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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.
Fatigue is extremely common, however, and should never automatically be interpreted as kidney disease. Poor sleep, stress, anemia unrelated to kidney function, infections, thyroid problems, nutritional deficiencies and many other conditions can produce similar symptoms. The pattern and persistence of fatigue matter more than a single tired day. Someone experiencing unexplained fatigue that continues despite adequate rest should consider discussing it with a healthcare professional, particularly if other symptoms or kidney-disease risk factors are present.
Another possible sign is swelling, medically known as edema. Healthy kidneys help regulate the amount of sodium and water in the body. When kidney function becomes impaired, excess sodium and fluid can accumulate rather than being removed normally. This can contribute to swelling in the feet, ankles and legs and, in some circumstances, the hands or face. Swelling may become more noticeable later in the day or after prolonged periods of standing, although patterns differ depending on the cause.
Kidney-related swelling can also occur when significant amounts of protein are lost through the urine. Albumin is an important blood protein that helps maintain fluid within blood vessels. Certain kidney diseases damage the filtering structures in ways that allow albumin to escape into the urine. When blood albumin becomes low, fluid may move into surrounding tissues more readily. This can contribute to puffiness around the eyes as well as swelling elsewhere in the body.