Stage 4 kidney disease means your kidneys have moderate to severe damage, with an estimated glomerular filtration rate (eGFR) between 15 and 29. At this level, your kidneys are filtering blood at roughly 15 to 29 percent of normal capacity. No single disease is responsible for every case. The two most common causes are diabetes and high blood pressure, but kidney inflammation, genetic conditions, autoimmune disease, and long-term medication use can all drive kidney function down to this stage.
How Diabetes Damages the Kidneys
Diabetes is the leading cause of chronic kidney disease worldwide. Persistently high blood sugar forces the kidneys to filter more blood than normal, a state called hyperfiltration. Over time, this extra workload damages the tiny blood vessels inside the kidney’s filtering units. The vessels thicken and scar, and the filters begin leaking protein into the urine, a hallmark early warning sign.
High blood sugar also triggers the formation of harmful sugar-protein compounds that accumulate in kidney tissue and provoke inflammation. The combination of these metabolic changes, rising blood pressure, and abnormal cholesterol levels accelerates the scarring process. As more and more filtering units are destroyed, kidney function drops steadily. Without intervention, this progression can take years or even decades, but it reliably moves through the stages of kidney disease toward stage 4 and beyond.
How High Blood Pressure Causes Kidney Scarring
The kidneys have a built-in defense mechanism: small blood vessels at the entrance of each filtering unit can tighten or relax to keep internal pressure stable, even when blood pressure in the rest of the body fluctuates. When blood pressure stays elevated for years, this protective system gradually breaks down. Sustained force pushes through to the delicate filtering capillaries, stretching and damaging them.
The cells that wrap around these capillaries, called podocytes, provide structural support against pressure that is already about twice as high as in capillaries elsewhere in the body (roughly 45 versus 20 mmHg). Podocytes have very limited ability to regenerate. Once they are injured or lost, the filtering unit scars over permanently. This is why uncontrolled high blood pressure can quietly erode kidney function over many years, often without obvious symptoms until the damage is advanced. Diabetes and high blood pressure frequently occur together, and each condition worsens the kidney damage caused by the other.
Kidney Inflammation (Glomerulonephritis)
Several forms of kidney inflammation directly attack the filtering units and can progress to stage 4 disease at very different speeds. Focal segmental glomerulosclerosis (FSGS) is one of the more aggressive forms: about 80 percent of patients progress to kidney failure within 10 years, and a particularly severe variant linked to HIV infection can move faster. Membranoproliferative glomerulonephritis leads to kidney failure in roughly 40 percent of patients over 10 years, while membranous nephropathy does so in 20 to 30 percent.
IgA nephropathy, one of the most common types worldwide, progresses more slowly. About 10 percent of patients reach kidney failure within a decade. At the other extreme, rapidly progressive glomerulonephritis can destroy kidney function in weeks or months, with about 90 percent of patients reaching end-stage disease without aggressive treatment. In all these conditions, the underlying pattern is the same: inflammation triggers scarring in the filtering units, steadily reducing the kidney’s ability to clean the blood.
Polycystic Kidney Disease
Polycystic kidney disease (PKD) is the most common inherited cause of kidney failure. A genetic mutation causes fluid-filled cysts to form inside the kidneys. Over years, these cysts multiply into the hundreds, swelling the kidneys and compressing the delicate internal structures. The growing cysts damage the microscopic blood vessels that filter blood, causing inflammation and permanent scarring.
PKD progresses at different rates depending on the specific genetic mutation involved and other factors like blood pressure control. Some people reach stage 4 in their 40s or 50s, while others maintain better function into later life. Because the damage is structural and cumulative, there is no way to reverse cysts that have already formed, though treatment can slow the rate of growth.
Autoimmune Disease and Lupus
Lupus is the autoimmune condition most closely associated with kidney damage. In lupus nephritis, the immune system attacks the filtering capillaries inside the kidney. The inflammation can range from mild to severe across six classified levels. The most dangerous form, diffuse proliferative glomerulonephritis, causes widespread damage throughout the kidneys and carries a higher risk of progressing to advanced stages.
Overall, about 20 percent of people with lupus nephritis reach kidney failure within 10 years. The critical challenge with autoimmune kidney disease is that inflammation can cause irreversible scarring even when you feel fine. By the time symptoms appear, significant permanent damage may already exist.
Medication-Related Kidney Damage
Certain medications, taken at high doses or over long periods, can cause chronic kidney inflammation that progresses toward stage 4. Common over-the-counter pain relievers, including NSAIDs like ibuprofen and naproxen, are the best-known culprits. Using more than one gram daily for longer than two years, or using them with pre-existing kidney problems, raises the risk of chronic damage that can advance to kidney failure.
NSAIDs harm the kidneys in part by interfering with the blood flow regulation that protects the filtering units from pressure damage. Lithium, used for mood disorders, can also cause chronic kidney inflammation and scarring with long-term use. Even acetaminophen and aspirin carry risk when used chronically at high doses. The damage from these medications is often gradual and silent, making it easy to miss until kidney function has already declined substantially.
What Stage 4 Feels Like
Earlier stages of kidney disease are often symptom-free. By stage 4, waste products begin building up in the blood faster than the kidneys can remove them. Nausea, vomiting, and loss of appetite are typically the first things people notice. A metallic taste in the mouth, persistent fatigue, muscle cramps, and itchy skin are also common. Some people experience difficulty concentrating or remembering things clearly, caused by toxin buildup affecting brain function.
Swelling in the ankles, hands, or face can develop as the kidneys lose the ability to manage fluid balance. Shortness of breath may follow, either from fluid overload or from anemia. By stage 4, the kidneys also struggle to produce enough of the hormone that stimulates red blood cell production, and anemia becomes increasingly common. Almost half of people with moderately reduced kidney function already have anemia, and the proportion rises sharply as function declines further.
Electrolyte imbalances also emerge at this stage. Potassium and phosphorus levels can rise to problematic levels, and disrupted calcium and phosphorus balance begins weakening bones. These complications develop because the kidneys handle far more than just waste removal: they regulate blood chemistry, blood pressure, red blood cell production, and bone health. When filtering capacity drops below 30 percent, all of these systems start to struggle.
Why Multiple Causes Often Overlap
In practice, most people who reach stage 4 have more than one factor driving the damage. Someone with diabetes typically also develops high blood pressure, and the two conditions reinforce each other’s effects on kidney tissue. A person with mild genetic kidney disease who takes NSAIDs regularly may progress faster than either risk factor would predict alone. Once kidney function drops below a certain threshold, the remaining healthy tissue faces increased workload, which itself causes further damage, creating a cycle of decline even if the original cause is controlled. This is why identifying and managing all contributing factors, not just the primary diagnosis, matters so much in slowing progression at stage 4.