The kidneys perform several essential jobs every hour of the day, usually without producing any sensation that people can notice. They filter the blood, remove waste products and excess fluid, help regulate minerals such as sodium and potassium, and contribute to blood-pressure control. The kidneys also produce hormones involved in red blood cell production and bone  health. Because these organs affect so many systems, reduced kidney function can eventually produce symptoms in different parts of the body.

However, symptoms alone cannot determine whether someone has kidney disease, and many people with early chronic kidney disease have no symptoms at all. That last point is particularly important because kidney disease is sometimes described online as something that can easily be identified from a list of warning signs. In reality, chronic kidney disease often develops gradually and may remain unnoticed until it becomes more advanced. A person can feel completely well while blood or urine testing already shows abnormalities.

Conversely, someone may experience fatigue, swelling or urinary changes for reasons unrelated to the kidneys. The purpose of recognizing possible symptoms is therefore not to diagnose yourself but to know when medical evaluation may be appropriate. Doctors commonly evaluate kidney health with blood and urine tests. A blood test can be used to estimate glomerular filtration rate, usually called eGFR, which provides information about how effectively the kidneys are filtering blood.

A urine albumin-to-creatinine ratio, or uACR, can detect excess albumin in the urine, which may indicate kidney damage. These tests are particularly important for people with risk factors such as diabetes, high blood pressure, heart disease or a family history of kidney failure. Early detection can provide an opportunity to address causes and slow further damage. One possible symptom of more advanced kidney disease is persistent fatigue or weakness.

Healthy kidneys produce erythropoietin, commonly called EPO, a hormone that helps signal the bone marrow to produce red blood cells. When kidney function declines significantly, EPO production may decrease and anemia can develop. Anemia means the blood has reduced capacity to carry oxygen effectively to tissues. This can contribute to tiredness, weakness, difficulty concentrating and reduced exercise tolerance. Kidney disease can also cause fatigue through other mechanisms, including accumulation of waste products and disrupted sleep.