Kidney Function Test (KFT): Purpose, Normal Values, and Health Insights

Your kidneys may be small, but they are mighty. These bean-shaped organs filter waste, balance fluids, regulate blood pressure, and keep your body in chemical balance. When kidneys aren’t working properly, waste products and toxins build up in the blood—leading to serious health issues.

That’s where a Kidney Function Test (KFT) comes in. A KFT is a simple set of blood and urine tests that show how well your kidneys are functioning. Doctors often prescribe it if you have symptoms like frequent urination, swelling in the legs, or unexplained fatigue.

In this blog, we’ll walk through what a KFT is, its purpose, normal ranges, causes of abnormal results, and what your test report means.

What Is a Kidney Function Test (KFT)?

A Kidney Function Test (KFT) is a group of blood tests that measure waste products, electrolytes, and proteins to evaluate how efficiently your kidneys are working.

The test looks at:

• Blood Urea Nitrogen (BUN) – a waste product from protein breakdown
• Serum Creatinine – a byproduct of muscle metabolism
• Uric Acid – waste formed from purines (found in food and cells)
• Electrolytes – sodium, potassium, chloride, and bicarbonate
• Estimated Glomerular Filtration Rate (eGFR) – measures kidney filtering ability

Sometimes, urine tests are also included to detect protein, sugar, or blood in urine.

Why Is KFT Important?

Kidney problems often go unnoticed in the early stages. A KFT helps in:

• Diagnosing kidney disease early
• Monitoring existing kidney conditions
• Checking the impact of diabetes or high blood pressure on kidneys
• Guiding treatment decisions for kidney patients
• Tracking side effects of certain medications (like antibiotics or painkillers)

According to the World Health Organization (WHO), chronic kidney disease affects around 850 million people globally. Early diagnosis with KFT can prevent kidney failure and the need for dialysis.

Key Parameters in a Kidney Function Test

Here’s what a KFT typically measures and the normal ranges:

1. Serum Creatinine

• Waste product from muscles, filtered by kidneys
• Normal range:
  • Men: 0.7–1.3 mg/dL
  • Women: 0.6–1.1 mg/dL

2. Blood Urea Nitrogen (BUN)

• Byproduct of protein metabolism
• Normal range: 7–20 mg/dL

3. Uric Acid

• Excess can cause gout or kidney stones
• Normal range:
  • Men: 3.4–7.0 mg/dL
  • Women: 2.4–6.0 mg/dL

4. Electrolytes (Na, K, Cl, HCO3)

• Sodium: 135–145 mmol/L
• Potassium: 3.5–5.0 mmol/L
• Chloride: 96–106 mmol/L
• Bicarbonate (HCO3): 22–28 mmol/L

5. Estimated Glomerular Filtration Rate (eGFR)

• Estimates how well kidneys filter blood
• Normal range: Above 90 mL/min/1.73m²
• Below 60 may indicate kidney disease

Causes of High KFT Readings

Abnormal values may suggest:

• High creatinine: Kidney damage, dehydration, or muscle injury
• High BUN: Kidney disease, high-protein diet, gastrointestinal bleeding
• High uric acid: Gout, kidney stones, poor kidney function
• Electrolyte imbalance: Kidney dysfunction, dehydration, or hormonal disorders

Causes of Low KFT Readings

• Low creatinine: Low muscle mass, pregnancy, or poor nutrition
• Low BUN: Liver disease, malnutrition, overhydration
• Low uric acid: Rare, but may occur due to certain medications or liver disease

Symptoms That May Require a KFT

Doctors may recommend a KFT if you have:

• Swelling in ankles, feet, or face
• Frequent urination, especially at night
• Foamy or bloody urine
• Constant fatigue or weakness
• Unexplained weight loss
• High blood pressure
• Pain in the lower back or sides

How Is a KFT Done?

• A blood sample is drawn from a vein in your arm.
• Sometimes a urine sample is collected.
• No major preparation is required, but you may need to avoid protein-rich meals before the test.
• Results are usually available within 24–48 hours.

Interpreting KFT Reports

Here’s a quick breakdown:

• Creatinine above 1.5 mg/dL → Possible kidney disease
• BUN/Creatinine ratio high → Dehydration or GI bleeding
• Low eGFR (<60) → Chronic kidney disease
• High uric acid → Risk of gout or kidney stones

Always consult a doctor for proper interpretation.

Treatment Options for Abnormal KFT

Treatment depends on the underlying cause:

• For dehydration: Increase fluid intake
• For kidney infections: Antibiotics
• For chronic kidney disease (CKD): Lifestyle changes, blood pressure and sugar control, dialysis in severe cases
• For gout/high uric acid: Medications like allopurinol, diet changes
• For electrolyte imbalance: IV fluids, supplements, or medication adjustments

How to Keep Your Kidneys Healthy

• Drink enough water daily (2–3 liters, unless restricted by your doctor)
• Limit salt and processed foods
• Maintain a healthy weight
• Control diabetes and high blood pressure
• Avoid overuse of painkillers
• Eat more fruits, vegetables, and whole grains
• Get regular health check-ups if you have risk factors

Key Facts About Kidney Function Tests

• CDC (Centers for Disease Control and Prevention): 1 in 7 adults in the U.S. has chronic kidney disease, but most don’t know it.
• WHO: Chronic kidney disease causes at least 2.4 million deaths annually worldwide.
• KFT is a standard blood test prescribed for people with diabetes, hypertension, or suspected kidney issues.
• Early detection can prevent dialysis and kidney transplant in many cases.

FAQs About Kidney Function Test

What is a kidney function test (KFT)?

It’s a blood test that checks how well your kidneys are filtering waste.

What is the normal range of KFT?

Creatinine: 0.7–1.3 mg/dL (men), 0.6–1.1 mg/dL (women); BUN: 7–20 mg/dL.

What causes high creatinine in KFT?

Kidney disease, dehydration, or muscle injury.

Is fasting required for a kidney function test?

Not always, but sometimes fasting 8–12 hours is advised.

Can dehydration affect KFT results?

Yes, dehydration can raise creatinine and BUN levels.

What is a dangerous creatinine level?

Above 2.0 mg/dL in adults may indicate serious kidney problems.

Can high uric acid affect kidneys?

Yes, it can cause kidney stones and gout.

How often should I get a KFT?

Yearly if you have diabetes, hypertension, or a family history of kidney disease.

Can diet affect KFT results?

Yes, high-protein diets can raise BUN and uric acid.

What is eGFR in kidney test reports?

It estimates kidney filtering capacity; below 60 may indicate kidney disease.

Conclusion

A Kidney Function Test (KFT) is one of the most effective ways to check kidney health and detect problems early. Whether it’s high creatinine, abnormal uric acid, or low eGFR, these readings provide important insights into how well your kidneys are functioning.

At Molecular, we provide accurate diagnostic testing, including KFT, to help you take proactive steps toward better kidney health. Remember—early detection is the key to preventing kidney damage.