Kidney Function Tests

Kidney function tests check how effectively the kidneys are filtering waste products and excess fluid from the blood.

Main Tests

• Creatinine — a waste product from muscle activity that the kidneys filter out; levels rise when kidney function declines
• eGFR (estimated glomerular filtration rate) — calculated from creatinine, age, and other factors, this estimates how well the kidneys are filtering blood and is the primary way kidney function is staged
• Blood urea nitrogen (BUN) — another waste product filtered by the kidneys, though it's influenced by more factors than creatinine

Why These Tests Matter

Chronic kidney disease often develops silently over years without symptoms, particularly in its earlier stages. Diabetes and high blood pressure are the two leading causes of chronic kidney disease, which is why regular kidney function testing is a standard part of care for both conditions — this is why our diabetes guide recommends it as part of routine monitoring.

Understanding Results

eGFR results are generally staged from normal function down to kidney failure, with lower numbers indicating more reduced function. A single abnormal result is usually followed up with repeat testing, since factors like dehydration or certain medications can temporarily affect these values. A full assessment of chronic kidney disease risk combines eGFR with the UACR test, since the two together give a more complete picture than eGFR alone.