Chronic kidney disease (CKD) is classified into five stages based on how well your kidneys filter waste from your blood, measured by a number called estimated glomerular filtration rate (eGFR). A healthy eGFR is 90 or above. As that number drops, the stage increases, and kidney function worsens. Most people have no symptoms until the later stages, which is why routine blood and urine tests are the primary way kidney disease gets caught.
How Kidney Function Is Measured
Your eGFR is calculated from a simple blood test that measures creatinine, a waste product your muscles produce. The lab plugs that value into a formula along with your age and sex to estimate how many milliliters of blood your kidneys filter per minute. A newer blood marker called cystatin C can also be used and is sometimes more accurate, particularly for older adults or people with multiple health conditions. In one large study, about 27% of patients were reclassified to a more advanced stage of CKD when cystatin C was used instead of creatinine alone.
Staging also factors in how much protein is leaking into your urine, measured by a spot urine test called the albumin-to-creatinine ratio (ACR). Normal is below 30 mg/g. Moderately increased protein (30 to 300 mg/g) signals early kidney damage, and severely increased protein (above 300 mg/g) raises the risk of progression significantly. Two people with the same eGFR can have very different outlooks depending on how much protein is in their urine.
Stage 1: Normal Filtration With Signs of Damage
In stage 1, your eGFR is 90 or higher, which is technically normal. The reason it still counts as kidney disease is that there’s evidence of damage: protein in the urine, blood in the urine, abnormal imaging findings, or structural problems detected on ultrasound. Your kidneys are still doing their job, but something is injuring them. Persistent protein in the urine is a defining marker of kidney injury regardless of eGFR.
Most people at this stage feel completely fine and discover the problem only through routine lab work. The focus here is identifying and treating the underlying cause, whether that’s diabetes, high blood pressure, or something else, to prevent further decline.
Stage 2: Mildly Reduced Function
Stage 2 means your eGFR has dropped to between 60 and 89. Like stage 1, a diagnosis requires evidence of kidney damage beyond the eGFR number itself, since many healthy people naturally fall into this range, especially as they age. Symptoms are still rare at this point.
The clinical distinction between stages 1 and 2 matters mostly for tracking trends over time. If your eGFR is slowly declining from one test to the next and you have protein in your urine, that trajectory tells your doctor more than any single number.
Stage 3: Where Complications Start
Stage 3 is where kidney disease becomes more clinically significant. Your eGFR is between 30 and 59, meaning your kidneys are filtering at roughly half capacity or less. This is the most commonly diagnosed stage, often the point where people first learn they have CKD.
Stage 3 is split into two substages. Stage 3a means an eGFR between 45 and 59, representing mild-to-moderate loss. Stage 3b means an eGFR between 30 and 44, which is moderate-to-severe. The distinction matters because the risk of complications and progression to kidney failure rises substantially once you cross below 45.
At this stage, waste products can begin building up in your blood, and you may notice early symptoms: fatigue, weakness, swelling in your hands or feet. Complications like high blood pressure that’s harder to control, weakening bones from disrupted mineral balance, and early anemia can emerge. When kidney function drops, your body has trouble regulating phosphorus, which triggers your parathyroid glands to pull calcium out of your bones. Over time, this makes bones weaker and more prone to fractures.
Stage 4: Severe Loss of Function
Stage 4 means your eGFR is between 15 and 29. Your kidneys are severely impaired, and symptoms become more noticeable and harder to manage. Nausea, loss of appetite, persistent fatigue, difficulty concentrating, and fluid retention are common. A sudden increase in body weight can signal fluid buildup, which may also cause swelling in the legs or shortness of breath if fluid collects in the lungs.
This is the stage where planning for the future becomes critical. Your care team will typically begin discussing whether dialysis or a kidney transplant may eventually be needed, and if transplant is an option, the evaluation process can take months, so starting early is important. Some people begin the search for a living donor at this point.
Dietary adjustments become more specific in stage 4. As kidney function declines, your body has a harder time handling excess phosphorus, potassium, and protein. There’s no single diet that applies to everyone with CKD. The right plan depends on your weight, age, blood test results, and how much protein is in your urine. Eating too much protein stresses the kidneys, but eating too little leads to muscle loss, so the balance is individual.
Stage 5: Kidney Failure
Stage 5, sometimes called end-stage renal disease, means your eGFR has fallen below 15. Your kidneys can no longer keep up with the body’s needs. Symptoms at this stage can be severe: nausea and vomiting, extreme fatigue, trouble thinking clearly, difficulty sleeping, persistent itching, and blood pressure that resists medication. Inflammation around the heart (pericarditis) and nervous system changes, including personality shifts or difficulty concentrating, can occur in the final stages.
Dialysis or a transplant becomes necessary to survive. International guidelines generally recommend starting dialysis when symptoms of advanced kidney failure appear, which typically happens when eGFR falls into the 5 to 10 range, though some guidelines use an eGFR of 6 as a threshold. The timing isn’t purely about numbers. If symptoms are manageable and you’re being closely monitored, some approaches intentionally defer dialysis as long as safely possible.
Two types of dialysis exist. Hemodialysis filters your blood through a machine, usually at a clinic three times a week for several hours per session. Peritoneal dialysis uses the lining of your abdomen as a filter and can often be done at home, including overnight. A kidney transplant, when available, generally offers a better long-term quality of life than dialysis, but not everyone is a candidate.
How Quickly CKD Progresses
The speed of progression varies enormously. Some people stay in stage 3 for decades without ever reaching kidney failure. Others move through the stages in just a few years. The biggest factors influencing speed are how well blood pressure and blood sugar are controlled, whether there’s significant protein in the urine, and what’s causing the kidney disease in the first place.
The combination of eGFR stage and urine protein level together predicts risk far better than either one alone. Someone in stage 3a with normal urine protein has a very different outlook than someone in stage 3a with severely elevated protein. This is why doctors track both numbers at every visit. A stable eGFR and low protein in the urine, even at a moderate stage, is a reassuring pattern. A falling eGFR with rising protein levels is the combination that warrants the most aggressive management.