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Like most people, you may not often think about your kidneys. If you have diabetes, though, it's a good idea to start giving them more thought. 

Though diabetes is the leading cause of kidney failure, you won't have symptoms from early kidney disease. But simple tests can check how your kidneys are working and detect early disease linked to diabetes. Treating kidney disease early can make a huge difference. Drugs, changes in your diet, and good control of your blood sugar (glucose) levels and blood pressure can slow down or prevent kidney damage.

The key is to get diagnosed early and start treatment right away, says Robert Stanton, MD, chief of nephrology at the Joslin Diabetes Center Clinic. If you have diabetes, here's what you need to know.

How Diabetes Damages Kidneys

Your kidneys filter your blood. They get rid of wastes in your body through urine, while the cleaned blood is sent back into your body.

Chronic high blood sugars make your kidneys work harder to filter blood and can damage them, so they don't filter it as well. Small amounts of protein start to leak into your urine -- a first sign of the damage. The damage may worsen and blood pressure may start to rise. This puts more stress on your kidneys, causing more protein to leak into your urine. Your kidneys don't work well and waste products start to build up in your blood.  

High blood glucose levels may not be the only diabetes-linked cause of damage to kidney cells. "Kidney damage in type 1 diabetes is largely the result of high glucose," says Janet B. McGill, MD. She's an endocrinologist and professor of medicine at the Washington University School of Medicine in St. Louis. "But in type 2, it could have many causes. There may be an interaction between high blood glucose, high blood pressure, inflammation, age, and genetics."

If you don't treat kidney disease, the damage can get worse until your kidneys fail to work at all. At this point -- called end-stage renal disease -- you'll need to have your blood filtered through a machine or have a kidney transplant.

How to Find Out if You Have Kidney Damage

Since you won't likely have symptoms of kidney damage early on, the only way to know if you have it is to get blood and urine tests in your doctor's office. Normal glucose testing won't tell you how well your kidneys are working. Routine urine tests may not either, says Rita Kalyani, MD, assistant professor of medicine at Johns Hopkins University in Baltimore.

If you are at risk for kidney damage, you should have these three tests, experts say.

  • Blood pressure monitoring. High blood pressure can be a sign of kidney problems and a cause of kidney damage. If you have diabetes, you need to have good control of your blood pressure. A reading below 130/80 is usually a good target, Stanton says. Talk with your doctor about the best target for you.
  • Urine tests for protein, creatinine, and albumin. Tiny amounts of protein begin to leak into your urine when kidney damage begins. Your doctor can do a test to check for protein in your urine. In the past, you might have had to collect your urine for 24 hours for this, Stanton says, but now it just takes one sample.
  • Estimating Glomerular filtration rate (eGFR or GFR). This test helps show how well your kidneys filter your blood. "I think every patient should know his GFR," Stanton says.

If you're not sure whether you've had these tests, ask your doctor.