Healthy kidneys continuously filter the blood.

They remove waste products and excess substances through urine while retaining many substances the body needs.

When kidney function becomes severely impaired, waste products and excess fluid can accumulate.

Advanced kidney failure may eventually require dialysis or kidney transplantation to replace some of the kidneys' essential functions.

But kidney failure usually doesn't appear overnight.

Chronic kidney disease often develops gradually.

A person can lose a substantial amount of kidney function without experiencing obvious symptoms during the early stages.

That's one reason routine medical testing is important for people who have risk factors such as diabetes, high blood pressure, cardiovascular disease, or a family history of kidney disease.

Two commonly used measures are blood creatinine and estimated glomerular filtration rate, or eGFR.

Urine testing can also detect albumin or other abnormalities that may indicate kidney damage.

As CKD progresses, symptoms may eventually include fatigue, swelling, changes in urination, nausea, reduced appetite, itching, sleep problems, or difficulty concentrating.

But symptoms vary, and many can have other causes.

This is why kidney disease cannot be diagnosed from symptoms alone.

There is also an important difference between acute kidney injury and chronic kidney disease.

Acute kidney injury can occur suddenly over hours or days because of severe dehydration, infection, certain medications, obstruction, reduced blood flow to the kidneys, or other causes.

Some people recover substantial kidney function after an acute injury.

Chronic kidney disease, by contrast, involves persistent abnormalities or reduced kidney function over time.

A person who eventually develops end-stage kidney disease may have had years of underlying kidney damage before reaching that stage.

That is why identifying risk factors early matters.

Blood pressure deserves particular attention.

Persistently high blood pressure can damage the small blood vessels within the kidneys. At the same time, damaged kidneys can make blood pressure more difficult to control.

Diabetes is another major concern because prolonged high blood glucose can damage the kidney's filtering structures.

Smoking, cardiovascular disease, obesity, certain medications, and other conditions may also influence kidney health.

None of this means coffee is irrelevant.

Caffeine can temporarily increase blood pressure in some people, especially those who are not accustomed to it.

But that is very different from saying ordinary black coffee directly destroys the kidneys.

The underlying causes of kidney disease are much more complex.

Chapter 3: What Does Science Actually Say About Coffee and the Kidneys?

This is where the viral headline becomes especially misleading.

Research examining coffee and kidney health has not established that ordinary coffee consumption directly causes chronic kidney failure in healthy adults.