How to Read Your KFT Report: RFT Test Normal Range & Reference Values

A renal function test (RFT), also commonly called a kidney function test (KFT), is a group of blood and urine tests that are conducted to evaluate how well the kidneys work. The test measures markers for kidney health, such as creatinine and blood urea, electrolytes such as sodium, potassium and chloride. Depending on the tests recommended, the assessment may also include estimated glomerular filtration rate (eGFR), urinalysis, urine albumin, and glucose.

The RFT test normal range varies depending on the parameter being measured, the laboratory, and individual factors. Understanding the ranges may help read a KFT report and determine when a result might require further examination.

What are the Normal Ranges of Renal Function Test?

There is no single number that represents the KFT normal range. There are specific reference ranges for each parameter. The table below gives the common reference values for some important kidney-related tests.

These numbers are general reference points for the RFT normal value. They should not be used alone for diagnosis of a kidney disease. Some test results can be influenced by factors such as age, muscle mass, diet, fluid level, medicines, and underlying health conditions.

Understanding the Key RFT Parameters

Serum Creatinine

Creatinine is a waste product formed by normal muscle activity. It is filtered from the blood by the kidneys and excreted in urine. A blood creatinine test is commonly used to assess kidney function.

A high creatinine level can occur when kidney filtration is reduced. However, creatinine can also be influenced by factors such as muscle mass, diet, dehydration, and certain medical conditions or medicines. Therefore, it is generally interpreted alongside eGFR and other kidney tests. The RFT blood test normal values of creatinine do not rule out early kidney disease.

Blood Urea Nitrogen (BUN)

Blood urea nitrogen (BUN) test measures the amount of nitrogen in the blood that comes from urea. Urea is produced when the body breaks down protein. The kidneys filter urea from the blood so it can be excreted in urine.

A high BUN level may indicate decreased kidney function. It is to be noted that a BUN test alone cannot confirm a kidney condition. Therefore, BUN or blood urea test results should be interpreted alongside other markers of kidney function rather than in isolation.

Estimated Glomerular Filtration Rate (eGFR)

Estimated glomerular filtration rate (eGFR) is an indicator of how well the kidneys remove waste from the blood. It is commonly estimated using blood creatinine level and other patient information.

eGFR can naturally decrease with age. Therefore, an eGFR should not be used as the only indicator of kidney health, and the result should be compared to other indicators of kidney health, especially the urine albumin level and previous tests.

Urine Albumin-to-Creatinine Ratio (uACR)

The urine microalbumin creatinine ratio (uACR) test measures the amount of albumin in urine relative to creatinine. Normally, healthy kidneys do not allow the majority of the albumin to enter the urine. So, a rise in urine albumin can be indicative of kidney damage.

If the result is 30mg/g or more, this may mean that the person has albuminuria. However, one abnormal uACR test result is not necessarily a sign of kidney disease, and the test might have to be repeated.

Urine Protein-to-Creatinine Ratio (uPCR)

uPCR is a urine test that determines the level of total protein in urine relative to creatinine. Unlike uACR, which specifically measures albumin relative to creatinine, uPCR measures total protein relative to creatinine. The test can help detect and monitor proteinuria, which indicates an increased amount of protein in the urine and can be a sign of kidney disease.

Other than this, uPCR may also be used to assess and monitor protein loss in conditions such as IgA nephropathy, lupus nephritis, and glomerulonephritis.

What Does a Normal KFT Test Report Mean?

The RFT test normal range generally means the measured results fall within the laboratory's reference range. For kidney health, the RFT normal values are interpreted together because different tests assess different aspects of kidney function.

KFT Parameter	What a Normal Result Means?
Serum Creatinine	Creatinine levels within the laboratory’s reference range indicate that the kidneys are filtering out creatinine from the blood normally.
Blood Urea Nitrogen (BUN)	The amount of urea nitrogen in the blood is within the expected range.
Estimated Glomerular Filtration Rate (eGFR)	The kidneys' estimated ability to filter blood is not showing an obvious reduction.
Urine Protein-Creatinine Ratio (uPCR)	The normal KFT test report means there is no excess protein being detected in the urine.
Urine Albumin-to-Creatinine Ratio (uACR)	The amount of albumin in the urine is not unusually high.
Potassium	The blood potassium level in the normal range indicates that potassium balance is being maintained at the time of the test.
Calcium	This suggests that the calcium level is in the normal range; at the time of measurement there is no abnormality.
Uric Acid	The blood uric acid level is in the normal range, meaning the amount of waste product measured in the blood is not high.

What Can Affect RFT Results?

Conditions other than kidney disease can affect RFT values. The normal RFT values may vary depending on the person, including their diet, fluid intake, body weight, some medications, and medical conditions. Therefore, an abnormal value should be interpreted along with the other results in the report.

• Dehydration: Dehydration can raise BUN levels and may also impact the results for creatinine and eGFR.
• Diet: BUN and creatinine levels may change with a high-protein diet or consuming large amounts of cooked meat. Other dietary practices such as vegetarian or low-meat diets may also influence creatinine-based eGFR results.
• Muscle Mass: Creatinine levels may not accurately reflect kidney filtration in people with very high or very low muscle mass. This factor may also affect the estimated GFR.
• Nutrition: Malnutrition or undernutrition can influence the levels of creatinine and therefore influence eGFR estimates.
• Pregnancy: Pregnancy may affect creatinine-based eGFR estimates and should be
  interpreted cautiously.
• Physical Activity: Heavy exercise can temporarily raise creatinine and cause the eGFR to be lower than it may be.
• Medications: Some medications may have an effect on BUN, creatinine or eGFR.
• Diseases: The normal KFT report or how well eGFR is estimated can be affected by diseases such as liver disease, cirrhosis, nephrotic syndrome and chronic diseases.
• Urinary Tract Problems: Obstruction of the urinary tract can result in an increased BUN and could influence normal KFT values.

Who Should Take RFT?

Renal Function Test (RFT) can help detect kidney problems, particularly in people with risk factors. Testing may be recommended for those with:

• Diabetes: Diabetes is a major risk factor for chronic kidney disease. Diabetics may require frequent kidney tests such as blood and urine tests.
• High Blood Pressure: High blood pressure that is not controlled can cause the blood vessels in the kidneys to become damaged and impair the kidneys' ability to filter blood.
• Heart Disease or Heart Failure: Heart disease and failure are linked to a higher risk of kidney disease.
• Family History of Kidney Disease or Kidney Failure: Kidney disease or kidney failure can run in families and might make it more likely to develop chronic kidney disease.
• Acute Kidney Injury (AKI): History of acute kidney injury (AKI) is a known risk factor for chronic kidney disease (CKD).
• Older Age: Risk of chronic kidney disease (CKD) goes up with age especially after the age of 60.

Understanding the RFT normal values chart can help monitor kidney health, but a single test value does not provide the complete picture. The levels of creatinine, BUN, eGFR, and urine albumin should be taken together, along with other factors such as age, dietary habits, medication, and existing health conditions. If results are abnormal, seek the advice of a health care professional for proper interpretation and guidance.

Apollo Diagnostics offers diagnostic testing services, including kidney function testing. Speak with a healthcare professional about which tests may be appropriate based on your health and risk factors.

Frequently Asked Questions

Can RFT detect kidney damage?

Yes. An RFT can help identify kidney damage by evaluating kidney filtration and measuring the presence of certain substances like albumin in the urine. The eGFR is a measure of how well the kidneys filter blood, and the urine albumin-to-creatinine ratio (uACR) can detect increased albumin into the urine, which can signify that the filtering units of the kidney are damaged.

What is the normal value of RFT?

The RFT test normal range varies based on the parameters that are measured. The most assessed include creatinine, BUN, eGFR, electrolytes, and urine albumin. They each have a reference interval, and there is no one normal value for a KFT.

Is a Creatinine Level of 1.0 mg/dL Normal?

Creatinine levels of 1.0 mg/dL might be within the generally accepted reference intervals for adults, but interpretation depends on laboratory's reference interval, sex, age, muscle mass, and other factors. Creatinine should be taken together with eGFR and other kidney tests.

What is the normal eGFR?

In adults, an eGFR ? 90 mL/min/1.73 m² is considered normal. But eGFR decreases naturally as people get older, and doctors use the result together with other information.

Can Kidney Disease be Present with Normal Creatinine?

Yes. At the early stage of kidney disease, creatinine may be within a reference range. Therefore, eGFR and urine albumin testing may be used in addition to creatinine by healthcare professionals.

What Does a High Creatinine Level Mean?

An increased creatinine level can occur when kidney filtration is reduced, but it can also be influenced by several other factors such as dehydration, heavy exercise, muscle mass, diet and certain medicines. A healthcare professional may recommend repeat or additional testing to determine the cause.

What Should I Do if my RFT Result is Abnormal?

If the RFT result is abnormal, a healthcare professional may suggest repeat testing or further investigations, such as complete urine examination (CUE) Test, kidney ultrasound or imaging, or in some cases, kidney biopsy. Persistent abnormalities may require further evaluation for kidney disease.