Kidney Function Test - Types, Procedure, and Normal Ranges

A kidney function test (also called a renal function test) is a set of blood and urine tests used to evaluate how well your kidneys are filtering waste, maintaining fluid balance, and regulating important minerals.

These tests measure substances like creatinine, urea, and electrolytes that accumulate when your kidneys aren’t functioning properly.

In simple terms, If your kidney function test results are abnormal, it may indicate early kidney disease, dehydration, or another underlying condition affecting kidney performance.

The kidneys perform several essential functions:

• Filtering waste and toxins from your blood
• Balancing fluids and electrolytes (sodium, potassium, calcium)
• Regulating blood pressure
• Supporting red blood cell production via erythropoietin
• Activating vitamin D for bone health

When your kidneys don’t work well, waste builds up in your body, leading to fatigue, swelling, and more serious complications such as chronic kidney disease (CKD).

According to the World Health Organization (WHO) and the National Kidney Foundation (NKF), early detection through a simple kidney function test can:

• Prevent progression to kidney failure
• Help manage diabetes or hypertension better
• Reduce long-term health risks

Blood Tests for Kidney Function

Serum Creatinine Test

• Measures the amount of creatinine, a waste product from muscle metabolism.
• High levels may indicate kidney dysfunction.
• Normal range:
• Men: 0.74–1.35 mg/dL
• Women: 0.59–1.04 mg/dL

Estimated Glomerular Filtration Rate (eGFR)

• Calculated using your serum creatinine, age, gender, and race.
• Indicates how efficiently the kidneys are filtering blood.
• Normal eGFR: 90 mL/min/1.73m² or higher
• An eGFR below 60 suggests possible kidney damage.

Blood Urea Nitrogen (BUN)

• Measures the amount of nitrogen in your blood that comes from urea, a waste product.
• Normal range: 7–20 mg/dL

Electrolyte Tests (Sodium, Potassium, Calcium, Phosphate)

• Imbalances can indicate kidney problems or dehydration.

1. Urinalysis

• Detects protein, glucose, blood, and bacteria in urine.
• Helps identify infections or kidney damage.

2. Urine Albumin-to-Creatinine Ratio (UACR)

• Measures how much albumin (a protein) leaks into the urine.
• Normal: <30 mg/g
• Persistent high levels may indicate early kidney disease.

3. Hour Urine Collection Test

• Measures total urine output and waste products over a day.
• Useful for assessing kidney filtration and protein loss.

Test

Normal Range

Abnormal Range (Possible Concern)

Serum Creatinine

0.6–1.3 mg/dL

Above 1.5 mg/dL

eGFR

90+ mL/min/1.73m²

Below 60 = Kidney impairment

BUN

7–20 mg/dL

>25 mg/dL = Possible kidney issue

UACR

<30 mg/g

>30 mg/g = Kidney disease marker

Sodium

135–145 mEq/L

<130 or >150 mEq/L abnormal

(Sources: Mayo Clinic, National Kidney Foundation, NIH)

• Fasting: Usually not required unless combined with other tests.
• Hydration: Drink water, but avoid excessive fluids before testing.
• Medication Disclosure: Inform your doctor about medicines like antibiotics, NSAIDs, or blood pressure drugs.
• Avoid Protein Supplements: They can temporarily affect creatinine levels.

• High Creatinine or Low eGFR: Indicates reduced kidney filtration.
• High BUN: May mean kidney damage or dehydration.
• Protein in Urine: Suggests early kidney disease or diabetes-related nephropathy.

Always consult a nephrologist for proper interpretation — one abnormal reading doesn’t always mean disease.

You should consider a kidney test if you have:

• Diabetes or hypertension
• Family history of kidney disease
• Persistent swelling in the ankles or feet
• Changes in urination (color, frequency, or foaming)
• Chronic fatigue or nausea

The American Diabetes Association recommends annual kidney testing for all diabetics.

• Uncontrolled diabetes or hypertension
• Obesity
• Smoking
• Heart disease
• Frequent painkiller use (NSAIDs)
• Older age

According to the CDC, around 1 in 7 adults in the U.S. has chronic kidney disease, and most don’t know it.

• Stay hydrated
• Control blood sugar and blood pressure
• Limit salt and processed foods
• Avoid smoking and alcohol
• Exercise regularly
• Get regular checkups, especially if at risk

Pro tip: Schedule routine tests at trusted diagnostic centers like Nephrocare India to monitor your renal health early.

A kidney function test is one of the simplest yet most powerful tools for detecting kidney disease early.

Regular testing ensures your kidneys stay healthy and can prevent serious complications.

If you experience symptoms like swelling, fatigue, or changes in urination, don’t delay.

Consult a nephrologist or visit a trusted diagnostic center like Nephrocare India for a comprehensive kidney function evaluation.

This article is for informational purposes only and should not replace medical advice, diagnosis, or treatment. Always consult a qualified healthcare provider for personalized guidance.