Kidney disease means your kidneys are not filtering waste from your blood the way they should

Your kidneys clean your blood by removing waste and extra water, which become urine. When kidney disease develops, this filtering slows down or stops working. Waste builds up in your body instead of leaving through urine. Kidney disease can develop slowly over years, or it can appear suddenly. Some people have no symptoms until the disease is advanced, while others notice swelling, fatigue, or changes in urination early on.

Kidney disease is measured in stages, from Stage 1 (mild damage, kidneys still work well) to Stage 5 (kidney failure, kidneys work at less than 15 percent capacity). A blood test called a glomerular filtration rate, or GFR, tells you which stage you are in. Your doctor uses this number to track how much kidney function you have left and what treatment you may need.

Key Takeaways

  • Kidney disease develops when your kidneys cannot filter waste from your blood properly, and it is measured in five stages based on how much function remains.
  • High blood pressure and diabetes are the two most common causes of kidney disease, though infections, autoimmune diseases, and kidney stones can also damage kidneys.
  • Many people have no symptoms in early stages, so a blood test (GFR) or urine test is often the only way to know you have kidney disease.
  • Treatment depends on the stage and cause, and may include managing blood pressure, controlling blood sugar, changing diet, or eventually dialysis or transplant in Stage 5.
  • Slowing kidney disease progression is possible with early detection and treatment, which is why regular checkups matter if you have risk factors like diabetes or high blood pressure.

What causes kidney disease

Diabetes and high blood pressure cause the majority of kidney disease cases. High blood sugar damages the tiny blood vessels inside your kidneys over time. High blood pressure puts extra strain on those same vessels. Together, they account for roughly two-thirds of all kidney disease in the United States.

Other causes include chronic glomerulonephritis (long-term inflammation of the kidney's filtering units), polycystic kidney disease (an inherited condition where cysts grow in the kidneys), repeated kidney infections, kidney stones that block urine flow, and autoimmune diseases like lupus. Some medications, including certain pain relievers and antibiotics, can damage kidneys if used for long periods. Obesity and smoking also increase your risk.

How kidney disease is detected

You usually find out you have kidney disease through blood and urine tests, not through symptoms. A blood test measures creatinine, a waste product your kidneys filter out. Your doctor uses creatinine levels to calculate your GFR, which shows what percentage of kidney function you have. A GFR of 90 or higher is normal; below 60 for three months or longer signals kidney disease.

A urine test looks for protein or blood in your urine, which should not be there. Protein in urine is often the first sign of kidney damage. If you have diabetes or high blood pressure, your doctor may order these tests regularly even if you feel fine. If you have a family history of kidney disease, kidney failure, or diabetes, mention this to your doctor so they can monitor you.

Stages of kidney disease and what they mean

Stage 1 means your kidneys are damaged but still working at 90 percent or more. You may have protein in your urine or other signs of damage, but you likely feel normal. Stage 2 means mild loss of kidney function (60 to 89 percent working). Most people have no symptoms and do not know they have it.

Stage 3 is divided into 3a (45 to 59 percent function) and 3b (30 to 44 percent function). At this point, you may start to notice fatigue, swelling in your hands or feet, or changes in how often you urinate. Stage 4 means moderate to severe loss of function (15 to 29 percent). Symptoms become more noticeable, and your doctor will begin preparing you for Stage 5 or treatment options. Stage 5 is kidney failure (less than 15 percent function). Your kidneys cannot do the job alone, and you will need dialysis or a transplant to survive.

Managing kidney disease in early stages

If you are in Stage 1, 2, or 3, the goal is to slow the disease and prevent it from getting worse. Control your blood pressure, usually with medication. Keep your blood sugar in target range if you have diabetes. Reduce salt in your diet, as salt raises blood pressure and makes kidneys work harder. Limit protein intake slightly, since damaged kidneys struggle to clear protein waste.

Your doctor may prescribe ACE inhibitors or ARBs (angiotensin receptor blockers), medications that protect kidney function and lower blood pressure at the same time. Avoid over-the-counter pain relievers like ibuprofen and naproxen if possible, as they can harm kidneys. Stay at a healthy weight, exercise regularly, and do not smoke. See your doctor for blood and urine tests at least once a year, or more often if your GFR is dropping.

What happens as kidney disease advances

As your GFR falls below 30, your kidneys cannot keep up with waste removal. Waste builds up in your blood, a condition called uremia. You may feel sick to your stomach, lose your appetite, or feel bone pain. Your blood may become too acidic. You may develop anemia because damaged kidneys do not make enough erythropoietin, a hormone that tells your body to make red blood cells.

Your doctor will refer you to a nephrologist (kidney specialist) if you are not already seeing one. You will learn about dialysis and transplant options before you reach Stage 5. Dialysis is a machine that does the filtering your kidneys cannot do. It takes several hours, three times a week, or you can do it nightly at home. A kidney transplant means receiving a kidney from a donor (living or deceased) and taking medications to prevent rejection.

Diet and lifestyle changes that help

Eating the right foods slows kidney disease progression. Limit sodium to less than 2,300 milligrams per day (about one teaspoon of salt). Choose fresh foods over packaged ones, which are high in salt. Reduce potassium if your doctor tells you to, since damaged kidneys cannot clear potassium well. High potassium can cause heart problems. Foods high in potassium include bananas, oranges, potatoes, and tomatoes.

Limit phosphorus, another mineral damaged kidneys cannot clear. Phosphorus is in dairy, nuts, seeds, and processed meats. Eat moderate amounts of protein—your doctor or a kidney dietitian can tell you how much is right for you. Drink water as directed by your doctor; some people need to limit fluids as kidney function declines. Avoid alcohol or drink only in moderation. Work with a renal dietitian if possible; they specialize in kidney disease nutrition.

Frequently Asked Questions

Can kidney disease be reversed?

Early-stage kidney disease cannot be reversed, but its progression can be slowed significantly with treatment. Once kidney tissue is scarred, it does not heal. However, controlling blood pressure and blood sugar, taking prescribed medications, and making diet changes can keep your kidneys working longer and delay or prevent the need for dialysis.

What is the difference between acute and chronic kidney disease?

Acute kidney injury happens suddenly, often from infection, dehydration, or medication reaction, and kidneys may recover fully with treatment. Chronic kidney disease develops slowly over months or years and is permanent, though it can be managed to slow its progress. Chronic kidney disease is what most people mean when they say "kidney disease."

Do I need to see a specialist if I have early kidney disease?

Not always in Stage 1 or 2. Your regular doctor can manage early disease with blood pressure control and monitoring. You should see a nephrologist (kidney specialist) if you reach Stage 3, if your GFR is dropping quickly, if you have diabetes and kidney disease together, or if your doctor recommends it.

What should I tell my doctor about medications I take?

Tell your doctor about all medications, supplements, and over-the-counter drugs you use. Some pain relievers, antibiotics, and blood pressure medications can harm kidneys or need dose adjustment when kidney function is low. Your doctor may need to switch you to safer options or change how much you take.

How often should I get tested if I have risk factors for kidney disease?

If you have diabetes or high blood pressure, ask your doctor how often you need blood and urine tests. Many doctors recommend at least once a year. If you already have kidney disease or your GFR is dropping, you may need tests every three to six months so your doctor can catch changes early.