Kidney damage most often results from diabetes or high blood pressure, which together account for the majority of chronic kidney disease cases. But dozens of other causes exist, from medications you might take regularly to infections, genetic conditions, and physical blockages in the urinary tract. About 14% of U.S. adults have some degree of chronic kidney disease, and many don’t know it because early damage produces no symptoms.
Your kidneys filter roughly 50 gallons of blood per day through tiny clusters of blood vessels called glomeruli. Anything that damages these filters, cuts off blood supply, or blocks urine outflow can cause kidney damage, either suddenly or over years.
Diabetes: The Leading Cause
Persistently high blood sugar is the single most common cause of kidney damage. Among people with chronic kidney disease, about 36% also have diabetes. The damage isn’t just about sugar levels being too high; it’s about what that sugar does to the kidney’s internal structures over time.
When blood sugar stays elevated, it triggers a cascade of harmful changes inside the kidney. The filtering units are forced to work harder than normal, a state called hyperfiltration. Think of it like running a pump at maximum pressure all the time. This overwork causes the delicate membranes inside those filters to thicken and stiffen. Meanwhile, high glucose generates harmful molecules that increase inflammation, promote scarring (fibrosis), and damage the specialized cells (podocytes) that form the kidney’s filtration barrier. These podocytes can shrink, thin out, and eventually die.
The three hallmark changes in diabetic kidney damage are expansion of the tissue between filtering blood vessels, thickening of the filter membrane itself, and hardening of the small arteries feeding the kidney. This process typically unfolds over years, which is why people with diabetes are advised to have their kidney function tested regularly. By the time symptoms appear, significant damage has usually occurred.
High Blood Pressure and Blood Vessel Damage
Your kidneys depend on a network of tiny arteries to deliver blood for filtering. High blood pressure gradually damages those vessels from the inside. Initially, the kidneys can adjust to moderate pressure increases through a built-in self-regulating mechanism. But when blood pressure climbs too high or stays elevated for too long, that protective system fails.
Once pressure exceeds what the kidneys can compensate for, it pushes directly into the glomerular capillaries. The walls of the small renal arteries thicken and stiffen in response, narrowing the space blood can flow through. This creates a vicious cycle: the kidneys receive less blood, which paradoxically triggers the body to raise blood pressure further, which accelerates the damage. Over time, reduced blood flow starves kidney tissue and leads to permanent scarring. Rising rates of obesity and hypertension in the general population have made this an increasingly important driver of kidney disease.
Immune System Attacks on the Kidney
A group of conditions collectively called glomerulonephritis occurs when the immune system mistakenly targets the kidney’s filtering units. These are among the more serious causes of kidney damage because they can progress quickly if untreated.
In some forms, the immune system attacks proteins found only in the kidney. In anti-GBM disease, for example, antibodies target a specific component of the filter’s basement membrane. In other forms, the immune attack is part of a body-wide autoimmune condition. Lupus nephritis occurs when antibodies that target the body’s own DNA deposit in the kidneys. IgA nephropathy, the most common form of glomerulonephritis worldwide, involves abnormal antibodies that accumulate in the kidney’s filters and provoke inflammation.
Other immune-mediated kidney diseases include conditions where antibodies attack the blood vessels supplying the kidneys (ANCA vasculitis) and those where the complement system, a branch of immune defense, goes into overdrive and damages kidney tissue directly. Each type involves a different immune pathway, which is why treatment approaches vary significantly.
Medications That Harm the Kidneys
Several common medications can damage kidney tissue, especially with prolonged use or in people whose kidneys are already vulnerable. The most widely used culprits are over-the-counter pain relievers like ibuprofen and naproxen. These drugs reduce blood flow to the kidneys and can cause both acute injury and chronic damage with long-term use. They can also trigger inflammation in the kidney’s inner tissue.
Prescription medications pose risks too. Certain antibiotics are directly toxic to the tubular cells that line the kidney’s internal plumbing. Some antiviral drugs can form crystals that physically block the tiny tubes inside the kidney. Immunosuppressant drugs used after organ transplants and lithium, used for mood disorders, can cause slow, progressive kidney scarring over years. Even blood pressure medications that are generally protective of kidneys can temporarily reduce filtering capacity, particularly when someone is dehydrated or taking multiple drugs that affect kidney blood flow.
Sudden Kidney Injury
Not all kidney damage develops slowly. Acute kidney injury can happen over hours or days and has three broad categories of causes: reduced blood flow, direct damage to the kidneys, or physical blockage of urine outflow.
Reduced blood flow is the most common trigger. Severe dehydration, major blood loss, and sepsis (a life-threatening infection response) can all starve the kidneys of the blood they need to function. Heart failure and liver failure can have the same effect by redirecting blood flow away from the kidneys.
Direct damage can come from toxins, medications, or severe infections that attack kidney cells. Blockage of urine outflow, whether from kidney stones, an enlarged prostate, or tumors pressing on the ureters (the tubes connecting kidneys to the bladder), creates backpressure that damages kidney tissue. When urine can’t drain, it essentially backs up into the kidney itself, and if the blockage isn’t relieved, the damage becomes permanent.
Genetic Conditions
Polycystic kidney disease is the most common inherited cause of kidney damage. It results from mutations in genes that produce proteins called polycystin-1 and polycystin-2, which help regulate cell growth in the kidneys. When these proteins don’t work correctly, fluid-filled cysts form and gradually enlarge throughout both kidneys over the patient’s lifetime.
The cysts crowd out and compress normal kidney tissue, and the kidneys can grow to several times their normal size. A characteristic feature of this disease is that kidney function, as measured by standard blood tests, can appear relatively stable for decades before declining sharply. Patients typically experience a significant drop in function only 10 to 15 years before reaching the point where dialysis or transplant becomes necessary, making monitoring essential even when results look reassuring.
Environmental Toxins
Long-term exposure to certain heavy metals is a well-established cause of kidney damage. Arsenic, cadmium, and lead are the most thoroughly documented. Cadmium is particularly damaging to the proximal tubules, the section of the kidney responsible for reabsorbing essential nutrients and filtering waste from the blood. Exposure sources include contaminated water, certain occupations (mining, battery manufacturing, welding), and even tobacco smoke, which concentrates cadmium.
Lead exposure, while less common now than in previous decades, still affects populations living in older housing with lead paint or lead plumbing. These metals accumulate in the body over time, so even low-level chronic exposure can eventually cause measurable kidney damage.
Urinary Tract Obstruction
Any blockage that prevents urine from draining out of the kidneys can cause damage through backpressure. Kidney stones are a common culprit, particularly when they lodge in a ureter. An enlarged prostate can compress the urethra or bladder outlet, indirectly causing pressure to build upstream. Tumors, both cancerous and noncancerous, can press on the ureters from outside.
A rarer cause is retroperitoneal fibrosis, where fibrous tissue grows behind the abdomen and gradually encircles and squeezes the ureters shut. This can develop in connection with certain cancers or as a side effect of some migraine medications. Regardless of the cause, the principle is the same: when urine backs up into the kidneys, the resulting pressure damages the delicate internal structures. If the obstruction is caught early and relieved, kidney function can often recover. Left untreated, the damage becomes irreversible.
How Kidney Damage Is Measured
Kidney function is tracked using two key measurements. The first is the glomerular filtration rate (GFR), estimated through a blood test. A GFR above 90 is considered normal. Between 60 and 89 indicates mildly reduced function. Below 60, the kidneys are working at less than two-thirds capacity, and below 15 is classified as kidney failure, the stage where dialysis or transplant is typically needed.
The second measurement is the amount of protein leaking into your urine. Healthy kidneys keep protein in the blood, so finding it in urine signals filter damage. A urine albumin level between 30 and 300 mg/g (sometimes called moderately increased albuminuria) is an early warning sign. Both measurements together give a more complete picture than either one alone, which is why kidney screening typically involves both a blood draw and a urine sample.