A kidney function test (KFT), also called a renal function test (RFT), is a group of blood tests that checks how well your kidneys filter waste. It usually measures creatinine, urea (or BUN), uric acid, electrolytes such as sodium and potassium, and an estimated GFR (eGFR). It helps detect kidney disease early, when it usually has no symptoms.
What does the kidney function test measure?
Your kidneys filter about 150–180 litres of blood a day, removing waste and extra fluid and balancing salts. Chronic kidney disease (CKD) develops silently: most people feel nothing until a large share of kidney function is lost. Diabetes and high blood pressure, both very common in India, are its leading causes.
A KFT panel looks at several markers together:
- Creatinine: A waste product from muscle. When kidneys filter less, creatinine builds up. It is the key marker in the panel.
- eGFR (estimated glomerular filtration rate): Calculated from creatinine, age and sex. It estimates how much blood your kidneys filter per minute and is used to stage kidney disease.
- Urea / blood urea nitrogen (BUN): A waste product from protein breakdown. It also rises with dehydration or a high-protein diet.
- Uric acid: A waste product linked to gout and kidney stones.
- Electrolytes (sodium, potassium, chloride): Kidneys keep these in a tight range; imbalances can affect the heart and muscles.
- Calcium and phosphorus: Included in some panels, as kidney disease disturbs their balance.
For people with diabetes, a urine albumin test (urine ACR) is often added, as protein in urine is frequently the earliest sign of kidney damage.
KFT normal range (adults)
Women 0.6–1.1 mg/dL
60–89 can be normal with age
Below 60 for 3+ months suggests CKD
Women 2.4–6.0 mg/dL
Where does your result fall?
Enter your eGFR value from your report. A low eGFR only suggests chronic kidney disease if it stays low for 3 months or more.
A general guide, not a diagnosis. The reference range on your own report takes priority, and a doctor should interpret any result outside it.
Ranges vary between labs and methods. Always compare your result with the reference range printed on your own report.
What abnormal results can mean
- High creatinine / low eGFR: Can suggest reduced kidney function. Dehydration, heavy exercise, a very high-protein diet or creatine supplements can raise creatinine temporarily.
- High urea: Can suggest dehydration, high protein intake, kidney problems or bleeding in the gut.
- High potassium: Needs prompt attention, as it can affect heart rhythm. Can also be a false result if the sample is handled poorly.
- Low sodium: Can occur with some medicines (such as certain BP tablets), excessive water intake or illness.
Your doctor will look at trends over time; one result rarely tells the full story.
Who should get this test?
- Everyone with diabetes or high blood pressure, at least once a year.
- People with a family history of kidney disease, obesity, or past kidney stones.
- Adults over 40 as part of a routine health checkup.
- People on long-term medicines that can affect kidneys, including regular painkillers (NSAIDs).
- Anyone with symptoms: swelling in the feet or face, foamy urine, reduced urine, or persistent fatigue.
- Preparation: Usually no fasting needed, though some labs advise 8–12 hours if combined with other tests. Avoid heavy exercise and very high-protein meals the day before.
This page is for general information and is not a substitute for medical advice. Always interpret your results with a qualified doctor.