Kidney damage most often results from diabetes and high blood pressure, which together account for the majority of chronic kidney disease (CKD) cases worldwide. As of 2023, about 14.2% of adults globally have some form of CKD, making it far more common than most people realize. The causes range from long-term metabolic conditions to genetics, medications, infections, and environmental exposures.
Diabetes and High Blood Sugar
Persistently elevated blood sugar is the single most common cause of kidney damage. Over time, high glucose levels trigger inflammation throughout the body’s blood vessels, and the kidneys’ tiny filtering units (called glomeruli) are especially vulnerable. Sugar in the bloodstream causes these filters to thicken and scar through three distinct changes: the tissue between capillaries expands, the filtering membrane itself grows thicker, and the capillaries harden. The result is that the kidneys gradually lose their ability to clean your blood.
High blood sugar also activates signaling pathways that increase collagen production inside the kidneys, essentially replacing functional tissue with scar tissue. This process can begin years before you notice any symptoms. Obesity compounds the problem by raising blood pressure through multiple routes, including increased sodium retention and compression of the kidneys themselves. If you have diabetes, your kidneys are working under constant chemical stress, which is why blood sugar management has such a direct impact on kidney health.
High Blood Pressure
Your kidneys contain an intricate network of tiny blood vessels, and they rely on a built-in pressure regulation system to protect themselves. When blood pressure is within a normal range, the small arteries leading into each filtering unit automatically tighten or relax to keep internal pressure steady. But when blood pressure stays elevated for months or years, this protective mechanism gets overwhelmed.
Once pressure inside the glomerular capillaries rises too high, the vessel walls stretch and weaken. Over time, this mechanical stress scars the capillaries and reduces blood flow to kidney tissue. The damage is especially severe when the protective arteries themselves become impaired, because then even moderate blood pressure increases get transmitted directly to the fragile filtering units. Current clinical guidelines recommend keeping systolic blood pressure (the top number) below 120 mmHg for people with CKD, when tolerated, to slow further damage.
High blood pressure and kidney disease form a vicious cycle. Damaged kidneys are worse at regulating blood pressure, which in turn accelerates kidney damage. This is why catching and treating hypertension early matters so much for long-term kidney health.
Immune System Attacks
A group of conditions called glomerulonephritis involves the immune system damaging the kidney’s filtering units. This can happen in several ways. In lupus, the immune system attacks tissues throughout the body, including the kidneys. In a rare condition called Goodpasture’s syndrome, the body produces antibodies that specifically target kidney and lung tissue. Several forms of vasculitis (inflammation of blood vessels) can also cut off blood supply to parts of the kidney.
IgA nephropathy is one of the most common forms. It occurs when a type of antibody that normally fights infections accumulates inside the glomeruli instead. The buildup triggers chronic inflammation that can go undetected for years because it often produces no symptoms until significant damage has occurred.
Infections can also set off immune-mediated kidney damage. Strep throat, for example, can lead to glomerulonephritis one to two weeks after the infection clears, as leftover antibodies lodge in the kidneys. Hepatitis B, hepatitis C, and HIV all cause kidney inflammation through similar immune pathways. In the case of HIV, kidney damage can begin well before the infection progresses to later stages.
Genetic Conditions
Polycystic kidney disease (PKD) is the most well-known inherited cause of kidney failure. In its most common form, autosomal dominant PKD, fluid-filled cysts gradually grow throughout both kidneys, crowding out healthy tissue. About 78% of cases are caused by mutations in the PKD1 gene and another 15% by mutations in PKD2. Although this form has traditionally been considered an adult-onset disease, it can appear across all age groups, from infancy to late adulthood.
A rarer inherited form, autosomal recessive PKD, tends to be more severe and can present in infancy with massively enlarged kidneys, early high blood pressure, and rapid progression toward kidney failure. Researchers have also identified several other genes linked to cystic kidney disease, and genetic variants like APOL1 (more common in people of African descent) are recognized as contributing to CKD risk at a population level.
Medications That Harm the Kidneys
Several common over-the-counter and prescription drugs can cause kidney damage, particularly with long-term or high-dose use. NSAIDs like ibuprofen (Advil, Motrin), naproxen (Aleve), and aspirin at doses above 325 mg per day reduce blood flow to the kidneys. At higher doses and over longer periods, this can lead to acute kidney injury or worsen existing CKD. Even topical NSAID gels are on the list.
Corticosteroids, including prednisone and dexamethasone, stress the kidneys indirectly by causing fluid retention, raising blood pressure, and increasing blood sugar. Many other medications, from certain antidepressants to anti-seizure drugs and opioids, are cleared by the kidneys and can build up to toxic levels if kidney function is already reduced. The risk isn’t always obvious, which is why kidney function testing matters if you take medications regularly.
Obesity and Metabolic Stress
Excess body weight forces the kidneys to filter more blood than they were designed to handle, a state called hyperfiltration. Researchers believe this reflects increased pressure inside the glomerular capillaries, which over time stretches and damages those delicate structures. Animal studies have clearly shown this leads to scarring, and human data supports a similar pattern. Obesity also promotes CKD indirectly by driving diabetes, high blood pressure, and chronic low-grade inflammation.
Environmental Toxins
Cadmium is one of the most studied kidney toxins. Found in cigarette smoke, contaminated food, and certain industrial settings, it accumulates in the kidneys over years. Chronic exposure first damages the kidney’s tubules (the small tubes that reabsorb useful substances from urine), causing protein to leak into the urine. As exposure continues, the glomeruli are damaged too, leading to decreased filtration and, in severe cases, chronic kidney failure. This damage is believed to be irreversible and dose-dependent, meaning the more cadmium exposure over a lifetime, the worse the outcome. Cadmium exposure is also particularly dangerous for people who already have diabetes, as it can accelerate the kidney damage caused by high blood sugar.
Lead, rising global temperatures, and extreme heat exposure are also increasingly recognized as environmental contributors to kidney disease. Heat stress in particular is linked to repeated episodes of dehydration and acute kidney injury, which can accumulate into chronic damage over time.
Sudden Kidney Injury
Not all kidney damage develops slowly. Acute kidney injury (AKI) can happen in days or even hours. The three main triggers are reduced blood flow to the kidneys (from severe dehydration, blood loss, or sepsis), direct damage to kidney tissue (from toxins, medications, or infections), and blockages in the urinary tract that prevent urine from draining. AKI is often reversible if caught quickly, but repeated or severe episodes increase the risk of developing chronic kidney disease later.
How Kidney Damage Is Measured
Kidney function is tracked with two key numbers. The first is your estimated glomerular filtration rate (eGFR), which measures how efficiently your kidneys filter blood. A normal eGFR is 90 or above. A reading of 60 to 89 indicates mildly decreased function, 30 to 44 is moderate to severe, 15 to 29 is severely decreased, and below 15 is kidney failure.
The second number is the albumin-to-creatinine ratio (ACR), which measures how much protein is leaking into your urine. A value under 30 mg/g is normal, 30 to 300 indicates moderate leakage, and above 300 signals severe damage to the filtering units. Together, these two tests give a clear picture of how much kidney function remains and how quickly it may be declining. Most people with early-stage CKD have no symptoms at all, which is why routine blood and urine testing is the only way to catch damage before it becomes irreversible.