“Kidney disease is the most under-diagnosed chronic condition in India. By the time symptoms appear, patients have often lost 70% of kidney function. A simple creatinine test costing ₹150 can catch it years earlier.”
— Truemark Health Editorial Team, Medically Reviewed by NABL-Certified Professionals
What Is a Kidney Function Test (KFT)?
A Kidney Function Test (KFT), also called a Renal Function Test (RFT), is a group of blood tests that evaluate how well your kidneys are filtering waste products from your blood. The kidneys filter approximately 180 liters of blood daily, removing toxins and maintaining fluid and electrolyte balance.
The standard KFT panel includes Serum Creatinine, Blood Urea Nitrogen (BUN), Blood Urea, eGFR (estimated Glomerular Filtration Rate), Uric Acid, and electrolytes (Sodium, Potassium, Chloride, Calcium, Phosphorus).
Chronic kidney disease (CKD) affects an estimated 17% of the Indian population. It is often called a "silent disease" because symptoms appear only when kidney function has declined to below 30% of normal capacity. Early detection through routine KFT testing is critical.
Creatinine and eGFR: The Key Kidney Markers
Serum Creatinine is the most widely used kidney marker. Creatinine is a waste product from muscle metabolism, filtered exclusively by the kidneys. When kidney function declines, creatinine accumulates in the blood.
Normal creatinine levels are 0.7–1.3 mg/dL for men and 0.6–1.1 mg/dL for women. However, creatinine alone can be misleading — a muscular young man may have higher creatinine without kidney disease, while an elderly person with sarcopenia (muscle wasting) may have "normal" creatinine despite significant kidney damage.
eGFR (estimated Glomerular Filtration Rate) corrects for age, sex, and race, giving a more accurate picture. Normal eGFR is above 90 mL/min/1.73m². Stages of CKD: Stage 1 (eGFR >90 with other evidence), Stage 2 (60–89), Stage 3 (30–59), Stage 4 (15–29), Stage 5 (<15 — dialysis range).
BUN, Urea, and Uric Acid
Blood Urea Nitrogen (BUN) measures the nitrogen from urea, a waste product of protein metabolism. Normal BUN is 7–20 mg/dL. The BUN/Creatinine ratio helps differentiate causes of kidney dysfunction — a ratio above 20:1 suggests dehydration or gastrointestinal bleeding rather than intrinsic kidney disease.
Blood Urea (15–40 mg/dL) is related to BUN but measured differently. Elevated urea suggests impaired kidney filtration, high protein intake, dehydration, or gastrointestinal bleeding.
Uric Acid (Men: 3.4–7.0 mg/dL, Women: 2.4–6.0 mg/dL) is a waste product from purine metabolism. Elevated uric acid can cause gout (painful joint inflammation) and is associated with kidney stones. High uric acid is increasingly recognized as an independent risk factor for kidney disease and cardiovascular disease.
Electrolytes and Their Role in Kidney Health
The kidneys play a central role in maintaining electrolyte balance. Electrolyte abnormalities are often the first sign of kidney dysfunction.
Potassium (3.5–5.0 mEq/L) is critically important — both high and low levels can cause life-threatening cardiac arrhythmias. Kidney disease commonly causes high potassium (hyperkalemia), which is why potassium monitoring is essential.
Sodium (136–145 mEq/L) abnormalities reflect the kidneys' ability to manage water balance. Calcium and Phosphorus are regulated by the kidneys working in concert with parathyroid hormone and Vitamin D. In advanced kidney disease, calcium drops and phosphorus rises, leading to bone disease.
Normal Range Reference Table
| Parameter | Normal Range | Unit | High Indicates | Low Indicates |
|---|---|---|---|---|
| Serum Creatinine (Male) | 0.7–1.3 | mg/dL | Kidney dysfunction | — |
| Serum Creatinine (Female) | 0.6–1.1 | mg/dL | Kidney dysfunction | — |
| BUN | 7–20 | mg/dL | Kidney disease, dehydration | — |
| Blood Urea | 15–40 | mg/dL | Kidney disease | — |
| eGFR (Normal) | >90 | mL/min | — | Kidney disease staging |
| Uric Acid (Male) | 3.4–7.0 | mg/dL | Gout, kidney stones | — |
| Uric Acid (Female) | 2.4–6.0 | mg/dL | Gout, kidney stones | — |
| Sodium | 136–145 | mEq/L | — | — |
| Potassium | 3.5–5.0 | mEq/L | Cardiac risk | Cardiac risk |
| Calcium | 8.5–10.5 | mg/dL | — | — |
| Phosphorus | 2.5–4.5 | mg/dL | CKD progression | — |
Serum Creatinine (Male)
Serum Creatinine (Female)
BUN
Blood Urea
eGFR (Normal)
Uric Acid (Male)
Uric Acid (Female)
Sodium
Potassium
Calcium
Phosphorus
Frequently Asked Questions
Is fasting required for a kidney function test?
What does high creatinine mean?
Can kidney disease be reversed?
Who should get regular kidney function tests?
Truemark Health Editorial Team
Medically Reviewed by NABL-Certified Professionals
The Truemark Health Editorial Team produces evidence-based health content reviewed against current clinical guidelines, ICMR standards, and peer-reviewed research. Every article is vetted for medical accuracy before publication.
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