Another critical reason to prevent and control diabetes: It is a top cause of chronic kidney disease

JACKSONVILLE, Florida — Diabetes affects how the body uses glucose, also known as blood sugar. It can mean that there is too much sugar in the blood. This can harm people in several ways. One serious complication is chronic kidney disease. Ivan Porter II, M.D., a nephrologist at Mayo Clinic in Florida, explains the connection between diabetes and chronic kidney disease.

Up to 40% of people with diabetes develop chronic kidney disease, also called chronic kidney failure, global statistics show. Their kidneys cannot effectively do their most important job, which is regulating the composition of the blood by filtering out waste and maintaining the balance and amount of salt and water in the body.

Chronic kidney disease may be advanced before symptoms appear and a person is diagnosed. It can progress to end-stage kidney failure, which can be fatal without dialysis or a kidney transplant.

Both type 1 and type 2 diabetes can lead to chronic kidney disease. Type 2 diabetes is a far more common cause. With either type, the body can't produce enough insulin. Insulin is a hormone produced in the pancreas that helps the body convert sugar into energy. Because one of the kidneys' most important jobs is cleaning the blood, they help regulate blood glucose levels, Dr. Porter explains.

"The high levels of circulating glucose in the blood are poisonous to nerves and blood vessels, and the kidneys are a big ball of blood vessels," Dr. Porter says. "The presence of high glucose leads to chemical changes that cause protein in urine, and the presence of protein in urine directly activates factors that cause scarring and fibrosis within the kidney, leading to worsening of kidney disease."

How diabetes and chronic kidney disease overlap and interact with each other is complex. Too much glucose in the blood can damage the kidneys and lead to chronic kidney disease. At the same time, declining kidney function related to chronic kidney disease can lead to insulin resistance, which can cause type 2 diabetes. In addition, declining kidney function can worsen preexisting diabetes.

The longer you have diabetes — and the less controlled your blood sugar — the higher the risk of complications such as chronic kidney disease. 

There are five stages of kidney disease, based on the glomerular filtration rate (GFR). The GFR measures how well the kidneys filter waste from the blood. The stages are:

• Stage 1. At this stage, the GFR is 90 or higher, which is considered a healthy level. However, there is also another indicator of kidney disease present, such as blood or protein in the urine.

• Stage 2. At this stage, the GFR is 60 to 89.

• Stage 3. This stage is broken down into two subtypes — stage 3a and stage 3b. With 3a, the GFR is 45 to 59, and there is mild to moderate decline in kidney function. With 3b, the GFR is 30 to 44, and there is a more severe decline in kidney function.

• Stage 4. The GFR is 15 to 29, and kidney decline is severe.

• Stage 5. This stage is considered end-stage renal disease, also called kidney failure. The GFR is under 15. At this point, dialysis or a kidney transplant is needed.

Most often, chronic kidney disease is diagnosed in stage 3 or later.

"The presence of other comorbidities, such as uncontrolled blood pressure, uncontrolled diabetes or the presence of protein in the urine, can make what might seem like an earlier stage worse for someone," Dr. Porter says.

Not everyone living with diabetes will develop chronic kidney disease. Dr. Porter says it is critical to manage your diabetes, monitor your kidney function regularly and take steps to protect your kidney health to help lower risk.

Controlling diabetes includes managing medication, developing a healthy eating routine, exercising and planning for factors that can affect blood sugar levels, such as illness, stress, and changes in hormone levels due to menstrual cycles, perimenopause and menopause.

Type 2 diabetes has risk factors that people can try to avoid. These include preventing or treating overweight or obesity; being active; maintaining healthy levels of HDL cholesterol, also known as good cholesterol; and avoiding alcohol or limiting consumption to a moderate level. 

For more information, visit Mayo Clinic and Mayo Clinic Press.

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• Sharon Theimer, Mayo Clinic Communications, newsbureau@mayo.edu