst and excessive urination. Visit the main Diabetes Symptoms page to learn more about the common symptoms of this dangerous ailment.
  • Diabetes is a growing health problem in the United States, now affecting approximately 20.8 million Americans. Go to the main Diabetes page to learn about type 1 and type 2 diabetes.
  • Your kidneys are responsible for regulating the composition of your blood, stimulating the production of red blood cells, maintaining your calcium levels, and regulating your blood pressure. Learn all about these essential organs in How Your Kidneys Work.

Timothy Gower is a freelance writer and the author of several books. His work has appeared in many magazines and newspapers, including Prevention, Health, Reader's Digest, Better Homes and Gardens, Men's Health, Esquire, Fortune, The New York Times, and The Los Angeles Times.


Dana Armstrong, R.D., C.D.E., received her degree in nutrition and dietetics from the University of California, Davis, and completed her dietetic internship at the University of Nebraska Medical Center in Omaha. In private practice for 21 years, she has developed educational programs that have benefited more than 5,000 patients with diabetes. She is the cofounder and program director of the Diabetes Care Center in Salinas, California..

Allen Bennett King, M.D., F.A.C.P., F.A.C.E., C.D.E., received his degrees and training at the University of California, Berkeley; Creighton University Medical School; the University of Colorado Medical Center; and Stanford University Medical Center. He is the author of more than 50 papers in medical science and speaks nationally on new advances in diabetes.

This information is solely for informational purposes. IT IS NOT INTENDED TO PROVIDE MEDICAL ADVICE. Neither the Editors of Consumer Guide (R), Publications International, Ltd., the author nor publisher take responsibility for any possible consequences from any treatment, procedure, exercise, dietary modification, action or application of medication which results from reading or following the information contained in this information. The publication of this information does not constitute the practice of medicine, and this information does not replace the advice of your physician or other health care provider. Before undertaking any course of treatment, the reader must seek the advice of their physician or other health care provider.