Chronic kidney disease (CKD) is a long-term condition in which your kidneys gradually lose their ability to filter waste and excess fluid from your blood. It affects roughly 14% of adults worldwide, and most people in the early stages have no idea they have it. The disease is defined by at least three months of reduced kidney function, measured by how well your kidneys filter blood or by the presence of protein leaking into your urine.
How CKD Is Diagnosed
Doctors diagnose CKD using two main tests. The first is a blood test that estimates your glomerular filtration rate (eGFR), which tells you how efficiently your kidneys are cleaning your blood. A normal eGFR is 100 or above. A result below 60 suggests kidney disease. The second test checks for albumin in your urine. Albumin is a protein that healthy kidneys keep in your blood. A urine albumin level above 30 mg/g signals possible kidney damage.
Either an eGFR below 60 or albumin above 30 mg/g, lasting for three months or more, is enough for a CKD diagnosis. Many people are diagnosed through routine bloodwork for another condition, particularly diabetes or high blood pressure, rather than because they felt something was wrong.
The Five Stages of CKD
CKD is classified into five stages based on your eGFR number. Higher stages mean more severe damage:
- Stage 1: eGFR 90 to 100. Kidney function is nearly normal, but there are signs of damage (like protein in the urine).
- Stage 2: eGFR 60 to 89. A mild decrease in function.
- Stage 3: eGFR 30 to 59. Moderate loss of function. This is the stage where complications can start developing.
- Stage 4: eGFR 15 to 29. Severe loss of function. Planning for dialysis or transplant typically begins here.
- Stage 5: eGFR below 15. This is kidney failure, sometimes called end-stage renal disease. The kidneys can no longer sustain life without dialysis or a transplant.
Progression through these stages is not inevitable. With the right management, many people stay in the same stage for years or even decades.
What Causes It
Diabetes and high blood pressure are responsible for the majority of CKD cases. About 1 in 3 adults with diabetes and 1 in 5 adults with high blood pressure may develop chronic kidney disease. Each kidney contains millions of tiny filters called nephrons. Sustained high blood sugar damages the blood vessels supplying those filters, while high blood pressure puts constant mechanical stress on them. Many people with diabetes also develop high blood pressure, compounding the damage.
Other causes include glomerulonephritis (inflammation of the kidney’s filtering units), polycystic kidney disease (a genetic condition that causes fluid-filled cysts to grow in the kidneys), recurrent kidney infections, prolonged obstruction from kidney stones or an enlarged prostate, and long-term use of certain pain medications. Sometimes no single cause is identified.
Why Symptoms Take So Long to Appear
CKD is often called a “silent” disease because you can lose a significant amount of kidney function before anything feels different. Most people don’t notice symptoms until the disease is severe, typically stage 4 or 5. Your kidneys have so much built-in reserve that the remaining healthy tissue compensates for what’s been lost, masking the problem.
When symptoms do appear, they tend to be vague enough to blame on other things. The earliest noticeable signs are often swelling in the hands, feet, or ankles, itchy skin, or needing to urinate more frequently than usual (especially at night). As function declines further, you may experience:
- Persistent fatigue and low energy
- Foamy or bubbly urine (from excess protein)
- Puffy eyes, particularly in the morning
- Loss of appetite, nausea, or vomiting
- Shortness of breath
- Muscle cramps
- Trouble concentrating or sleeping
- Dry, darkening skin
Because symptoms arrive late, screening through bloodwork is the only reliable way to catch CKD early, particularly if you have diabetes, high blood pressure, heart disease, or a family history of kidney problems.
Complications Beyond the Kidneys
As kidney function drops, the effects ripple through other systems in your body. Two of the most common complications are anemia and bone disease.
Healthy kidneys produce a hormone that signals your bone marrow to make red blood cells. Damaged kidneys make less of it, leading to anemia, which is the main reason CKD causes such persistent fatigue and weakness. Inflammation from CKD also triggers the liver to produce a hormone called hepcidin, which locks iron inside storage cells and prevents your body from using it to build new red blood cells. So even if you have enough iron in your body, your bone marrow can’t access it.
CKD also disrupts the balance of calcium, phosphorus, and vitamin D that keeps your bones strong. Damaged kidneys struggle to activate vitamin D and can’t clear excess phosphorus efficiently. Over time, this leads to weakened bones, stiff blood vessels, and a higher risk of fractures. You might not feel bone disease directly, but it contributes to the muscle cramps, joint pain, and general weakness that many people with advanced CKD experience.
Heart disease is the leading cause of death in people with CKD. The fluid overload, high blood pressure, and mineral imbalances that come with failing kidneys all place extra strain on the heart. This is why managing CKD aggressively is about protecting your heart as much as your kidneys.
How CKD Is Managed
There is no cure for CKD, but treatment focuses on slowing progression and preventing complications. The specific approach depends on your stage and what caused the disease.
Blood pressure control is the single most important intervention for nearly everyone with CKD. Keeping blood pressure within target range reduces the strain on your kidney filters and slows further damage. If you have diabetes, tight blood sugar management is equally critical.
A class of medications originally designed for type 2 diabetes has become a major tool for protecting kidney function. In a large real-world study from Japan, patients taking these drugs had a 60% lower rate of major kidney events compared to those on other medications, and a 74% lower risk of reaching kidney failure. These drugs appear to reduce pressure inside the kidney filters and lower inflammation, benefits that extend even to people without diabetes.
Dietary Changes
There is no single CKD diet. In the early stages, you may have very few restrictions. As the disease progresses, your nutritional needs shift and certain nutrients become harder for your kidneys to handle. The general principles include keeping sodium below 2,300 milligrams a day (and often lower), and working with a dietitian to find the right balance of protein. Too much protein generates waste products your kidneys must filter, but too little leads to muscle loss. Potassium and phosphorus may also need to be limited in later stages, since damaged kidneys can’t clear the excess efficiently.
The key takeaway is that dietary management gets more specific as CKD advances. What works at stage 2 may be wrong for stage 4. A renal dietitian can tailor your eating plan to your lab results rather than applying blanket rules.
What Kidney Failure Looks Like
If CKD progresses to stage 5, your kidneys can no longer keep you alive on their own. At this point, you need either dialysis or a kidney transplant. Dialysis takes over the job of filtering your blood. Hemodialysis typically requires three sessions per week at a clinic, each lasting about four hours. Peritoneal dialysis can be done at home, using the lining of your abdomen as a natural filter.
A kidney transplant, when available, generally offers a better quality of life and longer survival than long-term dialysis. Transplanted kidneys can come from living or deceased donors, and the wait for a deceased donor kidney varies widely by region. Planning for these options usually begins at stage 4, well before kidney function drops to critical levels, so you have time to make informed decisions rather than starting dialysis as an emergency.
Not everyone with CKD reaches stage 5. Many people, especially those diagnosed early and managed well, live full lives with stable kidney function. The earlier you know about it, the more you can do to change its trajectory.