There are five stages of chronic kidney disease (CKD), ranging from mild kidney damage with normal function at Stage 1 to complete kidney failure at Stage 5. Each stage is defined by how well your kidneys filter your blood, measured by a number called the estimated glomerular filtration rate, or eGFR. This number comes from a simple blood test and tells your doctor what percentage of normal kidney function you still have.
How the Five Stages Are Defined
Your eGFR measures how many milliliters of blood your kidneys filter per minute. A healthy kidney filters 90 or more. As that number drops, the stage goes up:
- Stage 1 (eGFR 90 or above): Kidney function is normal, but there are signs of damage, such as protein leaking into the urine.
- Stage 2 (eGFR 60 to 89): Mild loss of kidney function with evidence of damage.
- Stage 3a (eGFR 45 to 59): Mild to moderate loss of function.
- Stage 3b (eGFR 30 to 44): Moderate to severe loss of function.
- Stage 4 (eGFR 15 to 29): Severe loss of function.
- Stage 5 (eGFR below 15): Kidney failure, sometimes called end-stage renal disease.
You’ll notice Stage 3 is split into two sub-stages. That’s because the jump from an eGFR of 59 down to 30 covers a wide range, and the risks change significantly within it. Stage 3a is when complications like anemia, bone disease, and acid buildup in the blood can first appear, though the risk is still low. By Stage 3b, those complications become more likely, and the risk of progressing to later stages increases.
Why Early Stages Often Go Unnoticed
Most people with kidney disease have no symptoms until the very last stages. Stages 1 and 2 are typically discovered by accident, during routine blood work or a urine test that reveals protein where it shouldn’t be. Your kidneys have so much built-in capacity that losing 30 or even 40 percent of their filtering ability may not produce any noticeable changes in how you feel.
As kidney function drops further, particularly in Stage 4 and beyond, symptoms start to surface. These include nausea, loss of appetite, swelling in the feet and ankles, dry and itchy skin, muscle cramps, shortness of breath, trouble sleeping, and urinating too much or too little. By Stage 5, additional problems like fatigue, decreased mental sharpness, and high blood pressure that’s difficult to control become common.
GFR Isn’t the Only Measurement That Matters
Doctors don’t rely on eGFR alone. They also check how much protein (specifically albumin) is leaking into your urine, using a test called the urine albumin-to-creatinine ratio. This is graded on its own scale: A1 means normal to mildly increased protein levels (under 30 mg/g), A2 means moderately increased (30 to 300 mg/g), and A3 means severely increased (over 300 mg/g).
This matters because two people can have the same eGFR but very different outlooks. Someone at Stage 2 with high albumin in their urine faces a greater risk of progression than someone at Stage 2 with normal albumin levels. Together, the GFR stage and the albumin category give a much clearer picture of how your kidneys are doing and where they’re headed.
What Happens at Stage 5
Stage 5 means your kidneys are functioning at less than 15 percent of their normal capacity. At this point, your kidneys can no longer remove enough waste and fluid from your blood to keep you alive without help. There are three paths forward: a kidney transplant, dialysis, or supportive (palliative) care focused on managing symptoms.
A transplant, when possible, is generally the preferred option over a lifetime of dialysis. Dialysis takes over the kidneys’ core jobs: removing waste, balancing electrolyte levels, and helping control blood pressure. Some people receive dialysis as a bridge while waiting for a transplant. Without either treatment, kidney failure is fatal.
What Speeds Up Progression
Kidney disease doesn’t always march from one stage to the next. Some people stay at the same stage for decades, while others progress quickly. The difference often comes down to a handful of factors you can influence.
Uncontrolled high blood pressure is both a cause and a consequence of CKD, and it directly accelerates the loss of kidney function. The same is true for uncontrolled blood sugar in people with diabetes. Optimal glucose control before kidney disease develops can help prevent it, though once damage has started, tightening glucose control may have a smaller effect on progression. Smoking is associated with worsening protein levels in the urine and faster progression, on top of raising the risk of stroke and heart attack in people who already have CKD.
Diet plays a role too. Keeping sodium intake under 2,300 mg per day helps manage blood pressure. Eating adequate but not excessive protein (roughly 0.8 grams per kilogram of body weight daily) may lower albumin in the urine and slow progression. As kidney function declines, phosphorus and potassium can build up in the blood because the kidneys can no longer clear them efficiently. High phosphorus weakens bones over time. Whether you need to limit these minerals depends on your blood test results and the stage you’re in, so the specifics vary from person to person.
Regular physical activity, at least 20 to 30 minutes a day of both aerobic and strength training, helps prevent cardiovascular disease, improves blood sugar control, and maintains muscle mass. People with CKD tend to become less active, but the recommended goals are the same as for the general population.