Renal failure, also known as kidney failure, occurs when your kidneys lose their ability to clean your blood and maintain your body’s chemical balance. This serious condition affects over 750,000 people in the United States each year and requires prompt medical attention and ongoing treatment to maintain quality of life.

Understanding Kidney Function and Failure

Your kidneys are bean-shaped organs about the size of your fist, located under your ribcage toward your back. Most people have two working kidneys, though you can live well with only one functioning kidney. These remarkable organs work around the clock to filter your blood, removing waste products and extra water that leave your body as urine. Beyond this cleaning function, your kidneys also balance important minerals and salts in your blood, such as calcium, phosphorus, sodium, and potassium. They produce hormones that help control blood pressure, make red blood cells, and keep your bones strong.^[1]

When your kidneys fail, they can no longer perform these vital jobs effectively. Waste products and fluid begin to build up in your body, causing you to feel unwell. Without treatment, this buildup can become life-threatening. Kidney failure is sometimes temporary and develops quickly—this is called acute kidney failure or acute kidney injury. Other times, it’s a long-term condition that slowly worsens over time, known as chronic kidney failure.^[1]

Chronic kidney failure can progress to the most severe stage, called end-stage kidney disease (ESKD) or end-stage renal disease. At this point, your kidneys are functioning at less than 15 percent of their normal capacity. Without treatment through dialysis or a kidney transplant, end-stage kidney disease is deadly, and a person may survive only a few days or weeks. However, with proper treatment, many people can maintain a good quality of life while managing kidney failure.^[1]

How Common Is Kidney Failure

Kidney failure is a significant health concern that affects communities worldwide. In the United States alone, kidney failure affects over 750,000 people each year. Globally, approximately 2 million people live with this condition. The disease is more common than many people realize and can affect anyone, though certain populations face higher risk.^[1]

Chronic kidney disease is particularly common among older adults, though it’s important to understand that it’s not simply a normal part of aging. The condition is also more prevalent in people who are Black or of South Asian origin. Most people with chronic kidney disease are able to live long lives with the condition. Only about 2 in 100 people with chronic kidney disease will progress to kidney failure, though this risk increases if the condition isn’t properly managed.^[9]

The Five Stages of Kidney Disease

Healthcare providers classify kidney disease into five stages based on how well your kidneys filter waste from your blood. This measurement is called the estimated glomerular filtration rate (eGFR), determined through a blood test. A normal eGFR is above 90, while the lowest possible eGFR is 0, meaning no remaining kidney function.^[1]

In Stage 1, your eGFR is higher than 90. At this early stage, your kidneys have mild damage but still function normally, and you may not notice any symptoms. Stage 2 shows an eGFR between 60 and 89, indicating more damage than Stage 1, though your kidneys still work well. Stage 3 is divided into two parts: Stage 3a (eGFR between 45 and 59) and Stage 3b (eGFR between 30 and 44), representing mild to moderate or moderate to severe loss of kidney function. This is the most common stage where symptoms may begin to appear.^[1]

Stage 4 represents severe loss of kidney function, with an eGFR between 15 and 29. Your kidneys are severely damaged and close to failing. Stage 5, with an eGFR below 15, means your kidneys are nearing or at complete failure. This is generally when symptoms become noticeable and treatment with dialysis or transplant becomes necessary to sustain life.^[1]

Main Causes of Kidney Failure

The two most common causes of chronic kidney disease and kidney failure are diabetes and high blood pressure. When diabetes is not properly managed, high blood sugar levels can damage the tiny filters in your kidneys over time. Similarly, high blood pressure puts ongoing strain on the small blood vessels in your kidneys, eventually preventing them from working properly. Both conditions, when left uncontrolled, can gradually destroy kidney function.^[1]

Other important causes include various kidney-specific diseases. Glomerulonephritis, an inflammation of the kidney’s filtering units, can damage these structures. Polycystic kidney disease is an inherited condition where fluid-filled cysts develop in the kidneys. Kidney infections that occur repeatedly can cause lasting damage. Blockages in the flow of urine—from kidney stones that keep coming back or an enlarged prostate—can harm the kidneys over time.^[9]

Certain medications taken regularly over long periods can also damage kidneys. These include lithium and nonsteroidal anti-inflammatory drugs (NSAIDs) such as ibuprofen. Additionally, high cholesterol can cause fatty deposits to build up in the blood vessels supplying your kidneys, making it harder for them to work properly.^[9]

Acute kidney failure has different causes. It can result from sudden events like low blood pressure, blockage of the urinary tract, muscle breakdown, or a condition called hemolytic uremic syndrome where red blood cells are destroyed. Acute kidney injury develops rapidly—over hours or days—and can range from mild to severe enough to cause kidney failure. Many people recover kidney function over time, though this may take days, weeks, or months. For some, acute kidney injury causes permanent damage that leads to chronic kidney disease.^[4]

Risk Factors for Developing Kidney Failure

Certain groups of people face higher risk of developing kidney disease that could progress to failure. If you have diabetes, you’re at significantly increased risk—approximately 1 in 3 adults with diabetes may develop chronic kidney disease. Similarly, about 1 in 5 adults with high blood pressure face this risk. These two conditions are so closely linked to kidney disease that managing them effectively is crucial for kidney health.^[23]

Having heart disease puts you at greater risk for kidney problems, just as kidney disease increases your risk for heart problems. This connection exists because the same factors that damage blood vessels in the heart can also damage blood vessels in the kidneys. A family history of kidney failure is another important risk factor, as some kidney diseases have genetic components that run in families.^[9]

Obesity increases your risk because excess weight puts additional strain on your kidneys and increases the likelihood of developing diabetes and high blood pressure. Age is also a factor, as kidney disease becomes more common as people get older, though it’s not an inevitable part of aging. People who are Black or of South Asian origin face higher risk for reasons that aren’t fully understood but likely involve a combination of genetic, social, and environmental factors.^[9]

Recognizing the Symptoms

Many people experience few or no symptoms in the early stages of kidney disease. Chronic kidney disease may continue causing damage even when you feel perfectly fine, which is why the condition is sometimes discovered only during routine blood or urine tests done for other reasons. However, as kidney function declines, symptoms eventually appear.^[1]

If your kidneys aren’t working properly, you may notice extreme tiredness or fatigue that doesn’t improve with rest. Nausea and vomiting can occur as waste products build up in your blood. You might experience confusion or trouble concentrating, sometimes described as “brain fog.” Swelling, medically called edema, often appears around your hands, ankles, or face as your kidneys fail to remove excess fluid from your body.^[1]

Changes in urination patterns are common symptoms. You might urinate more or less frequently than usual, or wake up at night to use the bathroom. Your urine might contain blood or appear foamy. Some people develop muscle cramps or spasms. Your skin may become dry or itchy. Loss of appetite is common, and food may taste metallic or simply unappealing. You might experience shortness of breath if fluid builds up in your lungs.^[4]

In acute kidney failure, the first symptom is often a decreased amount of urine. Early symptoms may include swelling, weight gain, and changes in blood test results. Late symptoms can include worsening tiredness, confusion, changes in breathing, and seizures. Once recovery begins, you may notice an increase in urine production before returning to normal levels.^[4]

How Kidney Failure Changes Your Body

When your kidneys fail, the effects ripple throughout your entire body because these organs play such crucial roles in maintaining your health. Healthy kidneys prevent the buildup of wastes and extra fluid in your body while balancing salts and minerals in your blood. They also produce hormones that control blood pressure, stimulate red blood cell production, and maintain bone strength. When kidneys fail, all these functions are disrupted.^[8]

As waste products accumulate in your blood, a condition called uremia develops. This toxic buildup makes you feel sick and can affect your brain function, causing confusion and difficulty concentrating. The inability to remove excess fluid leads to swelling throughout your body and can cause dangerous fluid accumulation in your lungs, making breathing difficult.^[7]

The mineral imbalances that occur with kidney failure create serious complications. Potassium levels can rise dangerously high—a condition called hyperkalemia—which can cause muscle weakness, stiffness, tiredness, and irregular heartbeats that might lead to heart attack. Phosphorus levels also increase, causing a condition called hyperphosphatemia, which can weaken your bones and cause calcium to deposit in blood vessels and organs.^[7]

Without adequate production of a hormone called erythropoietin, your body can’t make enough red blood cells, leading to anemia. This explains the profound fatigue many people with kidney failure experience. Your bones may become weak and brittle because kidneys can no longer activate vitamin D or properly balance calcium and phosphorus. High blood pressure often worsens because kidneys can’t effectively regulate fluid and blood pressure hormones. Many people with kidney failure also develop heart disease and are at increased risk for heart attacks and strokes.^[5]

Prevention Strategies

While you cannot always prevent kidney disease, you can take meaningful steps to reduce your risk and slow progression if you already have early-stage disease. The most important preventive measure is managing conditions that cause kidney damage, particularly diabetes and high blood pressure. Keeping your blood sugar in the target range as much as possible if you have diabetes protects your kidneys from the damaging effects of high glucose levels.^[22]

Controlling blood pressure is equally critical. Healthcare providers generally recommend keeping blood pressure below 140/90 mm Hg, though your doctor may set a different target based on your individual situation. If you have diabetes along with chronic kidney disease, your target may be even lower—below 130/80 mm Hg. Taking prescribed blood pressure medications consistently, even when you feel well, helps prevent further kidney damage.^[11]

Making healthy lifestyle choices supports kidney health in multiple ways. Choose foods that are healthy for your heart and entire body: fresh fruits, fresh or frozen vegetables, whole grains, and low-fat or fat-free dairy products. Cut back on salt and added sugars, aiming for less than 2,300 milligrams of sodium each day. Limit saturated fats and try to keep added sugars to less than 10 percent of your daily calories.^[22]

If you smoke, quitting is one of the best things you can do for your kidneys. Smoking can make kidney disease worse and interferes with medications that lower blood pressure. Limit alcohol consumption to no more than 14 units per week. Maintain a healthy weight, as obesity increases strain on your kidneys and raises your risk of diabetes and high blood pressure. Losing even modest amounts of weight can benefit your kidney health.^[21]

Stay physically active. Regular exercise helps control blood pressure and blood sugar, maintains healthy weight, strengthens bones, improves mood, and may reduce your risk of heart disease. Aim for at least 150 minutes of moderate activity each week. Avoid taking over-the-counter pain medications like NSAIDs (such as ibuprofen) regularly without medical guidance, as these can damage kidneys. Stay well-hydrated and seek prompt treatment for urinary tract infections, which can cause kidney damage if left untreated.^[4]

If you’re at high risk—you have diabetes, high blood pressure, heart disease, or a family history of kidney failure—have regular check-ups that include blood and urine tests to monitor kidney function. Early detection allows for earlier intervention, which can slow or prevent progression to kidney failure. Getting vaccinated, including annual flu shots and the pneumococcal vaccine, helps protect you from infections that can stress your kidneys.^[22]