Your kidneys work quietly in the background every minute of every day. They filter waste from your blood, help control fluid levels, regulate electrolytes, contribute to blood-pressure control, and produce hormones involved in red-blood-cell production and bone health.

Because they perform so many essential jobs without attracting much attention, it can be easy to forget about them.

That becomes particularly important when kidney function begins to decline.

Kidney disease can develop gradually, and early chronic kidney disease often causes few or no noticeable symptoms. Some people do not realize there is a problem until routine blood or urine testing reveals an abnormality - or until the disease has become more advanced.

When symptoms do appear, they can be surprisingly subtle. Changes in urination, swelling around the ankles, unusual tiredness, changes in appetite, itchy skin, muscle cramps, or difficulty concentrating can have many explanations. None of these symptoms, by itself, proves that the kidneys are failing.

But when changes are persistent, unexplained, or occur together, they deserve attention.

Understanding these potential warning signs can help you recognize when it may be time to talk with a healthcare professional.

Why Kidney Disease Can Be So Difficult to Detect

The kidneys have considerable functional reserve.

A person can lose some kidney function without immediately noticing a dramatic difference in how they feel.

That is one reason chronic kidney disease can progress silently.

The kidneys may continue performing enough of their essential functions to keep the body relatively stable even as damage develops.

This means that feeling well does not necessarily mean your kidney function is normal.

Early kidney disease is often identified through tests rather than symptoms.

Two particularly important measurements are:

• Estimated glomerular filtration rate (eGFR), which provides an estimate of how well the kidneys are filtering blood.

• Urine albumin-to-creatinine ratio (UACR), which can detect abnormal amounts of albumin leaking into the urine.

These tests can reveal kidney abnormalities before obvious symptoms develop.

1. Changes in How Often You Urinate

One possible change associated with kidney problems is a noticeable change in urination.

You might find yourself urinating:

• More frequently

• Less frequently

• More often during the night

• In larger or smaller amounts than usual

However, changes in urination are not specific to kidney disease.

For example, drinking more fluids, consuming caffeine or alcohol, taking certain medications, having an enlarged prostate, pregnancy, urinary infections, or diabetes can all alter urination patterns.

The important point is not to assume that every change in bathroom habits represents kidney disease.

Instead, persistent or unexplained changes deserve evaluation, particularly if they occur alongside other symptoms.

2. Foamy or Bubbly Urine

Another change worth discussing with a healthcare professional is urine that repeatedly appears unusually foamy or bubbly.

Occasional bubbles are usually not a reason for alarm. Urine can look bubbly simply because of the force with which it enters the toilet or because of cleaning products in the bowl.

Persistent excessive foam can sometimes be associated with protein in the urine.

One important protein is albumin.

Healthy kidneys normally prevent significant amounts of albumin from passing into urine. When the kidney's filtering structures are damaged, albumin can leak through.

This is known as albuminuria.

Importantly, you do not need to wait until you can see foam in your urine to find out whether albumin is present.

A simple urine test can detect albumin more reliably.

3. Blood in the Urine

Blood in the urine, called hematuria, should not simply be ignored.

It can make urine appear pink, red, or brown, although sometimes blood is present in amounts too small to see and is detected only through laboratory testing.

There are many possible causes, including:

• Urinary tract infections

• Kidney stones

• Certain medications

• Prostate problems

• Kidney disease

• Bladder or urinary-tract conditions

Because the causes range from relatively minor to potentially serious, unexplained blood in the urine should be evaluated by a healthcare professional.

It is not something that can safely be attributed to "weak kidneys" without testing.

4. Swelling Around the Feet and Ankles

Swelling is another possible sign of reduced kidney function.

When the kidneys cannot remove enough sodium and fluid, the body may retain additional fluid.

That fluid can accumulate in the lower parts of the body, particularly around the:

• Feet

• Ankles

• Lower legs

Some people notice that shoes feel tighter than usual or that their socks leave deeper marks around the ankles.

However, edema has many possible causes.

Heart disease, liver disease, venous insufficiency, medications, prolonged standing, and other conditions can also cause swelling.