What Does A Kidney Function Test Mean And How Do I Read An Index?

When doctors suspect signs of kidney disease, they will order their patients a kidney function test to check. But not everyone is familiar with what kidney function tests include, what problems should be noted and how it costs?

If you are concerned about the problem of kidney test packages, please find out useful information through the article below!

Currently, to evaluate kidney function when there are abnormal signs, patients must conduct many different tests such as taking samples from blood and urine.

Depending on the condition of the disease, not everyone needs to undergo all kidney function tests to be able to comprehensively assess kidney function.


Biochemical Blood Test

The laboratory tests to assess blood biochemical kidney function include common tests such as:

1. Blood urea test

When protein degrades, a product in the form of urea is produced. This is considered a type of waste that will be filtered through the glomeruli and then excreted through the urine.

If kidney function is impaired, blood urea concentration will be high. Through blood urea index test, it can help assess whether kidney function is working stably or not.


  • When the blood urea value is in the range of: 2.5 – 7.5 mmol / l, it shows the index of normal kidney function.
  • When the blood urea value increases, the patient is likely to suffer from diseases such as tubular inflammation, glomerulonephritis, signs of kidney stones, ureteral stones, or dehydration due to too high fever, diarrhea, congestive heart failure. 

In the case of patients eating foods that provide less protein to the body, impaired liver function or infusion, the value of urea in the blood will decrease.

2. Serum creatinine test


When creatin in the muscle is degraded, it will be converted to creatinine, which is mainly eliminated by the kidneys. Due to the Creatinine Index it will be possible to evaluate kidney function.

The Creatinine Index is normal in the range of:

  • For men: 0.6 – 1.2 mg / dl.
  • For women: 0.5 – 1.1 mg / dl.

If the creatinine index is above the allowable level, this is a sign of a disorder in the kidney function, because the ability to filter creatinine is impaired and the concentration of this substance in the blood will rise above normal.

The creatinine index also reflects the stage of kidney failure as follows:

  • Stage I renal failure: creatinine <130 mmol / l.
  • Kidney failure stage II: creatinine in the range 130 – 299 mmol / l.
  • Kidney failure stage III: creatinine in the range 300-899 mmol / l.
  • Stage IV kidney failure: creatinine is 900 mmol / l higher than the level.

However, the creatinine index test results are also influenced by many factors such as age, gender and muscle mass of each person will differ.

So when there are doubts about the accuracy of the creatinine test results, the doctor will order the patient to perform another test, blood cystatin C.

Normal values ​​of blood cystatin C in the range: 0.31 – 0.99 mg / L.

3. Electrolytes

Electrolyte imbalances are mainly caused by impaired kidney function, including:

Sodium (Sodium): Normal values ​​of sodium in the blood range from 135 to 145 mmol / L.

But for patients with kidney failure, the concentration of sodium in the blood is significantly reduced due to loss from the gastrointestinal tract, through the kidneys and through the skin, or due to excess water.

Potassium (Potassium): The normal value of Potassium in the blood ranges from 3.5 to 4.5 mmol / L. For patients with kidney failure, the elimination of toxic substances is poor, which leads to a high concentration of potassium in the blood.

Blood calcium: The normal value of calcium in the blood for people in good health is about 2.2 – 2.6 mmol / L. In patients with renal impairment, the calcium concentration in the blood decreases but the phosphate increases.

4. Get tested for the acid-base disorder

The acid-base disorder test is one of the most common kidney function tests ordered when patients with kidney disease are suspected.

The concentration of pH in the blood is at the average level when it is in the range of 7.37 – 7.43. If kidney function is impaired, it increases the concentration of acid in the blood, which in turn helps detect kidney problems.

5. Test for uric acid in the blood

Uric acid levels in the blood are normal in the range:

  • For men: 180 – 420 mmol / l.
  • For women: 150 – 360 mmol / l.

This test is used when the patient is suspected of having kidney disease or even gout.

If the level of uric acid in the blood increases meaning that the patient has kidney disease or gout, this time will conduct more tests and recommend treatment.

6. Other biochemical blood tests

General blood cell analysis: When the amount of red blood cells decreases, the likelihood of the patient developing chronic renal failure.

Serum Albumin: For healthy people, serum Albumin is at 35-50g / L, accounting for 50-60% of total protein. But when suffering from acute glomerulonephritis, the serum Albumin index falls low.

Total plasma protein: For healthy people, it is between 60 and 80 g / L, but when kidney filtration is problematic, the total protein index tends to decrease.

A Urine Test Assesses Kidney Function

1. General analysis of urine

One of the ways to check for weak or healthy kidneys is through a total urine analysis test.

The proportion of normal urine is in the range 1.01 – 1.020. For patients with impaired renal function, there is a lower density due to reduced urine concentration.


Protein in the urine sample also plays a role in assisting doctors in deciding whether or not to assign patients to the 24-hour proteinuria quantitative test.

2. Quantitative proteinuria 24 hours

For people with normal health, protein in urine will range from 0 – 0.2g / l / 24h.

But when patients with kidney disease such as kidney failure, glomerular damage, hypertension, diabetes, the proteinuria in the sample usually increase at 0.3g / l / 24h.

3. Imaging

For a comprehensive assessment of kidney function, doctors often combine both radiological methods with urine and blood tests to get more accurate conclusions.

4. Abdominal ultrasound

Through the abdominal ultrasound will help doctors detect kidney water retention caused by obstruction of the ureter.

Renal fluid retention on both sides is likely to lead to the risk of either chronic or acute kidney failure, in addition to helping detect congenital or genetic polycystic kidneys.

Base on ultrasound images, the kidneys will be smaller than normal, lose the medullary cortex distinction, change the structure, or have many cysts, thereby helping to suggest the risk of chronic kidney.

In addition, ultrasound also has the ability to detect tumors in the kidneys, or kidney stones.

5. CT scan

CT scan is most often used when the doctor suspects the patient has kidney failure or obstruction of the urinary tract.

Thanks to the method of using X-rays to target a position in the abdominal cavity allows clear images of the entire urinary system.

In order to detect the cause of the obstruction of the ureter and the location of the obstruction, a CT scan will have to incorporate injection of a contrast agent to help build an image of the entire urinary tract.

6. Kidney scintigraphy with radioisotopes

This is the only test method capable of evaluating the kidney function on each side and helping to evaluate the degree of ureteral obstruction with high effectiveness.

Thanks to this method, the doctor will clearly see the filtering function of each kidney, the degree of functional participation of each kidney, and the percentage of perfusion.

Some Notes of Testing Kidney Function

A very big question of patients is fasting kidney function tests or not? In order to avoid compromising results, there are a number of problems patients should pay attention to such as:

  • Normally, to perform kidney function tests, patients must fast for at least 8-10 hours before the procedure.
  • Not using stimulants will affect the test results.
  • The foods rich in protein can increase uric acid in the blood should be limited.

Patients should be consulted by a doctor about issues to note before doing the test. Besides, it is necessary to inform the doctor about the medicines that are being used to avoid affecting the results.

Where Is The Kidney Function Test?

When there are signs related to impaired kidney function, many people often worry that kidney function tests should be reputable? What is included in the kidney function test package? Especially the cost of kidney function tests is high?

The kidney function test package includes different small tests, to know exactly what tests you need to go through the initial diagnosis, from which doctors will specify each type of counter test.



If you suspect or find any abnormalities, you will likely have to undergo further diagnostic tests.

This also results in a different test cost per case. Besides, depending on the center or the hospital that conducts the test with modern equipment, the team of experienced doctors will have a price difference.

Currently, there are many reputable hospitals and testing centers nationwide to ensure that you can consult depending on the geographical area near where you live, convenient to move.

If you still have many questions and want to consult more carefully, you can also contact Diag's hotline 19001717, one of the leading prestigious medical diagnostic testing centers for advice and appointment.

We should test kidney function periodically every year or when there are abnormal signs that need the immediate hospital to be diagnosed promptly. Testing methods will help detect kidney diseases, thereby preventing dangerous complications affecting the health of each person.

Please find the nearby location or the nearest branch your home to visit for tests and get quick online results. For more detailed information about our test menu and price list, click here.

The site cannot and does not contain medical advice. The medical information is provided for general informational and educational purposes only and is not a substitute for professional advice. Accordingly, before taking any actions based upon such information, we encourage you to consult with the appropriate professionals.

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