"What is Renal Function Test (RFT): Types, Normal Ranges, and Kidney Health Explained"

 🌿 What is Renal Function Test (RFT)?

A Renal Function Test (RFT) is a group of blood and urine tests that check how well your kidneys are working.

Kidneys filter waste products, balance electrolytes, and maintain fluid balance. If kidneys are damaged, waste products build up in blood.

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🏥 Where Can You Do an RFT Test?

• At any hospital laboratory

• Diagnostic labs like Shaukat Khanum, Chughtai, Aga Khan, Shifa, or private diagnostic centers

• Pathology labs in clinics
  Doctors often prescribe RFT when they suspect kidney issues like high blood pressure, diabetes, or swelling.

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🧪 What Types of Tests Are Included in RFT?

RFT usually includes:

1. Blood Urea Nitrogen (BUN)

2. Serum Creatinine

3. eGFR (Estimated Glomerular Filtration Rate)

4. Uric Acid

5. Electrolytes (Sodium, Potassium, Chloride, Bicarbonate)

6. Sometimes Urine Routine Examination

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🔹 1. Urea Nitrogen in Blood (BUN Test)

• Measures the amount of urea nitrogen (a waste product formed from protein breakdown) in the blood.

• Kidneys normally remove urea from blood through urine. High levels suggest reduced kidney function.

Normal Range:

• Adults: 7 – 20 mg/dL

Example:

• A patient with BUN = 35 mg/dL may have kidney disease, dehydration, or high-protein diet.

• A patient with BUN = 12 mg/dL is within the normal range.

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🔹 2. Serum Creatinine Test

• Creatinine is a waste product from muscle metabolism.

• Kidneys filter creatinine; if kidney function is low, creatinine rises.

• It’s one of the most reliable single markers of kidney function.

Normal Range:

• Men: 0.7 – 1.3 mg/dL

• Women: 0.6 – 1.1 mg/dL

Example:

• If Creatinine = 2.0 mg/dL, it may indicate kidney impairment.

• If Creatinine = 0.9 mg/dL, kidney function is normal.

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🔹 3. eGFR (Estimated Glomerular Filtration Rate)

• eGFR estimates how much blood kidneys filter per minute.

• It is calculated using Creatinine level, Age, Sex, and sometimes Race.

• It helps detect Chronic Kidney Disease (CKD).

Normal Range:

• 90 – 120 mL/min/1.73m² = Normal

• 60 – 89 mL/min/1.73m² = Mildly decreased function

• 30 – 59 mL/min/1.73m² = Moderate CKD

• 15 – 29 mL/min/1.73m² = Severe CKD

• <15 mL/min/1.73m² = Kidney failure (dialysis may be needed)

Example:

• eGFR = 95 → Normal kidneys

• eGFR = 35 → Stage 3 CKD (moderate disease)

🔬 Types of Tests in RFT

An RFT usually includes:

1. Blood Urea Nitrogen (BUN)

2. Serum Creatinine

3. Estimated Glomerular Filtration Rate (eGFR)

4. Uric Acid

5. Electrolytes (Sodium, Potassium, Chloride, Bicarbonate)

6. Urine Examination

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🔹 1. Blood Urea Nitrogen (BUN) Test

• Purpose: Measures nitrogen waste from protein breakdown.

• Normal Range: 7 – 20 mg/dL

• Example:

  • 35 mg/dL → May indicate kidney disease or dehydration.

  • 12 mg/dL → Normal.

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🔹 2. Serum Creatinine Test

• Purpose: Checks creatinine (waste from muscles). High levels = poor kidney function.

• Normal Range:

  • Men: 0.7 – 1.3 mg/dL

  • Women: 0.6 – 1.1 mg/dL

• Example:

  • 2.0 mg/dL → Possible kidney impairment.

  • 0.9 mg/dL → Normal.

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🔹 3. eGFR (Estimated Glomerular Filtration Rate)

• Purpose: Estimates how well kidneys filter blood per minute. Detects Chronic Kidney Disease (CKD).

• Normal Range:

  • 90 – 120 = Normal

  • 60 – 89 = Mildly low

  • 30 – 59 = Moderate CKD

  • 15 – 29 = Severe CKD

  • <15 = Kidney failure

• Example:

  • 95 → Healthy kidneys.

  • 35 → Stage 3 CKD.

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🔹 4. Uric Acid Test

• Purpose: Checks uric acid (waste from purines). High levels can cause gout, kidney stones, or kidney damage.

• Normal Range:

  • Men: 3.4 – 7.0 mg/dL

  • Women: 2.4 – 6.0 mg/dL

• Example:

  • 8.5 mg/dL → Risk of gout/kidney issue.

  • 4.0 mg/dL → Normal.

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🔹 5. Electrolyte Tests (Na, K, Cl, HCO₃)

• Purpose: Check the balance of salts and fluids in the body. Imbalances may mean kidney disease, dehydration, or heart problems.

• Normal Range:

  • Sodium: 135 – 145 mmol/L

  • Potassium: 3.5 – 5.0 mmol/L

  • Chloride: 98 – 106 mmol/L

  • Bicarbonate: 22 – 29 mmol/L

• Example:

  • Na 150 → Dehydration.

  • K 6.0 → Kidney failure risk.

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🔹 6. Urine Examination

• Purpose: Detects protein, blood, or glucose in urine. These can signal kidney damage or infection.

• Normal Range: No protein, no blood, no glucose.

• Example:

  • Protein in urine → Kidney damage.

  • Blood in urine → Infection or stones.

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✅ Quick Summary Table

Test	Normal Range	High/Low Indication
BUN	7 – 20 mg/dL	High → kidney issue, dehydration
Creatinine	M: 0.7 – 1.3 mg/dL F: 0.6 – 1.1 mg/dL	High → kidney damage
eGFR	90 – 120 = Normal	Low → CKD stages
Uric Acid	M: 3.4 – 7.0 F: 2.4 – 6.0 mg/dL	High → gout, stones
Sodium	135 – 145 mmol/L	High → dehydration
Potassium	3.5 – 5.0 mmol/L	High → kidney failure risk
Urine Test	No protein/blood/glucose	Abnormal → kidney/infection

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👉 Final Note:

RFT helps in early detection of kidney problems. Always consult a doctor or nephrologist for correct interpretation, since lifestyle, diet, and other diseases also affect results.