Kidney disease means your kidneys are damaged and can no longer filter blood the way they should. Healthy kidneys remove extra water and waste products from your blood, turning them into urine. When that filtering ability declines, fluid, waste, and harmful substances build up in your body, triggering a cascade of health problems. More than 850 million people worldwide live with some form of kidney disease, making it one of the most common chronic conditions on the planet.
What Your Kidneys Actually Do
Your two kidneys, each about the size of a fist, sit just below your rib cage on either side of your spine. Their primary job is filtering roughly 200 liters of blood every day, pulling out excess water, salts, and metabolic waste to produce urine. But filtration is only part of the picture. Kidneys also regulate blood pressure, signal your bone marrow to produce red blood cells, and help keep your bones strong by managing calcium and phosphorus levels. When kidney disease sets in, all of these functions begin to deteriorate, not just the one most people think of.
Acute vs. Chronic Kidney Disease
Kidney disease falls into two broad categories. Acute kidney injury happens suddenly, often within hours or days. It can result from severe dehydration, a bad infection, a drug reaction, or a physical trauma like a crush injury. In many cases, acute kidney injury is reversible with prompt treatment.
Chronic kidney disease (CKD) develops slowly over months or years and is generally not reversible. It progresses through stages based on how well your kidneys filter blood, measured by a value called the glomerular filtration rate (GFR). A GFR of 60 or above is considered normal. Below 60 signals kidney disease, and a GFR of 15 or less is classified as kidney failure.
These two categories are more connected than doctors once believed. Research published in the New England Journal of Medicine showed that even a mild episode of acute kidney injury can increase the long-term risk of developing chronic kidney disease. Patients who appeared to recover full kidney function after an acute episode often went on to develop progressive CKD years later. Repeated injuries compound the risk further.
Leading Causes
Diabetes is the single biggest driver of kidney disease, responsible for 46% of all new kidney failure cases in the United States between 2019 and 2021. High blood sugar damages the tiny blood vessels inside the kidneys over time, slowly destroying their filtering capacity. High blood pressure is the second leading cause, accounting for another 29% of new cases. Together, these two conditions explain roughly three out of every four kidney failure diagnoses.
The third most common cause is a group of conditions called glomerulonephritis, where inflammation damages the kidney’s filtering units directly. Other contributors include polycystic kidney disease (a genetic condition that causes fluid-filled cysts to grow in the kidneys), prolonged use of certain over-the-counter pain relievers, recurrent urinary tract infections, and kidney stones that cause blockages.
Why Most People Don’t Know They Have It
Kidney disease is often called a “silent” condition because it produces no noticeable symptoms in its early stages. You can lose a significant portion of kidney function and feel perfectly fine. This is one of the reasons CKD is so dangerous: by the time symptoms appear, the disease is usually advanced.
When symptoms do develop, they tend to be vague and easy to attribute to something else. Common late-stage signs include swelling in your feet and ankles, persistent fatigue, nausea, loss of appetite, dry and itchy skin, muscle cramps, urinating more or less than usual, and shortness of breath. None of these are unique to kidney disease, which makes diagnosis tricky without blood and urine tests.
How Kidney Disease Is Detected
Two simple tests catch most cases. A blood test estimates your GFR by measuring a waste product called creatinine. If your kidneys are struggling to filter, creatinine levels rise. A urine test checks for albumin, a protein that healthy kidneys keep in the blood. Finding albumin in urine is an early warning sign that the kidneys’ filters are leaking. A result under 30 micrograms per milligram of creatinine is normal. Between 30 and 300 indicates early kidney damage. Above 300 points to more significant disease.
Because kidney disease is so often symptomless, routine screening matters, especially if you have diabetes, high blood pressure, a family history of kidney problems, or are over 65. Among American Medicare beneficiaries over 65, the prevalence of CKD is 13.5%.
Complications Beyond the Kidneys
Failing kidneys create problems throughout the body. One of the most common complications is anemia, a shortage of red blood cells. Healthy kidneys produce a hormone that tells your bone marrow to make red blood cells. As kidney function drops, production of that hormone falls too, leaving you fatigued, short of breath, and unable to exercise the way you used to. Chronic inflammation from kidney disease also makes it harder for your body to absorb and use iron, compounding the problem. Anemia in CKD is more than an inconvenience: it’s an independent risk factor for heart disease, stroke, and death.
Kidney disease also disrupts your body’s ability to manage minerals like calcium and phosphorus, leading to weakened bones and calcification of blood vessels. Potassium and acid levels can climb in the blood, straining the heart. Fluid retention raises blood pressure further, creating a cycle where kidney damage and cardiovascular disease feed each other.
Managing CKD Before It Progresses
In earlier stages, the goal is to slow progression and protect remaining kidney function. Because diabetes and high blood pressure cause most cases, keeping blood sugar and blood pressure under control is the single most effective strategy. Medications that lower blood pressure also reduce stress on the kidneys’ delicate filters.
Diet plays a significant role. For people with stage 3 CKD or beyond, sodium intake is generally recommended at 2,300 milligrams or less per day, roughly one teaspoon of salt. Depending on your lab results, you may also need to limit potassium (found in bananas, potatoes, and tomatoes) and phosphorus (found in dairy, processed foods, and dark sodas). Protein intake sometimes needs adjustment as well, since damaged kidneys struggle to handle the waste products that come from digesting protein.
Staying physically active, maintaining a healthy weight, not smoking, and avoiding over-the-counter pain relievers that stress the kidneys (like ibuprofen and naproxen) all help preserve function over time.
Treatment for Kidney Failure
When kidneys lose nearly all their filtering ability, the condition is called end-stage renal disease. At this point, survival depends on replacing kidney function through dialysis or a transplant.
Dialysis does the job your kidneys can no longer handle, filtering waste and extra fluid from your blood using a machine or a special solution. The most common form involves visiting a dialysis center several times a week for sessions lasting a few hours each. Another option uses the lining of your abdomen as a natural filter, which can be done at home, often overnight.
A kidney transplant is generally the preferred treatment when possible. A healthy kidney from a living or deceased donor is surgically placed in your body, and if successful, it takes over full filtering duties. Transplant recipients need to take medications for life to prevent their immune system from rejecting the new organ, but quality of life and long-term survival are typically better than with ongoing dialysis.
Without either dialysis or a transplant, kidney failure is fatal. The timeline varies, but the disease will eventually progress to the point where the body can no longer sustain itself.