How Diabetes Affects Your Kidneys

Poorly-managed diabetes can lead to kidney disease. Here's how to reduce your risk of diabetic nephropathy.

Your kidneys act somewhat like the colander you use in the kitchen. They strain out waste and keep the useful substances in your body. When your kidneys don't work well, waste can build up in the body, causing serious health consequences.

Diabetes and chronic kidney disease (which may lead to kidney failure) are tightly linked. In fact, diabetes is the leading cause of chronic kidney disease.

Kidney basics

Healthy people have two kidneys. The kidneys filter out waste. Your kidneys also help the body regulate the production of red blood cells, regulate blood pressure and help balance fluids and minerals in the body.

Blood flows through the kidneys, passing through millions of tiny filters called glomeruli. The waste products are filtered out and substances your body needs, like protein, are reserved.

Diabetes and kidney disease

People with diabetes are at higher risk for kidney disease. Poorly-managed diabetes leads to high blood sugar. Over time, this harms blood vessels all through the body, including the small blood vessels in the glomeruli. Over time, this damages the kidneys' ability to filter properly.

At first, when damaged, the glomeruli will start to leak. Small amounts of protein will be lost through urine instead of staying in the blood. This is called microalbuminuria, which is the earliest stage of kidney disease. Treatment in this stage may be able to stop the disease from becoming worse. This is why doctors routinely check your urine as part of your diabetes checkups.

If left untreated, over many years, macroalbuminuria develops. This is when large amounts of protein are lost through the urine. A diagnosis of macroalbuminuria may mean that kidney failure (end-stage renal disease or ESRD) is likely.

Kidney failure occurs when the kidneys completely lose their filtering ability and harmful waste builds up in the blood. There are only two options to treat kidney failure: a kidney transplant or dialysis.

Dialysis is a treatment that filters out the waste products. There are two main types of dialysis:

Hemodialysis uses a machine that works like an artificial kidney.
Peritoneal dialysis uses the lining of your abdomen as a filter.

Depending on the type of dialysis, you'll either need treatment every day or a few times each week.

Other ways diabetes harms the kidneys

Nerve damage often occurs in people with diabetes. Your nerves tell your brain when your bladder is full. When nerves are damaged, there may be a delay in sending this message to your brain. A full bladder may cause urine to back up and put pressure on the kidneys, which can lead to kidney damage.

Holding urine in your bladder for too long can lead to a urinary tract infection. And high blood sugar levels make it more likely that a urinary tract infection can occur. If left untreated, the infection could spread from the bladder to the kidneys.

Many people with diabetes also have high blood pressure. High blood pressure also damages the blood vessels in a similar manner as high blood sugar. The one-two punch of high blood pressure and high blood sugar can speed up the harm to the kidneys' filtering system.

A "silent" disease

Often, kidney disease comes on without any symptoms or warning signs. Make sure to go to all your diabetes-related checkups. Your doctor will check your urine for protein and measure your blood pressure. Your doctor may also measure your eGFR — your estimated glomerular filtration rate — to find out how well your kidneys are functioning.

If you have symptoms, you may already have serious kidney damage. Symptoms can vary greatly between people. Some may include:

Fluid build-up
Loss of appetite
Nausea
Weakness

How to reduce your risks

Controlling your blood sugar and blood pressure are the most important steps in cutting your kidney disease risk. Additional measures may include:

Take all medications as directed to help lower your risk of potential complications such as heart disease, in addition to medications your doctor may prescribe to help reduce your blood sugar.
Keep your blood pressure in check.
Manage chronic medical conditions that may affect your kidneys.
Do not smoke. If you do, quit.
Get your kidney function tests done as often as your doctor recommends. Ask your doctor how often your kidneys will need to be screened and if medications to help protect your kidneys are right for you.
Eat a nutritious diet of fruits, vegetables, whole grains, lean protein and low-fat or fat-free dairy. Limit foods high in saturated fat, sodium and added sugars and avoid trans-fats. Make sure to work with your diabetes care team to determine what’s right for you, depending on your calorie and carb needs. If you already have kidney disease, your doctor may recommend that you eat only moderate or reduced amounts of protein.
Exercise is recommended for most people with diabetes. Moderate-intensity aerobic exercise should be done at least 150 minutes per week. But before you start an activity or increase your activity level, always talk to your doctor first.

Strength-train. In addition to aerobic exercise, people with type 2 diabetes are recommended to perform resistance exercises at least twice a week, provided there are no contraindications. Check with your doctor to see what exercises are safe.

By Jenilee Matz, MPH, Contributing Writer

Sources
American Diabetes Association. Standards of Medical Care in Diabetes—2015. Accessed: October 26, 2015.
American Diabetes Association. Kidney disease (nephropathy). Accessed: October 26, 2015.
United States Department of Health and Human Services: National Kidney and Urologic Diseases Information Clearinghouse. Kidney disease of diabetes. Accessed: October 26, 2015.
United States Department of Health and Human Services: National Kidney and Urologic Diseases Information Clearinghouse. The kidneys and how they work: What are the kidneys and what do they do? Accessed: October 26, 2015.

Last Updated: October 26, 2015