Kidney disease affects roughly 1 in 7 adults worldwide, with a global prevalence of about 14.2% as of 2023. The causes range from common chronic conditions like diabetes and high blood pressure to genetic disorders, infections, medications, and physical blockages in the urinary tract. Most cases develop slowly over years, but some forms of kidney damage strike within hours or days.
Diabetes and High Blood Sugar
Diabetes is the single most common cause of chronic kidney disease. Persistently high blood sugar damages the kidneys through several overlapping mechanisms. First, it forces the kidney’s tiny filters (called glomeruli) to work harder than normal, creating excess pressure inside them. Over time, that pressure wears down the delicate filtering membranes. Second, excess glucose triggers chemical reactions that produce harmful compounds called advanced glycation end products, which promote inflammation and scarring in kidney tissue. Third, and perhaps most concerning, past episodes of high blood sugar can cause lasting changes to how genes are expressed, keeping inflammatory and scarring pathways turned on even after blood sugar improves.
There’s also a feedback loop that makes things worse. When blood sugar stays high, the kidneys ramp up their glucose-reabsorbing machinery to pull sugar back from urine into the bloodstream. This well-intentioned response actually drives blood sugar even higher, accelerating the cycle of damage.
High Blood Pressure
High blood pressure is the second leading cause of kidney disease. The kidneys depend on a dense network of blood vessels to filter waste from your blood. When pressure inside those vessels stays elevated, it gradually damages and narrows them. Less blood reaches the kidney tissue, and the filters lose their ability to do their job. At the same time, damaged kidneys become worse at regulating blood pressure, creating a destructive loop where each condition worsens the other.
Immune System Attacks on the Kidneys
Sometimes the immune system damages the kidneys directly. This group of conditions, broadly called glomerulonephritis, involves inflammation of the kidney’s filtering units. Several autoimmune diseases can trigger it:
- Lupus. A chronic inflammatory disease that can affect the skin, joints, heart, lungs, and kidneys. Up to 5 out of 10 adults with lupus develop kidney involvement. In children with lupus, that number rises to 8 out of 10. Lupus-related kidney disease is typically detected through protein or blood in the urine and confirmed with a kidney biopsy.
- IgA nephropathy. An antibody that normally fights infections begins accumulating inside the kidney filters, causing progressive inflammation and scarring.
- Goodpasture’s syndrome. A rare condition where the immune system creates antibodies that attack tissues in both the lungs and kidneys, potentially causing permanent kidney damage.
Infections That Damage the Kidneys
Certain infections can harm the kidneys either directly or by triggering an immune response that inflames kidney tissue. Strep throat is a classic example. A week or two after a strep infection, antibodies produced to fight the bacteria can accumulate in the kidney filters and cause inflammation. This post-streptococcal glomerulonephritis is more common in children and usually resolves, but it can occasionally lead to lasting damage.
HIV infection poses a more chronic threat. The virus can injure the kidneys directly, and the risk increases substantially when HIV is poorly controlled or when someone also has hepatitis C. Hepatitis C on its own is also linked to kidney disease, making coinfection a particularly dangerous combination.
Genetic Causes
Polycystic kidney disease is the most common inherited kidney disorder. It causes fluid-filled cysts to grow throughout both kidneys, gradually crowding out healthy tissue and impairing function. The dominant form, which requires only one copy of the mutated gene from either parent, affects 1 in 500 to 1,000 people. Symptoms typically appear in adulthood and worsen over decades. The recessive form is far rarer, occurring in roughly 1 in 20,000 to 40,000 people, and tends to cause serious problems in infancy or childhood.
Other inherited conditions, including Alport syndrome and Fabry disease, also affect the kidneys, though they are much less common than polycystic kidney disease.
Medications and Over-the-Counter Painkillers
Common pain relievers can quietly harm the kidneys, especially with heavy or long-term use. NSAIDs (nonsteroidal anti-inflammatory drugs) like ibuprofen and naproxen reduce blood flow to the kidneys, which can trigger acute kidney injury or accelerate existing kidney disease. The risk climbs with higher doses and prolonged use. Even aspirin acts like an NSAID on the kidneys when taken at doses above 325 mg per day.
These aren’t obscure medications. They include widely available brands like Advil, Motrin, and Aleve. If you rely on these regularly for pain management, the cumulative effect on kidney blood flow is worth knowing about, particularly if you already have reduced kidney function or other risk factors.
Urinary Tract Blockages
When urine can’t drain properly, it backs up toward the kidneys and causes them to swell, a condition called hydronephrosis. Left untreated, this swelling can permanently destroy kidney tissue. The most common culprits are kidney stones and an enlarged prostate. Cancers affecting the bladder, prostate, cervix, ovaries, colon, or uterus can also compress or invade the urinary tract and block flow. Unlike most other causes on this list, obstructive kidney disease is often reversible if the blockage is identified and relieved before too much damage accumulates.
Sudden Kidney Injury
Not all kidney disease develops slowly. Acute kidney injury can happen over hours to days, and its causes fall into three broad categories based on where the problem originates.
The first is reduced blood flow to the kidneys. Severe dehydration from vomiting, diarrhea, burns, or blood loss can drop blood volume low enough that the kidneys don’t receive adequate circulation. Sepsis, a life-threatening response to infection, also slashes kidney blood flow by causing blood vessels throughout the body to dilate.
The second is direct damage within the kidneys themselves, from toxins, severe inflammation, or medications.
The third is blockage downstream, where urine can’t exit the body. Kidney stones, blood clots, tumors, or an enlarged prostate can all cause this type of acute injury. In many cases, acute kidney injury is reversible with prompt treatment, but severe or repeated episodes can lead to lasting chronic kidney disease.
How Kidney Disease Is Staged
Doctors measure kidney function using a blood test that estimates your glomerular filtration rate, or GFR, which reflects how efficiently your kidneys filter waste. The scale runs from normal to kidney failure across five stages:
- Stage 1 (GFR 90 or above): Normal filtration rate, but other signs of kidney damage are present, such as protein in the urine.
- Stage 2 (GFR 60 to 89): Mildly decreased function with evidence of damage.
- Stage 3 (GFR 30 to 59): Moderate loss of function, often when symptoms like fatigue or swelling first appear.
- Stage 4 (GFR 15 to 29): Severe reduction, typically requiring planning for dialysis or transplant.
- Stage 5 (GFR below 15): Kidney failure.
Importantly, stages 1 and 2 only count as kidney disease if there is separate evidence of damage, such as protein in the urine or abnormal imaging. A mildly decreased GFR on its own in an older adult does not automatically mean kidney disease. Many people remain in earlier stages for years or even decades, particularly when the underlying cause is managed effectively.