What Causes Low Kidney Function Key Risk Factors?

Kidney function declines when the kidneys lose some of their filtering capacity. The most common causes are diabetes and high blood pressure, which together account for a large share of chronic kidney disease cases in the United States. Other risk factors include age, family history, heart disease, obesity, smoking, and long-term use of certain medications. Many people with reduced kidney function have no symptoms until the decline is advanced, which is why testing matters more than how you feel.

Your kidneys filter about 150 quarts of blood every day. They remove waste, balance fluids and electrolytes, and help control blood pressure. When that filtering slows, waste builds up quietly. Understanding what drives the decline is the first step toward protecting the kidneys you have.

What Causes Low Kidney Function Key Risk Factors?

Diabetes and high blood pressure are the two leading causes of chronic kidney disease. High blood sugar damages the tiny blood vessels and filters inside the kidneys. High blood pressure does damage in a different way: it pushes blood through those delicate filters with too much force, and over years that pressure scars them.

This is where a common misunderstanding matters. Many people assume kidney problems come from something they did wrong. In most cases, the damage is the downstream result of a condition that was already present, often for years, sometimes without symptoms. That is why managing blood sugar and blood pressure is the central strategy for protecting kidney function.

Beyond those two, several other conditions and circumstances raise risk:

• Diabetes — the leading cause of kidney failure in the U.S.
• High blood pressure — the second leading cause
• Heart disease — shares many risk factors and often coexists with kidney disease
• Family history of kidney failure — genetics play a real role
• Obesity — increases strain on the kidneys and raises diabetes and hypertension risk
• Smoking — damages blood vessels throughout the body, including the kidneys
• Age — kidney function declines gradually with age in most people
• Certain medications — some long-term use can harm the kidneys
• Acute kidney injury — a past sudden injury to the kidneys raises future risk

Each of these contributes in a different way. Some are modifiable. Some are not. Knowing which apply to you is more useful than knowing which are most common.

How Does Diabetes Damage the Kidneys?

Persistently high blood glucose damages the glomeruli — the tiny filtering units inside each kidney. Over time, the damage causes these filters to leak protein that should stay in the blood and to lose their ability to filter waste efficiently.

The process is slow and largely silent. In the early stages, the kidneys may actually filter faster than normal, which masks the damage. A urine test that detects small amounts of protein — called albumin — is often the first sign something is wrong. That is why guidelines recommend regular kidney screening for people with diabetes, even when they feel fine.

Tight control of blood sugar is the single most effective way to slow kidney damage in people with diabetes. Research consistently shows that better glucose control reduces the risk of kidney complications. Blood pressure control matters just as much, because the two conditions compound each other.

How Does High Blood Pressure Harm the Kidneys?

High blood pressure damages the small blood vessels in the kidneys. The kidneys depend on a dense network of tiny vessels to filter blood. When pressure stays elevated, those vessels thicken and stiffen, and the filtering units lose efficiency.

There is a feedback loop here that makes the problem worse. Damaged kidneys are less able to regulate blood pressure, so blood pressure tends to rise further. That additional pressure causes more kidney damage, which raises blood pressure again. Breaking that cycle with treatment is one of the most important things a person can do.

Blood pressure below 120/80 mmHg is considered normal. For people with kidney disease, clinicians often aim for tighter control than for the general population, though the exact target is individualized. Your clinician can set a target based on your specific situation.

What Role Does Age Play in Kidney Function?

Kidney function declines naturally with age in most people. The glomerular filtration rate — the standard measure of how well the kidneys filter — typically falls gradually after about age 40. This is a normal part of aging, not a disease.

The distinction matters. A modest decline in an older adult with no other risk factors may not require treatment, just monitoring. But age also raises the risk of the conditions that cause kidney disease: diabetes, high blood pressure, and heart disease all become more common with age. So age is both a direct factor and an indirect one.

Kidney function is measured with a blood test that estimates the glomerular filtration rate, often abbreviated eGFR. A value of 60 or above is generally considered normal in adults without other signs of kidney damage. A value below 60 for three months or more is one criterion for chronic kidney disease. Age affects how that number is interpreted, which is why clinicians look at the whole picture rather than a single result.

Which Medications and Substances Can Harm the Kidneys?

Some medications can damage the kidneys, especially with long-term use or in people whose kidney function is already reduced. The most commonly discussed are nonsteroidal anti-inflammatory drugs, or NSAIDs — a category that includes ibuprofen and naproxen. Occasional use is generally considered safe for most healthy adults, but regular long-term use carries risk, particularly in people with existing kidney disease or those taking other medications that affect the kidneys.

Other substances that can stress the kidneys include certain contrast dyes used in imaging, some antibiotics, and lithium. Dehydration makes all of these risks worse, because the kidneys have less fluid to work with.

This does not mean these medications should be avoided entirely. It means the risk depends on dose, duration, and your individual situation. Anyone with reduced kidney function should tell their clinician about all medications and supplements they take, including over-the-counter drugs. Some herbal supplements have been linked to kidney damage, and the FDA does not review supplements for safety before they are sold.

What Other Conditions and Factors Raise Kidney Disease Risk?

Several conditions beyond diabetes and high blood pressure can affect kidney function. Glomerulonephritis is a group of diseases that cause inflammation of the kidney filters. Polycystic kidney disease is an inherited condition that causes cysts to grow in the kidneys. Lupus and other autoimmune conditions can also involve the kidneys.

Acute kidney injury is another important factor. This is a sudden loss of kidney function, often from severe dehydration, infection, surgery, or certain medications. Many people recover fully, but a past episode raises the risk of chronic kidney disease later.

Race and ethnicity matter here, but not in the way many people assume. Black Americans experience kidney failure at higher rates than white Americans. Much of this difference is tied to higher rates of diabetes and high blood pressure, along with differences in access to care. Some of it is genetic. A variant in the APOL1 gene, which is more common in people of West African ancestry, is associated with higher risk of certain kidney diseases. Researchers are still working out how to use that information in practice.

Can You Prevent Low Kidney Function?

You cannot prevent every cause of kidney disease. You can lower your risk substantially by managing the conditions that drive it. Blood sugar control, blood pressure control, and avoiding smoking are the three with the strongest evidence behind them.

Regular testing is the other half of the strategy. A simple blood test for eGFR and a urine test for protein can detect kidney disease early, when treatment is most effective. People with diabetes, high blood pressure, heart disease, or a family history of kidney failure should ask their clinician how often they should be tested. The answer depends on individual risk.

No supplement or diet has been shown to reverse kidney damage. Some dietary patterns — particularly reducing sodium and eating less processed food — support blood pressure control and reduce strain on the kidneys. Anyone with reduced kidney function should talk to their clinician before making major dietary changes, especially around protein, potassium, and phosphorus, because the right approach depends on the stage of disease.