Some people with advanced kidney disease report a metallic, bitter, or otherwise unpleasant taste.
When kidney function becomes severely reduced, waste products can accumulate in the blood. These changes may affect taste and appetite. Some people also experience bad breath or a sensation that food tastes different.
The result can be a cycle: food becomes less appealing, appetite decreases, and nutritional intake falls.
Dental problems, gum disease, sinus infections, reflux, medications, and oral dryness can also change taste. A persistent metallic taste is therefore not a reliable kidney test.
If it appears together with other symptoms, it should be mentioned during a medical consultation.
15. Difficulty concentrating or unusual mental fog
The brain depends on a stable internal environment. Severe disturbances in fluid, electrolyte, and waste-product balance can affect how the nervous system functions.
People with advanced kidney disease may experience difficulty concentrating, reduced alertness, memory problems, or a feeling of mental fog.
Sleep disruption and anemia may contribute as well.
However, concentration problems are common in people experiencing stress, anxiety, depression, sleep deprivation, medication effects, or other health conditions.
Sudden confusion, severe drowsiness, or a rapid change in mental state is different from ordinary forgetfulness. It can signal a medical emergency and requires immediate attention.
16. Headaches or a feeling of pressure
The kidneys play an important role in blood pressure regulation. They help control the amount of salt and water in the body and participate in hormonal systems that influence blood vessel tone.
When kidney function is impaired, blood pressure may become difficult to control. High blood pressure can also damage the kidneys, creating a cycle in which each condition makes the other worse.
Some people with very high blood pressure experience headaches, although high blood pressure often causes no obvious symptoms at all.
A headache by itself is not a dependable sign of kidney disease. It may be related to tension, migraine, dehydration, infection, or many other causes.
Checking blood pressure is far more informative than trying to diagnose kidney problems from the location or intensity of a headache.
17. Shortness of breath during ordinary activities
Breathlessness can occur in advanced kidney disease for several reasons.
When the kidneys cannot remove enough fluid, excess fluid may accumulate in the body. In serious cases, fluid can build up in the lungs and make breathing difficult.
Anemia can also reduce the blood's ability to carry oxygen, making physical activity feel more exhausting.
Some people notice breathlessness when climbing stairs, walking short distances, or lying flat. Others may experience it even while resting.
This symptom must never be dismissed as a routine sign of aging. Heart and lung conditions, blood clots, infections, and other medical problems can also cause breathlessness.
Severe or sudden breathing difficulty, chest pressure, or blue or grey lips requires emergency medical attention.
18. Trouble sleeping or waking repeatedly at night
Sleep problems may accompany chronic kidney disease, particularly in more advanced stages.
Some people wake frequently because they need to urinate. Others experience itching, muscle cramps, restless legs, discomfort, or difficulty settling down.
Poor sleep can then worsen fatigue and concentration problems during the day.
It is important not to assume that insomnia means kidney damage. Stress, irregular schedules, sleep apnea, caffeine, depression, and many other factors can disrupt sleep.
However, if sleep difficulties appear alongside swelling, persistent itching, or noticeable urinary changes, they are worth mentioning to a healthcare professional.
19. Numbness or tingling in the hands and feet
A sensation of pins and needles, reduced feeling, or unusual numbness can occur for many reasons.
In advanced kidney disease, disturbances in mineral balance and other metabolic changes may affect nerves. Some people experience tingling, weakness, or altered sensation in their hands and feet.
Kidney disease can also coexist with diabetes, which is itself a major cause of peripheral nerve damage. In such cases, the symptoms may be related to diabetes, kidney disease, or both.
Numbness is not a specific kidney warning. Vitamin deficiencies, nerve compression, circulation problems, and neurological conditions are also possible causes.
Sudden numbness affecting one side of the body, especially with facial weakness or difficulty speaking, requires emergency assessment because it may indicate a stroke.
20. High blood pressure that is difficult to control
High blood pressure is both a major risk factor for kidney disease and a possible consequence of declining kidney function.
The kidneys regulate blood volume and release substances that influence blood vessel activity. When kidney function is impaired, the body may retain more salt and water, contributing to increased blood pressure.
Over time, uncontrolled high blood pressure can damage the delicate blood vessels inside the kidneys. This can reduce their filtering ability and worsen existing disease.
Many people with high blood pressure feel perfectly normal. That is why regular measurement is essential, even when there are no headaches or other symptoms.
People who need several medications to control their blood pressure, or whose readings remain consistently high, should discuss whether kidney testing is appropriate.
21. Changes in skin color or unusual darkening
The illustration includes a person with several red patches on the back. This is a striking image, but it should not be interpreted as a typical visual signature of kidney failure.
Some people with advanced kidney disease develop changes in skin appearance, including dryness, dullness, or darker areas. Metabolic changes, inflammation, scratching, and other factors may contribute.
However, red spots, bruises, widespread discoloration, or sudden skin changes can have many different causes. Some may be related to allergies, infections, medication reactions, blood vessel conditions, or other illnesses.
A person should not use skin color as a home test of kidney function. A new, spreading, painful, blistering, or unexplained rash deserves medical assessment, particularly if it is accompanied by fever or other symptoms.
22. Pain or discomfort around the back and sides
The picture shows a person holding the lower back, with a red area suggesting pain around the kidney region.
The kidneys are located toward the back of the upper abdomen, beneath the lower ribs. Pain caused by kidney-related conditions may be felt in the side or flank rather than directly in the center of the lower back.
Kidney stones, infections, obstruction, and certain inflammatory conditions can cause pain in this area. Depending on the cause, discomfort may be sharp, severe, persistent, or accompanied by fever, nausea, or urinary symptoms.
But ordinary lower-back pain is much more commonly associated with muscles, joints, discs, posture, or physical strain. Most back pain does not mean that the kidneys are failing.
A person should seek medical advice for severe flank pain, pain with fever, blood in the urine, vomiting, or difficulty passing urine. Sudden severe pain should not be self-diagnosed from a picture.
23. Feeling unusually weak or unable to manage normal activities
The final warning sign is a general decline in strength and everyday functioning.
People with advanced kidney disease may experience a combination of anemia, waste accumulation, poor appetite, sleep disturbance, muscle cramps, and changes in electrolyte balance. Together, these problems can make ordinary activities feel unusually demanding.