Chronic kidney disease (CKD) has five stages, numbered 1 through 5, with stage 3 split into two substages (3a and 3b), giving six distinct categories in total. Each stage corresponds to how well your kidneys filter waste from your blood, measured by a number called the estimated glomerular filtration rate, or eGFR. A healthy eGFR is 90 or above, and it drops as kidney function declines.
How the Five Stages Break Down
The staging system is built around your eGFR, which estimates how many milliliters of blood your kidneys can filter per minute. Here’s what each stage looks like:
- Stage 1: eGFR of 90 or higher. Kidney function is normal or near-normal, but there’s evidence of damage from other signs like protein in the urine or structural abnormalities on imaging.
- Stage 2: eGFR of 60 to 89. A mild decrease in function, again with evidence of kidney damage present.
- Stage 3a: eGFR of 45 to 59. Mild to moderate loss of function.
- Stage 3b: eGFR of 30 to 44. Moderate to severe loss of function.
- Stage 4: eGFR of 15 to 29. Severe loss of function.
- Stage 5: eGFR below 15, or on dialysis. This is kidney failure.
One important detail: stages 1 and 2 require evidence of actual kidney damage beyond just the eGFR number. Someone with an eGFR of 95 and no signs of damage doesn’t have CKD. That evidence typically comes from blood and urine tests that detect protein or small amounts of blood in the urine, or from imaging that reveals structural problems with the kidneys.
Why Stage 3 Is Split in Two
Stage 3 covers a wide range of kidney function, from mildly reduced to approaching severe. Splitting it into 3a (eGFR 45 to 59) and 3b (eGFR 30 to 44) helps distinguish between people who are relatively stable and those who are closer to needing more aggressive management. Someone at 3a may have no symptoms at all, while someone at 3b is more likely to develop complications and needs closer monitoring.
Albuminuria Adds a Second Layer
Your eGFR tells half the story. The other half is how much protein (specifically albumin) is leaking into your urine, which signals ongoing kidney damage. This is measured by something called the albumin-to-creatinine ratio, and it falls into three categories:
- A1: Less than 30 mg/g. Normal to mildly increased.
- A2: 30 to 300 mg/g. Moderately increased.
- A3: Greater than 300 mg/g. Severely increased.
Two people can be at the same eGFR stage but have very different outlooks depending on their albuminuria category. Higher albumin levels mean faster progression and greater risk of complications. Your doctor uses both numbers together to get the full picture.
What You Feel at Each Stage
Stages 1 and 2 are essentially silent. Your kidneys are still doing most of their job, and you’re unlikely to notice anything wrong. Most people at these stages only find out through routine lab work, especially if they’re being screened because of diabetes or high blood pressure.
Stage 3 is where some people begin to notice vague symptoms like fatigue or changes in urination, though many still feel fine. The kidneys are working hard enough to keep waste products mostly in check, but subtle imbalances in minerals and hormones may start to develop.
Stage 4 is when symptoms become common and often hard to ignore. The National Kidney Foundation lists a long set of possible symptoms at this stage: fatigue, trouble concentrating, itchy or dry skin, numbness or swelling in the arms and legs, muscle cramps, shortness of breath, nausea, loss of appetite, trouble sleeping, and breath that smells like ammonia. Stage 4 is also when metabolic complications tend to appear, including anemia, a buildup of acid in the blood, imbalances in calcium and phosphorus that weaken bones, and dangerously high potassium levels.
Stage 5, kidney failure, means the kidneys can no longer sustain life on their own. Waste products accumulate in the blood, and without treatment, this stage is fatal.
What Drives Progression Between Stages
CKD doesn’t always progress. Some people stay at the same stage for years or even decades. The speed at which kidney function declines depends largely on whether the underlying causes are controlled.
Diabetes is the single biggest driver. Roughly 1 in 3 adults with diabetes has CKD, because chronically high blood sugar damages the tiny blood vessels and filters inside the kidneys. High blood pressure is the second major factor, affecting about 1 in 5 adults with hypertension. Elevated pressure narrows blood vessels throughout the body, including in the kidneys, and the resulting damage creates a vicious cycle: injured kidneys can’t regulate fluid properly, which pushes blood pressure even higher. Heart disease contributes too, because reduced blood flow to the kidneys accelerates their decline. Obesity raises risk indirectly by increasing the likelihood of both diabetes and high blood pressure.
Keeping blood sugar and blood pressure well controlled is the most effective way to slow or stall progression. For many people at stages 1 through 3, these lifestyle and medication strategies can preserve kidney function for years.
Treatment Options at Stage 5
When kidney function drops to an eGFR of 5 to 10, most people start feeling sick enough that treatment becomes necessary. There are four main paths:
- Hemodialysis uses a machine to filter your blood through an external device, removing waste products your kidneys can no longer handle. This typically happens three times a week at a dialysis center, though home options exist.
- Peritoneal dialysis uses the lining of your abdomen as a natural filter. Fluid is introduced into the belly, absorbs waste, and is then drained. Many people do this at home, often overnight.
- Kidney transplant places a healthy kidney from a living or deceased donor into your body. A successful transplant eliminates the need for dialysis.
- Conservative management focuses on controlling symptoms and maintaining quality of life without dialysis or transplant. This is sometimes chosen by people who prefer comfort-focused care.
How Your Stage Is Determined
Staging relies on a simple blood test that measures creatinine, a waste product from normal muscle activity. A formula adjusts the result for your age and sex to estimate your eGFR. A urine test checks for albumin. Together, these two numbers place you on the CKD grid. Because eGFR can fluctuate day to day, a CKD diagnosis typically requires abnormal results sustained over at least three months.
If you’ve had your kidney function tested and received a stage number, the eGFR ranges above can help you understand where you fall and what that means for your health going forward.