One of the challenges of kidney disease is that the body can compensate for a gradual loss of kidney function. In its early stages, chronic kidney disease may cause no noticeable symptoms at all.
When symptoms do appear, they can be vague. Some people experience fatigue, reduced appetite, swelling in the feet or ankles, changes in urination, or difficulty concentrating. Others may notice foamy urine, which can sometimes indicate excess protein in the urine, although it can also occur for other reasons.
These symptoms are not specific to kidney disease. Fatigue, for example, can result from anemia, poor sleep, infection, or many other conditions. Likewise, changes in urine appearance do not automatically mean the kidneys are damaged.
That is why testing is often more reliable than relying on how a person feels. Two common assessments are a blood test measuring creatinine, which can be used to estimate the glomerular filtration rate (eGFR), and a urine test measuring the albumin-to-creatinine ratio (uACR). The first helps assess filtration, while the second can detect a type of protein leakage associated with kidney damage.
A single abnormal result does not always establish chronic kidney disease. Clinicians may repeat tests and consider the person's medical history, medications, and other findings. Chronic kidney disease is generally identified when abnormalities persist for at least three months or other evidence establishes chronic damage.
People with diabetes, high blood pressure, cardiovascular disease, or a family history of kidney problems should ask whether regular testing is appropriate for them.
The Important Connection Between Kidneys, Bones, and Red Blood Cells
The kidneys contribute to health in ways that may surprise people. Their responsibilities include helping maintain strong bones and supporting the production of red blood cells.
Healthy kidneys activate vitamin D into a form that helps the body absorb calcium and maintain normal bone metabolism. When kidney function becomes significantly impaired, changes in vitamin D activation, calcium, phosphorus, and hormone levels can affect bone health.
Chronic kidney disease can also contribute to anemia. The kidneys produce a hormone called erythropoietin, which signals the bone marrow to make red blood cells. When the kidneys are damaged, they may produce less of this hormone. Iron deficiency, inflammation, and other factors can also contribute to anemia in people with kidney disease.