Your kidneys filter about 50 gallons of blood every day. When they fail, it usually happens slowly and silently over months or years, not overnight. The most common root causes are diabetes and high blood pressure, which together account for the majority of kidney failure cases in the United States. Other causes include autoimmune diseases, genetic conditions, repeated infections, urinary blockages, and certain medications or toxins.
What Does It Actually Mean for Kidneys to Fail?
Kidney failure means your kidneys can no longer filter waste and extra fluid from your blood well enough to keep you healthy. Doctors measure this with two main numbers: your estimated glomerular filtration rate (eGFR) and your urine albumin level.
The eGFR estimates how much filtering capacity you have left. A normal eGFR is generally 90 or higher. Kidney failure is typically defined as an eGFR below 15, at which point dialysis or a kidney transplant becomes necessary to sustain life. This is called end-stage kidney disease, or kidney failure with replacement therapy.
There is an important distinction between acute kidney injury and chronic kidney disease. Acute kidney injury happens suddenly, often over hours or days, and is sometimes reversible if the underlying cause is treated quickly. Chronic kidney disease develops gradually over months to years and generally does not reverse. Both can lead to kidney failure, but through different paths.
One detail many people miss: kidneys rarely fail because of a single event. In most cases, damage accumulates over years. Each hit — high blood sugar, high blood pressure, an infection, a toxic exposure — chips away at function. By the time symptoms appear, a large amount of function is often already gone.
Why Do Kidneys Fail? The Two Biggest Causes
Diabetes and high blood pressure cause the majority of kidney failure cases in the US. Both damage the tiny blood vessels and filtering units inside the kidney, but they do it in different ways.
Diabetes
Persistent high blood sugar damages the glomeruli — the tiny filtering clusters inside each kidney. Over time, this damage makes the filters leaky. Protein that should stay in your blood leaks into your urine. This condition is called diabetic nephropathy.
High blood sugar also thickens the walls of the small blood vessels feeding the kidneys, reducing blood flow. The combination of leaky filters and reduced blood supply steadily erodes kidney function. Diabetes is the leading cause of kidney failure in the US, and it is also one of the most modifiable — blood sugar control and blood pressure control both slow the decline.
High Blood Pressure
High blood pressure damages the kidneys by forcing blood through delicate vessels at too much pressure. Over time, this injures the vessel walls, reducing the kidney’s ability to filter. Damaged kidneys then regulate blood pressure less effectively, which raises blood pressure further. This creates a cycle that accelerates damage in both directions.
High blood pressure is the second leading cause of kidney failure. It is also frequently both a cause and a consequence of kidney disease, which makes early detection important.
What Other Conditions Cause Kidney Failure?
Diabetes and high blood pressure explain most cases, but they are not the only paths to kidney failure. Several other conditions can damage the kidneys directly.
- Glomerulonephritis: Inflammation of the glomeruli, often driven by autoimmune conditions such as lupus. It can also occur after certain infections.
- Polycystic kidney disease: An inherited condition where fluid-filled cysts grow in the kidneys and gradually replace normal tissue.
- Repeated urinary tract infections: Especially when they travel up to the kidneys (pyelonephritis), repeated infections can scar kidney tissue.
- Urinary blockages: Kidney stones, enlarged prostate, or tumors can block urine flow. Backed-up urine raises pressure inside the kidney and damages it over time.
- Certain medications: Long-term use of some pain relievers (particularly NSAIDs), certain antibiotics, and some contrast dyes used in imaging can harm kidneys, especially in people who already have reduced function.
- Heavy metal and toxin exposure: Lead, mercury, and certain industrial chemicals can damage kidney tissue.
- Severe dehydration or blood loss: These reduce blood flow to the kidneys and can cause acute kidney injury, which may progress to chronic damage if repeated.
In some cases, no specific cause is identified. Doctors call this chronic kidney disease of unknown cause, and it is more common in certain populations and regions.
How Does Kidney Damage Progress Over Time?
Chronic kidney disease is staged by eGFR. The stages describe how much filtering capacity remains and help guide treatment decisions.
| Stage | eGFR | What It Means |
|---|---|---|
| Stage 1 | 90 or higher | Normal filtering, but signs of kidney damage (such as protein in urine) |
| Stage 2 | 60–89 | Mildly reduced filtering with signs of damage |
| Stage 3 | 30–59 | Moderately reduced filtering |
| Stage 4 | 15–29 | Severely reduced filtering |
| Stage 5 | Below 15 | Kidney failure; dialysis or transplant needed |
Most people do not progress through every stage. Some stay stable for years. Others decline faster. The rate depends on the underlying cause, how well it is controlled, and individual factors like age and other health conditions.
What makes this tricky is that stages 1 through 3 usually produce no symptoms. You can lose more than half your kidney function and feel completely normal. This is why blood tests matter — they catch problems that symptoms do not.
What Are the Symptoms of Kidney Failure?
Early kidney disease usually has no symptoms. When symptoms do appear, they tend to show up after significant function is already lost.
Common symptoms of advanced kidney failure include:
- Swelling in the legs, ankles, feet, or around the eyes
- Fatigue and weakness
- Shortness of breath
- Nausea and vomiting
- Loss of appetite
- Confusion or difficulty concentrating
- Muscle cramps, especially at night
- Dry, itchy skin
- Changes in urination — more or less frequent, or foamy urine
- Metallic taste in the mouth
These symptoms are not specific to kidney failure. They overlap with many other conditions. That is another reason kidney function is checked with blood and urine tests rather than symptoms alone.
Who Is Most at Risk for Kidney Failure?
Some people face a higher risk than others. The main risk factors are well established.
- Diabetes — the single largest risk factor
- High blood pressure
- Family history of kidney failure
- Age over 60 — kidney function naturally declines somewhat with age
- Obesity
- Heart disease
- Previous acute kidney injury
- Certain racial and ethnic groups — Black Americans, Hispanic Americans, and Native Americans have higher rates of kidney failure, partly due to higher rates of diabetes and high blood pressure and partly due to structural barriers in healthcare access
- Long-term use of certain medications — especially NSAIDs
- Smoking
Having a risk factor does not mean you will develop kidney failure. It means your kidneys should be monitored more closely, typically with blood and urine tests at least once a year.
Can Kidney Failure Be Prevented?
Many cases of kidney failure are preventable or delayable. The most effective steps target the underlying causes.
Controlling blood sugar in diabetes and controlling blood pressure are the two most important things a person can do. Research consistently shows that good control of both slows the progression of kidney disease. Blood pressure control, in particular, has strong evidence behind it for slowing kidney damage across multiple causes.
Other steps supported by evidence include:
- Taking medications as prescribed for diabetes and blood pressure
- Avoiding NSAIDs when possible, especially long-term use
- Not smoking
- Maintaining a healthy weight
- Staying hydrated, unless your doctor has told you to limit fluids
- Getting regular kidney function tests if you have risk factors
Some medications — including certain blood pressure drugs called ACE inhibitors and ARBs, and newer diabetes drugs in the SGLT2 inhibitor class — have been shown in clinical trials to slow kidney disease progression in specific groups. Whether they are appropriate for any individual depends on their overall health and other conditions.
The evidence on diet and kidney disease is more mixed. Reducing sodium intake is widely recommended for blood pressure control, which indirectly helps kidneys. Specific dietary changes for kidney disease should be discussed with a doctor or dietitian, because restricting the wrong nutrients can cause problems.
What Happens When Kidneys Fail Completely?
When kidneys reach stage 5, they can no longer sustain life without help. At that point, treatment options are dialysis, kidney transplant, or in some cases conservative management focused on comfort.
Dialysis does the filtering work that kidneys can no longer do. It comes in two main forms: hemodialysis, usually done at a clinic several times a week, and peritoneal dialysis, which can often be done at home. Neither replaces all kidney functions — the kidneys also produce hormones and regulate other body systems — so dialysis patients often need additional medications and monitoring.
A kidney transplant, when possible, generally offers better long-term outcomes and quality of life than dialysis. However, not everyone is a candidate, and waiting lists can be long. Living donor transplants, when available, often have better outcomes than deceased donor transplants.
Kidney failure is serious, but it is not always the end of the road. Many people live active lives on dialysis or after transplant. The key difference is usually how early the problem was caught and how well the underlying causes were managed.
Frequently Asked Questions
What is the most common cause of kidney failure?
Diabetes is the leading cause of kidney failure in the United States, followed by high blood pressure. Together they account for the majority of cases.
Can kidneys fail suddenly?
Yes, this is called acute kidney injury and it can develop over hours or days. Unlike chronic kidney disease, acute kidney injury is sometimes reversible if the cause is treated quickly.
What are the early warning signs of kidney failure?
There usually are none in the early stages. Most people with early kidney disease feel normal, which is why blood and urine tests are the only reliable way to detect it.
Can kidney failure be reversed?
Chronic kidney failure generally cannot be reversed, but progression can often be slowed significantly with treatment. Acute kidney injury is sometimes reversible depending on the cause and how quickly it is addressed.
