What Is Chronic Kidney Disease? Causes, Tests, Stages and Outlook

By Anna Curran, RN, BSN, PHN · Last reviewed October 2026

What is chronic kidney disease? Chronic kidney disease (CKD) means your kidneys are damaged or have a problem with their structure, so they cannot filter your blood as well as they should. It usually develops slowly over months or years. Most people have no symptoms early on, which is why simple blood and urine tests matter so much.

CKD is very common. The CDC estimates that about 14% of U.S. adults, roughly 37 million people, have it. About 9 in 10 adults with CKD do not know they have it. The good news is that finding it early gives you and your care team time to protect the kidney function you have.

What Your Kidneys Do

Most people have two kidneys. Each one is about the size of a fist and sits just below the rib cage, on either side of the spine. They work around the clock.

According to the National Kidney Foundation, healthy kidneys:

Filter waste and extra water out of your blood and send it out as urine
Help keep minerals like sodium, potassium and phosphorus in balance
Help control blood pressure
Help your body make red blood cells
Help keep your bones healthy

When the kidneys are damaged, waste and fluid can build up in the body. Over time, this can affect your heart, blood, bones and energy level.

What Causes Chronic Kidney Disease?

In adults, the two most common causes are diabetes and high blood pressure.

Diabetes

High blood sugar over many years can damage the tiny blood vessels inside the kidneys that do the filtering. The CDC reports that about 38% of adults with diabetes have CKD. People with prediabetes can have it too.

High blood pressure

High blood pressure puts extra force on the blood vessels in the kidneys. Over time, that wears them down. It also works the other way: damaged kidneys can raise blood pressure. This is why the two so often show up together.

Other causes

Many other conditions can lead to CKD, including:

Glomerular diseases, which damage the kidney’s filters
Inherited conditions, such as polycystic kidney disease
Autoimmune diseases, such as lupus
Kidney stones, blockages or long-lasting urinary tract infections
Some medicines, especially regular use of certain pain relievers
A past acute kidney injury (sudden kidney damage)

Sometimes the exact cause is not clear. Your provider may order more tests, such as a kidney ultrasound, to look for it.

Who Is at Risk?

You may be at higher risk if you have:

Diabetes
High blood pressure
Heart disease or heart failure
A family history of kidney disease or kidney failure
Obesity
A history of smoking

Risk also goes up with age. CDC data show CKD in about 34% of adults age 65 and older. NIDDK notes that Black or African American, Hispanic, American Indian, Native Hawaiian and Pacific Islander people are more likely to develop advanced kidney disease.

If any of these apply to you, ask your provider about kidney testing. NIDDK advises yearly testing for people with diabetes.

How Chronic Kidney Disease Is Diagnosed

Because early CKD rarely causes symptoms, testing is often the only way to find it. Two simple tests do most of the work.

eGFR (blood test)

eGFR stands for estimated glomerular filtration rate. It shows how well your kidneys filter waste. It is calculated from a blood test for creatinine, a waste product from your muscles, along with your age and sex.

60 or higher is in the normal range for most people
Below 60 may mean kidney disease
15 or lower means kidney failure

For eGFR, higher numbers are better.

Urine albumin (UACR)

The urine albumin-to-creatinine ratio, or UACR, checks for a protein called albumin in your urine. Healthy kidneys keep albumin in the blood. Damaged kidneys let some leak out.

Under 30 mg/g is normal
30 mg/g or more may be a sign of kidney damage

For UACR, lower numbers are better. A higher number also points to a higher risk of CKD getting worse and of heart disease. Because one test can be off, your provider may repeat it to confirm.

Putting it together

CKD is usually diagnosed when the eGFR stays below 60, the UACR stays above 30, or both, for 3 months or longer. One abnormal result after an illness or a hard workout does not mean you have CKD. That is why your provider looks for a pattern over time.

The 5 Stages of Chronic Kidney Disease

CKD is divided into five stages based mostly on your eGFR. Your UACR is tracked alongside it, because together they show your overall risk.

Stage	eGFR	What it means
1	90 or higher	Normal filtering, but signs of damage such as albumin in urine
2	60 to 89	Mild loss of function
3a	45 to 59	Mild to moderate loss
3b	30 to 44	Moderate to severe loss
4	15 to 29	Severe loss
5	Below 15	Kidney failure

Your stage helps guide your treatment, how often you need lab work and when to see a kidney specialist (nephrologist). For a closer look at each stage and the symptoms that may come with it, see chronic kidney disease stages and symptoms.

Why CKD Affects More Than Your Kidneys

CKD can lead to other health problems. NIDDK and the National Kidney Foundation list these common complications:

Heart disease and stroke
High blood pressure
Anemia (low red blood cells), which can make you tired
Bone and mineral problems
High potassium, which can affect your heart rhythm
A buildup of acid in the blood (metabolic acidosis)

Heart disease is one of the biggest risks for people with CKD. Many of the steps that protect your kidneys also protect your heart.

What Is the Outlook?

There is no cure for CKD, and advanced kidney damage usually cannot be reversed. But CKD does not always get worse quickly. Many people stay in an early or middle stage for years.

How fast it changes depends on the cause and how well things like blood pressure and blood sugar are controlled. The American Kidney Fund notes that with treatment and healthy changes, many people in stage 3 do not move on to stage 4 or 5.

Today there are more tools than ever to slow CKD. These include blood pressure control, blood sugar control and several medicines shown to protect the kidneys. You can read more in how to slow chronic kidney disease. Food choices matter too, and a chronic kidney disease diet is set based on your stage and your labs.

If kidneys do fail, treatment options include dialysis, a kidney transplant or conservative care focused on comfort and symptom control. Your care team will talk about these well ahead of time.

Frequently Asked Questions

Can chronic kidney disease be reversed?

Advanced, long-lasting kidney damage usually cannot be reversed. But early diagnosis and good care can often slow it down and help you keep the function you have. Some causes of kidney damage can be treated, which is why finding the cause matters.

Does CKD always lead to dialysis?

No. Many people with CKD never reach kidney failure. Keeping blood pressure and blood sugar in your target range, and taking kidney-protecting medicines your provider prescribes, can lower that risk.

Can I have kidney disease and feel fine?

Yes. Most people with early CKD feel completely normal. That is why blood and urine tests are so important if you have diabetes, high blood pressure, heart disease or a family history of kidney failure.

What kind of doctor treats CKD?

Your primary care provider often manages early CKD. As it advances, or if your numbers change quickly, you may be referred to a nephrologist, a doctor who specializes in kidneys. A kidney dietitian can also help with food choices.

The Bottom Line

Chronic kidney disease means your kidneys are damaged and not filtering blood as well as they should. Diabetes and high blood pressure cause most cases, and early CKD usually has no symptoms. Two simple tests, eGFR and urine albumin, can find it early. Ask your provider about testing if you are at risk, and know your numbers so you can work with your care team to protect your kidneys.