Diabetes is the most common cause of chronic kidney disease (CKD), followed closely by high blood pressure. Together, these two conditions account for the majority of CKD cases in the United States, where roughly 35.5 million adults, about 1 in 7, are living with some stage of the disease. About 1 in 3 people with diabetes and 1 in 5 people with high blood pressure develop kidney disease.
How Diabetes Damages the Kidneys
Persistently high blood sugar sets off a chain of damage inside the kidneys’ filtering units, called glomeruli. Excess glucose attaches to proteins and other tissue components through a process called glycation, producing harmful byproducts that accumulate over time. These byproducts trigger inflammation, generate damaging molecules called reactive oxygen species, and cause cells in the kidney’s filters to enlarge and scar. The physical result is a thickening of the membranes inside the filters and an expansion of the tissue between them, both of which progressively reduce the kidney’s ability to clean blood.
High glucose also activates several other damaging pathways inside kidney cells, independent of glycation. The combined effect is a slow, often silent decline in kidney function that can go unnoticed for years. This is why routine screening matters for anyone with type 1 or type 2 diabetes. The earliest sign is usually a small amount of protein leaking into the urine, something you wouldn’t notice on your own but that a simple lab test can detect.
How High Blood Pressure Wears Down Kidney Tissue
Chronic high blood pressure injures the kidneys through a different but equally destructive path. Over time, elevated pressure stiffens and thickens the walls of the small arteries feeding the kidneys. Muscle cells in those artery walls transform into scar-producing cells, migrate inward, and deposit collagen that narrows the vessels. The result is reduced blood flow to the kidney’s filtering units, which begin to shrink and collapse from partial oxygen deprivation.
This oxygen shortage doesn’t stay confined to the filters. It spreads downstream into the surrounding tissue, triggering inflammation and scarring in the spaces between kidney tubules. The tubular cells themselves can shift into a scar-producing state, accelerating the fibrosis. The hallmark of this type of kidney damage is a progressive, widespread scarring of the kidney’s internal architecture. African American individuals tend to develop more severe arterial thickening in the kidneys, which partly explains the higher rates of hypertension-related kidney disease in that population.
What makes the relationship between blood pressure and kidney disease especially tricky is that damaged kidneys also raise blood pressure, creating a cycle where each condition worsens the other.
Other Conditions That Cause CKD
While diabetes and hypertension dominate, several other conditions contribute meaningfully to the overall burden of chronic kidney disease.
Glomerulonephritis refers to a group of diseases that inflame the kidney’s filtering units. The most common form, IgA nephropathy, occurs when a type of immune protein accumulates in the filters, causing gradual damage that can go undetected for years. Autoimmune conditions like lupus can also attack the kidneys directly, as can infections with hepatitis B, hepatitis C, and HIV. These inflammatory kidney diseases collectively represent the third leading cause of kidney failure in the U.S.
Polycystic kidney disease (PKD) is the most common inherited cause. In its dominant form, fluid-filled cysts slowly grow throughout both kidneys, crowding out normal tissue. Symptoms typically appear between ages 30 and 40. PKD accounts for about 5% of all kidney failure cases in the United States, making it the fourth leading cause behind diabetes, hypertension, and glomerulonephritis.
Urinary tract obstruction can also lead to CKD when urine flow is chronically blocked. In men, the most frequent culprit is an enlarged prostate. Kidney stones, tumors, and certain congenital abnormalities can also cause obstruction. When urine backs up, pressure builds in the collecting system, stretching kidney tissue and reducing blood flow. Over time this causes tubular damage and irreversible loss of functional kidney units.
Medications That Can Harm the Kidneys
Drug-induced toxicity accounts for roughly 20% of all kidney injury cases. Common over-the-counter pain relievers like ibuprofen and naproxen (NSAIDs) are among the most frequent offenders, particularly with long-term use. They alter blood flow within the kidney’s filters and can trigger inflammation in the tissue between tubules. Chronic use of other medications, including lithium, certain cancer drugs, and some immune-suppressing drugs used after organ transplants, can also cause slow, progressive kidney damage. If you take any of these regularly, periodic kidney function checks are a reasonable precaution.
How CKD Is Detected and Staged
CKD is diagnosed using two main measurements. The first is an estimated glomerular filtration rate (eGFR), calculated from a blood test that measures how efficiently your kidneys filter waste. Normal is 90 or above. A value between 60 and 89 signals mildly decreased function, 30 to 59 is moderate, 15 to 29 is severe, and below 15 is kidney failure. Importantly, a mildly decreased eGFR alone doesn’t qualify as CKD unless there’s also evidence of kidney damage.
The second measurement is the albumin-to-creatinine ratio (ACR) from a urine sample, which detects protein leaking through damaged filters. Under 30 mg/g is normal, 30 to 300 indicates moderate leakage, and above 300 signals severe leakage. Doctors use both numbers together to classify the stage of disease and estimate the risk of progression. Many people with early-stage CKD have no symptoms at all, which is why screening is so important for anyone with diabetes, high blood pressure, or a family history of kidney disease.
Protecting Your Kidneys
Because diabetes and high blood pressure cause the bulk of CKD, managing these conditions is the most effective form of prevention. For blood sugar, keeping levels in a target range reduces the glycation damage that erodes kidney filters over years. For blood pressure, current guidelines generally recommend treating to below 130/80 mmHg for people at elevated cardiovascular risk, though interestingly, large clinical trials haven’t consistently shown that pushing blood pressure much lower than standard targets provides additional kidney protection beyond what standard treatment achieves.
Beyond managing these two conditions, practical kidney protection includes staying hydrated, limiting long-term NSAID use, maintaining a healthy weight, and not smoking. If you already have early CKD, reducing dietary sodium and moderating protein intake can slow progression. Regular blood and urine tests let you and your doctor catch changes early, when interventions are most effective at preserving the kidney function you still have.