Chronic Kidney Disease: Symptoms and Stages — What Does Your eGFR Result Mean?

Chronic kidney disease (CKD) is a progressive, lasting impairment of the kidneys present for at least three months — defined either by a reduced glomerular filtration rate (eGFR below 60 ml/min/1.73 m²) or by the presence of other markers of kidney damage (such as protein in the urine), even when eGFR is normal. It's one of the few serious chronic diseases that can progress for years with essentially no symptoms — the kidneys have substantial functional reserve and can compensate for gradually worsening filtration for a long time before anything becomes noticeable.

According to a 2020 Global Burden of Disease analysis, chronic kidney disease affected hundreds of millions of people worldwide in 2017 and was one of the few leading causes of death whose frequency had been rising rather than falling in recent decades — unlike most other chronic diseases. That divergence has specific causes: an aging population, rising rates of type 2 diabetes and obesity, and the fact that the disease goes undetected for most of its course.

KDIGO (Kidney Disease: Improving Global Outcomes), the organization behind the world's leading nephrology guidelines, classifies CKD along two independent dimensions: eGFR category (G1–G5) and albuminuria category — the amount of protein (albumin) in the urine (A1–A3). This two-dimensional system, known as the CGA classification (Cause, GFR, Albuminuria), predicts the risk of disease progression and cardiovascular complications better than the eGFR result alone.

One often-overlooked detail is worth stressing: categories G1 and G2 alone aren't enough to diagnose CKD unless accompanied by another marker of kidney damage (most often proteinuria, kidney-origin blood in the urine, or structural abnormalities on imaging). A normal eGFR combined with proteinuria still means kidney disease is present — one reason why a creatinine test alone, without an albuminuria assessment, can be insufficient.

Diabetes is the single leading cause of end-stage kidney failure worldwide, and hypertension is the second. According to National Kidney Foundation data, roughly 1 in 3 people with diabetes and 1 in 5 with hypertension have some degree of chronic kidney disease. Both conditions damage the kidneys through different, partly overlapping mechanisms — chronically elevated glucose damages the small blood vessels in the kidneys' filtering units (diabetic nephropathy), while long-standing high blood pressure overloads and gradually destroys the same structures through elevated filtration pressure.

The problem is compounded by the fact that diabetes and hypertension very often coexist in the same person and reinforce each other's effect on the kidneys — while CKD itself, once it develops, further raises blood pressure, closing a vicious cycle. That's why controlling both conditions is simultaneously the most effective known strategy for preventing CKD and the main lever for slowing its progression once it has already developed.

This lag between disease progression and the appearance of symptoms is the key reason screening in at-risk groups — above all people with diabetes, hypertension, and a family history of kidney disease — has a clinical impact disproportionate to how simple and inexpensive it is. The basic screening panel is a blood creatinine test (used to calculate eGFR) and a urine albumin-to-creatinine ratio test (ACR) — both are cheap, widely available, and require no preparation beyond collecting the samples.

Beyond medication, depending on the stage and cause of the disease, a doctor may recommend dietary changes — most often reducing sodium, and in more advanced stages, also controlling protein, potassium, and phosphorus intake. These are decisions that should be individually tailored by a nephrologist or a clinical dietitian specializing in kidney disease, not adopted on your own — excessive, unsupervised protein restriction carries its own risk of malnutrition, especially in older adults.

The decision to start kidney replacement therapy — dialysis (hemodialysis or peritoneal dialysis) or a kidney transplant — isn't made on the eGFR number alone. Stage G5 (eGFR below 15 ml/min/1.73 m²) signals kidney failure and an approaching need for such treatment, but the exact timing of starting dialysis depends on the full clinical picture: the presence of uremic symptoms (including nausea, severe weakness, electrolyte disturbances, or fluid overload resistant to treatment), not the number alone.

In practice, this means some patients with an eGFR only slightly above the G5 threshold already need dialysis because of pronounced symptoms, while others with a lower eGFR but a stable clinical state can be managed conservatively for a while longer under close nephrology follow-up. Preparation for kidney replacement therapy — including choosing a dialysis method and, if possible, transplant evaluation — usually begins already at stage G4, to avoid a sudden, unplanned start of treatment during an acute decline.

Chronic kidney disease belongs to a category of conditions where the biggest difference isn't made by treatment at an advanced stage, but by early detection and consistent control of its causes — above all diabetes and hypertension. Two simple, inexpensive tests — blood creatinine and urine ACR — can catch the problem at a stage where intervention has a real chance of slowing, and sometimes even halting, further progression.