Kidney Function Tests (KFTs): Introduction, Test Result, Unit, Reference Range, Test Methods,and Keynotes


Kidney Function Tests (KFTs), also known as Renal Function Tests (RFTs), are a group of laboratory tests that provide important information about the functioning of the kidneys. These tests help doctors assess the health of the kidneys, detect kidney diseases, and monitor the effectiveness of treatments.

The main kidney function tests include:

  1. Serum Creatinine: Creatinine is a waste product produced by muscles that is filtered out of the blood by the kidneys. Elevated levels of serum creatinine can indicate reduced kidney function.
  2. Blood Urea Nitrogen (BUN): BUN is a measure of the amount of nitrogen in the blood that comes from the waste product urea. Urea is produced when the body breaks down proteins. High BUN levels can be a sign of kidney dysfunction.
  3. Estimated Glomerular Filtration Rate (eGFR): The eGFR is a calculated value that estimates how well the kidneys are filtering waste products from the blood. It is usually reported alongside creatinine levels and is used to assess kidney function.
  4. Urinalysis: This test analyzes a urine sample to check for the presence of protein, blood cells, glucose, and other substances that can indicate kidney problems or urinary tract issues.
  5. Albumin-to-Creatinine Ratio (ACR): This test measures the amount of albumin (a type of protein) in the urine relative to the creatinine level. Elevated ACR levels can indicate kidney damage or early signs of kidney disease.
  6. Blood Electrolytes (Sodium, Potassium, and Bicarbonate): These tests assess the balance of important electrolytes in the blood, which can be affected by kidney function.
  7. Serum Calcium and Phosphorus: Kidneys play a role in regulating calcium and phosphorus levels in the blood. Abnormal levels can indicate kidney dysfunction.
  8. Serum Uric Acid: High levels of uric acid can lead to conditions like gout and can also be associated with kidney problems.

Test Result, Unit, Reference Range, and Test Methods

Kidney Function Tests (KFTs)-Introduction, Test Result, Unit, Reference Range, Test Methods,and Keynotes
Fig, Kidney Function Tests (KFTs)-Test Result, Unit, Reference Range, and Test Methods

Clinical Significance

Kidney Function Tests (KFTs) are of significant clinical importance as they provide essential information about the health and functioning of the kidneys. These tests are used by healthcare providers to:

  1. Diagnose Kidney Diseases: Abnormal results in KFTs can indicate various kidney disorders, such as chronic kidney disease (CKD), acute kidney injury (AKI), glomerulonephritis, kidney stones, and urinary tract infections. Early detection of kidney diseases allows for prompt treatment and management to prevent further complications.
  2. Monitor Kidney Function: Patients with known kidney problems or those at risk of kidney disease, such as individuals with diabetes or hypertension, require regular monitoring of their kidney function. KFTs help track changes in kidney function over time, enabling healthcare providers to adjust treatment plans accordingly.
  3. Evaluate Overall Health: The kidneys play a vital role in filtering waste products and excess fluids from the blood. Abnormal kidney function can lead to the accumulation of toxins and electrolyte imbalances, which can affect other organ systems and overall health.
  4. Assess Medication Safety: Certain medications, especially those cleared by the kidneys, can pose a risk to individuals with impaired kidney function. KFTs are used to determine the appropriate dosage of medications and to avoid potential toxicity.
  5. Preoperative Assessment: Before surgeries or certain medical procedures, KFTs are often performed to ensure that the kidneys can tolerate anesthesia and other medications used during the procedure.
  6. Monitor Treatment Efficacy: For patients with kidney diseases, KFTs are used to evaluate the effectiveness of treatments, such as medications, dietary changes, or dialysis.
  7. Identify Risk Factors: KFTs can help identify risk factors for kidney disease, such as high blood pressure, diabetes, or a family history of kidney problems. Early identification of risk factors allows for preventive measures to reduce the likelihood of developing kidney diseases.
  8. Kidney Donor Evaluation: For individuals considering kidney donation, KFTs are a critical part of the evaluation process to ensure that the donor’s kidneys are healthy and suitable for transplantation.


Keynotes on Kidney Function Tests (KFTs):

  1. Purpose: Kidney Function Tests (KFTs), also known as Renal Function Tests (RFTs), assess the health and functioning of the kidneys. They help diagnose kidney diseases, monitor kidney function, and guide treatment decisions.
  2. Common Tests: KFTs include serum creatinine, blood urea nitrogen (BUN), estimated glomerular filtration rate (eGFR), urinalysis, albumin-to-creatinine ratio (ACR), and blood electrolytes (sodium, potassium, bicarbonate).
  3. Creatinine and eGFR: Serum creatinine is a waste product from muscles, and eGFR estimates the kidney’s ability to filter waste. Elevated creatinine and decreased eGFR indicate reduced kidney function.
  4. BUN: Blood urea nitrogen is a measure of nitrogen in the blood from protein breakdown. High BUN levels may indicate kidney dysfunction but can be influenced by other factors.
  5. Urinalysis: This examines a urine sample for signs of kidney damage, such as the presence of protein, blood cells, glucose, and other substances.
  6. ACR: Measures the ratio of albumin to creatinine in urine and helps detect early signs of kidney damage or disease.
  7. Blood Electrolytes: Sodium, potassium, and bicarbonate levels in the blood can be affected by kidney function and are important for overall health.
  8. Clinical Significance: KFTs help diagnose kidney diseases (chronic kidney disease, acute kidney injury, etc.), monitor kidney function in at-risk individuals, and assess overall health.
  9. Medication Safety: KFTs guide medication dosing and safety, especially for drugs cleared by the kidneys.
  10. Preoperative Evaluation: KFTs are used to assess kidney health before surgeries and certain medical procedures.
  11. Treatment Monitoring: KFTs help evaluate the effectiveness of treatments for kidney diseases.
  12. Risk Identification: They identify risk factors for kidney disease, such as hypertension, diabetes, or family history.
  13. Kidney Donor Evaluation: KFTs are crucial for assessing kidney donors’ suitability for transplantation.
  14. Interpretation: KFTs are interpreted alongside clinical information and imaging studies for a comprehensive diagnosis.
  15. Early Detection: Early identification of kidney problems through KFTs allows for timely interventions, improving patient outcomes.
  16. Follow-up Testing: Regular KFTs are necessary for individuals with kidney diseases or at risk of kidney issues to monitor progression and response to treatment.
  17. Comprehensive Assessment: KFTs are part of a broader evaluation that includes medical history, physical examination, and imaging studies.
  18. Medical Professional Consultation: Abnormal KFT results should be discussed with a healthcare provider for appropriate evaluation and management.

Further Readings

  1. National Kidney Foundation (NKF) – Kidney Function Tests: The NKF provides comprehensive information on kidney function tests, their purpose, how they are performed, and what the results mean. Visit their website for patient resources and educational materials. (Website:
  2. The National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK) – Kidney Disease Tests: NIDDK offers in-depth information on various kidney function tests, their clinical significance, and how they are used to diagnose and monitor kidney diseases. (Website:
  3. Kidney International: This peer-reviewed medical journal covers a wide range of topics related to kidney function, kidney diseases, and kidney function tests. You can access research articles and review papers to deepen your understanding of the subject. (Website:
  4. Journal of the American Society of Nephrology (JASN): JASN is a prominent journal that publishes original research and clinical studies related to kidney function and kidney diseases. It offers valuable insights into the latest advancements in the field of nephrology. (Website:
  5. UpToDate – Kidney Function Tests: UpToDate is a reliable resource used by healthcare professionals worldwide. It provides comprehensive, evidence-based information on various kidney function tests and their clinical interpretation. (Website:
  6. Lab Tests Online: This website offers easy-to-understand explanations of laboratory tests, including kidney function tests. It provides information on the purpose of the tests, how they are performed, and what the results mean. (Website:
  7. The American Journal of Kidney Diseases (AJKD): AJKD publishes research articles, clinical studies, and reviews related to kidney diseases, renal function, and kidney function tests. Accessing this journal can help you stay up-to-date with the latest developments in nephrology. (Website:

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