Kidney disease develops when something damages the kidneys’ filtering units, reducing their ability to clean waste from your blood. The two most common causes are diabetes and high blood pressure, which together account for the majority of cases. But the full list of causes is longer than most people realize, ranging from genetics and infections to medications you might take regularly. Globally, about 788 million adults have some form of chronic kidney disease, with an overall prevalence of roughly 14%.
Diabetes and High Blood Sugar
Diabetes is the single leading cause of kidney disease worldwide. When blood sugar stays elevated over months and years, it triggers a cascade of chemical reactions inside the kidneys’ tiny filtering clusters, called glomeruli. Excess glucose gets converted into compounds that generate harmful molecules called free radicals, while also depleting the kidney cells’ natural antioxidant defenses. At the same time, high blood sugar activates pathways that stimulate scarring and thickening of the tissue surrounding those filters.
The damage follows a predictable pattern. First, the membrane that acts as the kidney’s sieve begins to thicken. Then the supportive tissue around each filter expands, crowding out healthy structures. Over time, nodules of scar tissue form, and the filters harden. The earliest clinical sign is protein leaking into the urine, something healthy kidneys normally prevent. Left unmanaged, diabetic kidney disease can progress through increasingly severe stages until the kidneys lose their filtering ability entirely.
High Blood Pressure
Chronic high blood pressure is the second most common cause of kidney disease. Your kidneys contain a vast network of tiny blood vessels, and sustained high pressure physically damages their walls. The vessel walls thicken and stiffen as smooth muscle cells multiply and plasma proteins seep into the tissue. This process, called nephrosclerosis, gradually narrows the vessels that supply blood to the kidney’s filters.
As blood flow to the filtering units drops, they lose function one by one. The kidneys also play a role in regulating blood pressure, so the relationship becomes a vicious cycle: damaged kidneys struggle to control blood pressure, which accelerates further damage. Keeping blood pressure within a healthy range is one of the most effective ways to protect kidney function, whether or not you already have early-stage disease.
Genetic Conditions
Some people are born with genes that make kidney disease inevitable without intervention. Polycystic kidney disease (PKD) is the most well-known inherited form. In the autosomal dominant type, mutations in one of two genes (PKD1 or PKD2) cause thousands of fluid-filled cysts to grow throughout both kidneys. These genes normally produce proteins that help kidney cells develop and organize properly. When the proteins malfunction, cells multiply abnormally and form cysts that gradually replace healthy tissue.
PKD1 mutations cause the more common and typically more severe form, while PKD2 mutations tend to progress more slowly. A rarer autosomal recessive form, caused by mutations in a different gene (PKHD1), appears in infancy or childhood and is often more aggressive. As cysts enlarge over decades, they crowd out working kidney tissue and can eventually lead to kidney failure.
Autoimmune Diseases
In autoimmune kidney disease, your immune system mistakenly attacks your own kidney tissue. Lupus nephritis is one of the most serious examples. The immune system produces antibodies that form clumps called immune complexes, which get trapped in the kidney’s filters. Once lodged there, these complexes activate the body’s inflammatory response, attracting white blood cells that cause swelling, tissue destruction, and scarring. In some lupus patients, antibodies also trigger blood clots within the kidney’s tiny vessels, further reducing blood flow.
IgA nephropathy works through a similar but distinct mechanism: a specific type of antibody (IgA) deposits in the kidney filters and triggers inflammation over time. These conditions can smolder for years before symptoms appear, which is why routine urine and blood tests matter for anyone with a known autoimmune condition.
Medications and Painkillers
Long-term use of common over-the-counter painkillers can quietly damage the kidneys. NSAIDs like ibuprofen and naproxen, as well as aspirin, can harm the small filtering blood vessels inside the kidney when taken regularly over months or years. This condition, called analgesic nephropathy, can progress to acute kidney failure and, in later stages, has been linked to kidney cancer and hardening of the kidney’s arteries.
Prescription medications can also cause problems. Certain antibiotics, antiviral drugs, chemotherapy agents, and even proton pump inhibitors (used for acid reflux) can inflame the tissue between the kidney’s filtering units. Contrast dyes used in CT scans and other imaging procedures are another well-known cause of sudden kidney injury, particularly in people whose kidneys are already compromised.
Obesity and Excess Body Weight
Carrying significant excess weight forces your kidneys to work harder. Your kidneys adjust their filtration rate based on your body’s metabolic demands, and a larger body produces more waste that needs clearing. Research comparing obese and lean individuals found that people with a BMI of 30 or higher had a three-fold higher rate of glomerular hyperfiltration (27% versus 7%). This hyperfiltration creates elevated pressure inside the kidney’s delicate capillaries, which over time damages the filtering membranes and leads to protein leaking into the urine.
Obesity also raises the risk of diabetes and high blood pressure, compounding the kidney threat from multiple directions simultaneously.
Urinary Tract Obstructions
When urine can’t drain properly, it backs up into the kidneys and causes swelling, a condition called hydronephrosis. The most common culprits are kidney stones and, in older men, an enlarged prostate. Stones can physically block the tube connecting the kidney to the bladder, while a very enlarged prostate can prevent the bladder from emptying, causing urine to back up into the kidneys.
Short-term blockages usually resolve without permanent harm. But chronic or severe obstruction causes the kidney’s internal structures to stretch and scar. Without treatment, a severely swollen kidney can lose its ability to filter blood entirely. Other causes of obstruction include tumors pressing on the urinary tract and, less commonly, retroperitoneal fibrosis (scarring of the tissue behind the abdomen).
Infections
Recurring or persistent kidney infections (pyelonephritis) can cause permanent scarring. Each time bacteria invade the kidney, the resulting inflammation heals by forming scar tissue. Over repeated episodes, these scars accumulate and destroy functional kidney tissue. This process is especially damaging in people who have vesicoureteral reflux, a condition where urine flows backward from the bladder into the kidneys, carrying bacteria with it.
The scarring from chronic pyelonephritis is progressive. In severe cases, it can advance to end-stage kidney disease requiring dialysis or transplant. Bacterial virulence factors, meaning certain strains being more aggressive than others, also influence how much damage each infection causes.
Environmental Toxins and Heavy Metals
Chronic exposure to certain heavy metals directly poisons the kidney’s tubular cells, which are responsible for reabsorbing useful substances and excreting waste. Lead accumulates in these cells over years or decades of exposure. Short-term lead exposure causes the tubules to malfunction, leading to excess uric acid in the blood (which can cause gout), sugar in the urine, and amino acid loss. Chronic exposure over 5 to 30 years causes the tubules to atrophy and surrounding tissue to scar, eventually impairing kidney function and raising blood pressure.
Cadmium, found in cigarette smoke, certain industrial settings, and contaminated food, causes similar tubular dysfunction. Early signs include small proteins and sugar appearing in the urine, indicators that the tubules have lost their ability to properly reclaim filtered substances.
Sudden Versus Chronic Kidney Injury
Not all kidney disease develops slowly. Acute kidney injury (AKI) can strike within hours or days, and about 70% of cases that develop outside the hospital stem from reduced blood flow to the kidneys rather than direct kidney damage. Severe dehydration from vomiting or diarrhea, heart failure, and sepsis can all slash blood flow enough to impair filtration rapidly.
Direct kidney damage from toxins, prolonged low blood pressure, or an inflammatory reaction to medications accounts for most of the remaining cases. Postrenal causes, where something blocks urine from leaving the body, are less common but important to identify because they’re often reversible. In older men, an enlarged prostate is the most frequent postrenal cause.
Acute kidney injury sometimes resolves completely, but severe or repeated episodes can leave lasting damage that transitions into chronic kidney disease.
How Kidney Disease Is Measured
Kidney disease is staged based on two measurements: how well your kidneys filter blood (measured by GFR, or glomerular filtration rate) and how much protein leaks into your urine. A GFR of 90 or above is normal. Between 60 and 89 is mildly decreased, 30 to 59 is moderate, 15 to 29 is severe, and below 15 is classified as kidney failure. Importantly, a mildly decreased GFR alone doesn’t qualify as kidney disease unless there’s also evidence of damage, such as protein in the urine or structural abnormalities on imaging.
Protein in the urine is graded separately. A urine albumin-to-creatinine ratio under 30 is normal, 30 to 300 indicates moderate protein loss, and above 300 signals severe leakage. Your specific combination of GFR category and protein level determines both the stage of disease and how aggressively it needs to be monitored.