Chronic kidney disease (CKD) is classified into five stages based on how well your kidneys filter blood. The key measurement is your estimated glomerular filtration rate, or eGFR, which shows the percentage of normal kidney function you have. A higher number means healthier kidneys, and a lower number means more damage.
About 14% of U.S. adults have some form of kidney disease, but most don’t know it. The earlier stages rarely cause symptoms, which is why staging matters: it tells you and your doctor where things stand before you feel anything is wrong.
How Kidney Function Is Measured
Your eGFR comes from a simple blood test that measures creatinine, a waste product your muscles produce. Your doctor plugs that number into a formula along with your age and sex to estimate how many milliliters of blood your kidneys filter per minute. A healthy kidney filters about 90 mL/min or more. As that number drops, so does your stage.
Kidney disease staging also factors in albuminuria, which is the amount of a protein called albumin leaking into your urine. Healthy kidneys keep albumin in the blood, so finding it in urine signals damage even when your eGFR looks normal. Albuminuria is measured through a urine test and classified into three categories:
- A1 (normal): less than 30 mg/g
- A2 (moderately increased): 30 to 300 mg/g
- A3 (severely increased): more than 300 mg/g
Your full CKD classification combines both numbers. Someone with an eGFR of 50 and an A1 albumin level faces a different outlook than someone with the same eGFR but A3 albuminuria. Higher albumin levels dramatically increase the risk of both kidney disease progression and heart disease.
Stage 1: Normal Filtration With Early Damage
eGFR: 90 or above
At stage 1, your kidneys filter blood at a normal rate, but there’s evidence of damage, usually albumin in the urine or structural changes visible on imaging. You won’t feel any symptoms. About 65.5% of U.S. adults fall into this eGFR range, though most of them have no kidney damage at all. The ones classified as stage 1 CKD are those with abnormal urine or imaging results despite their normal filtration rate.
Stage 2: Mildly Decreased Function
eGFR: 60 to 89
Stage 2 represents a mild drop in filtration. Like stage 1, it produces no noticeable symptoms. Many people in this range are older adults whose kidney function has declined naturally with age. The distinction between normal aging and true CKD again comes down to whether there’s albumin in the urine or other signs of kidney damage. Without those markers, a mildly low eGFR alone isn’t considered kidney disease.
Stage 3a and 3b: The Critical Middle Stages
Stage 3 is where kidney disease becomes clinically significant, and it’s split into two substages because the risk profile changes meaningfully within this range.
Stage 3a
eGFR: 45 to 59
Stage 3a means mild to moderate loss of kidney function. About 4% of U.S. adults are in this category. Most people still feel fine, but the risk of heart disease rises even if albumin levels are normal. This is the stage where your doctor will likely start monitoring your kidney function more closely and may recommend changes to your diet, blood pressure management, or medications that protect kidney function.
Stage 3b
eGFR: 30 to 44
Stage 3b is a moderate to severe decrease. About 1.1% of adults reach this level. Some people begin noticing subtle symptoms here: fatigue, mild swelling in the ankles, or changes in how often they urinate. The risk of progressing to kidney failure increases substantially, and managing blood pressure and blood sugar (if you have diabetes) becomes more urgent.
Stage 4: Severe Loss of Function
eGFR: 15 to 29
Stage 4 means your kidneys are working at roughly 15% to 29% of normal capacity. This is the stage where symptoms typically become harder to ignore. You may experience nausea, loss of appetite, muscle cramps, swelling in the feet and ankles, dry and itchy skin, shortness of breath, trouble sleeping, or urinating too much or too little. These symptoms happen because your kidneys can no longer keep up with filtering waste and balancing fluids.
Only about 0.3% of U.S. adults are in stage 4. At this point, your medical team will begin preparing you for the possibility of dialysis or a kidney transplant. That doesn’t mean you’ll need them immediately, but planning ahead gives you better options if your function continues to decline.
Stage 5: Kidney Failure
eGFR: below 15
Stage 5 is kidney failure, sometimes called end-stage kidney disease. Your kidneys have less than 15% of their normal function, which is life-threatening without treatment. At this stage, dialysis (a machine that filters your blood for you) or a kidney transplant becomes necessary to survive.
About 0.15% of U.S. adults are in stage 5. The symptoms from stage 4 intensify, and new ones can appear, including confusion, severe fatigue, and difficulty concentrating as toxins build up in the blood.
How Quickly Kidney Disease Progresses
Kidney disease doesn’t follow a fixed timeline. Some people stay in stage 3 for decades and never reach stage 4. Others progress more quickly, especially if they have uncontrolled diabetes, high blood pressure, or high levels of albumin in their urine. The combination of your eGFR stage and your albuminuria category is the best predictor of how fast things will move.
For context, someone in stage 3a with normal albumin levels (A1) has a relatively low risk of progression. But someone in the same eGFR range with severely increased albumin (A3) faces a much steeper trajectory. This is why two people with the same eGFR number can have very different outlooks.
What You Can Do at Each Stage
The earlier the stage, the more influence you have over the disease’s course. In stages 1 and 2, the focus is on controlling the underlying cause, most commonly high blood pressure or diabetes. Keeping blood pressure within your target range is one of the single most effective things you can do to slow kidney damage.
In stages 3 and 4, dietary changes become more important. Your doctor may recommend adjusting your intake of sodium, potassium, and phosphorus, all of which become harder for weakened kidneys to regulate. Protein intake may also need to be modified, since processing protein generates waste your kidneys must filter.
At every stage, avoiding medications that stress the kidneys (like certain over-the-counter pain relievers taken regularly) and staying hydrated helps protect the function you still have. Smoking accelerates kidney damage, and quitting meaningfully slows progression regardless of what stage you’re in.