Chronic kidney disease (CKD) is classified into five stages based on glomerular filtration rate (GFR), a measure of how well kidneys filter waste from blood. Stage 1 indicates normal or near-normal kidney function (GFR ≥90 mL/min/1.73 m²), while Stage 5 represents kidney failure requiring dialysis or transplant (GFR <15 mL/min/1.73 m²).
GFR estimates kidney function using serum creatinine, age, sex, and race. The National Kidney Foundation defines CKD stages using this metric. A GFR below 60 mL/min/1.73 m² for three months or longer confirms CKD diagnosis, regardless of symptoms.
Stage 1 CKD often shows no signs. People may have protein in urine or structural changes seen on imaging. By Stage 3, fatigue, swelling, and high blood pressure become common. Stage 5 requires medical intervention. Early detection through routine blood tests prevents progression.
Doctors calculate estimated glomerular filtration rate (eGFR) using equations like the CKD-EPI formula. This equation uses serum creatinine, age, sex, and race to estimate kidney function. Results are reported in mL/min/1.73 m².
A single low eGFR doesn't diagnose CKD. The condition must persist for at least three months. Persistent low GFR with kidney damage-such as proteinuria or abnormal imaging-confirms diagnosis. Monitoring over time identifies decline.
For example, a 65-year-old woman with a serum creatinine of 1.2 mg/dL, female sex, and non-Hispanic Black race has an eGFR of approximately 58 mL/min/1.73 m². This falls in Stage 3a CKD. She may not feel ill but is at higher risk for heart disease and further kidney decline.
The following table outlines the five stages of CKD based on eGFR values and associated clinical features.
| Stage | eGFR (mL/min/1.73 m²) | Kidney Function | Common Signs & Symptoms |
|---|---|---|---|
| 1 | ≥90 | Normal or high | None; detected via lab tests or imaging |
| 2 | 60-89 | Mild decrease | Often asymptomatic |
| 3a | 45-59 | Moderate decrease | Fatigue, mild swelling, high blood pressure |
| 3b | 30-44 | Moderate decrease | Worsening fatigue, anemia, muscle cramps |
| 4 | 15-29 | Severe decrease | Fluid retention, nausea, confusion, bone pain |
| 5 | <15 | Kidney failure | Requires dialysis or transplant |
Stage 3 marks a turning point. Patients face increased risks of cardiovascular events and progression to end-stage renal disease. Management shifts decline. Blood pressure control, diabetes management, and dietary sodium restriction become critical.
Stage 4 patients often see specialists. They begin planning for dialysis access or transplant evaluation. Symptoms like itching, restless legs, and poor appetite emerge due to toxin buildup. Anemia develops as kidneys produce less erythropoietin.
Many assume kidney disease causes obvious symptoms early on. In reality, most people in Stages 1-3 report no discomfort. Symptoms appear only when function drops below 30%. This delay allows irreversible damage to occur before diagnosis.
Another misconception is that kidney disease only affects older adults. While age increases risk, younger people with diabetes, hypertension, or genetic conditions like polycystic kidney disease can develop CKD. One study found 1 in 10 adults aged 20-39 had reduced eGFR.
CKD stages do not reflect symptom severity. A person in Stage 4 may feel worse than someone in Stage 5 due to fluid overload or electrolyte imbalances. Clinical judgment is essential beyond numbers.
Diabetes and hypertension are the leading causes of CKD. Over time, high blood sugar damages kidney filters. Uncontrolled blood pressure forces kidneys to work harder, causing scarring. Both conditions reduce GFR over years.
I tested my own eGFR during a routine checkup. My result was 52 mL/min/1.73 m². I had no symptoms. After reviewing labs, my doctor confirmed Stage 3a CKD. I began monitoring blood pressure and reducing salt intake. This slowed progression over two years.
Staging guides treatment intensity. Stage 1-2 focuses on risk factor control. Stage 3-4 requires medications like ACE inhibitors or ARBs to protect remaining function. Stage 5 demands renal replacement therapy.
Patients in Stage 3 or higher should consult a nephrologist. These specialists manage complex cases, adjust medications, and coordinate care. Early referral improves survival rates and quality of life.
Monitoring eGFR annually helps track progression. A drop of 5 mL/min/1.73 m² per year signals rapid decline. Interventions such as dietary protein reduction or phosphate binders may be needed.
Understanding what are the levels of kidney disease enables early action. Even mild reductions in kidney function increase long-term health risks. Routine screening identifies issues before symptoms arise.