Understanding renal function tests and it’s benefits

The Biomarker Handbook is a curated series that seeks to provide readers with insights on each biomarker we cover in our blood test packages and its relation to our body.


A healthy renal function is paramount to our wellbeing as, without it, our bodies would hardly be able to function. This is due to the kidney’s key purpose of filtering the blood to remove toxins and waste, as well as its role in producing hormones and monitoring the body’s PH balance and fluid levels.

Here is all you need to know about your kidneys, and the tests needed to ensure they remain healthy.

What is a Renal Function Test?

Renal function tests keep track of your kidney’s health and are usually conducted by tracking key biomarkers in the blood and urine. These three basic tests are as follows:

  • Blood Urea Nitrogen (BUN)—Urea is a waste product of the body’s protein assimilation, and nearly all kidney diseases trigger abnormally high levels of it in the blood. For this reason, a BUN test, in which levels of urea nitrogen are verified, may act as an early warning system for kidney disease. However, it should also be noted that other causes of elevated urea nitrogen levels are gastrointestinal bleeding and treatment involving steroids.
  • Creatinine—Another key indicator of kidney health is creatinine, which is formed by working muscles and excreted only by the kidneys. Creatinine levels in our bloodstream can be a reflection of our body’s glomerular filtration rate, making it an important biomarker when tracking your kidney health. Since kidney impairment is the only cause of imbalanced creatinine levels in the urine, it is a more specific determination of kidney function than a BUN test. This is as urea nitrogen levels can be influenced by factors other than kidney function.
  • Creatinine Clearance Rate (CCR)—By determining the efficiency at which the kidneys clear creatinine from the blood, renal health and function can be estimated. The test is performed over a 24-hour period in which urine and blood levels of creatinine are tested, along with urine volume. This can then be used to determine the rate per minute of blood (in millilitres), which can be cleared of creatinine. Low creatinine clearance is an indication of abnormal renal function.

Why Renal Function Testing is important

Not only can renal testing help determine your kidney efficiency and aid in the diagnosis of kidney disease, it may also aid your doctor to determine your state of hydration.

Additionally, since kidney disease is usually symptomless until it is too late, having irregularities documented and analyzed early becomes of critical concern when it comes to renal health.

Screening for kidney function with these three biomarkers needs to be a regular occurrence to ensure early detection of early kidney malfunction.

Symptoms to watch out for

While the symptoms of kidney disease may not be obvious, it is still important to take note of possible symptoms and conditions associated with it.

Visit your doctor if you feel/ experience:

  • Unexplainably cold all the time, even at a comfortable temperature
  • Constantly fatigued, weak, and distracted
  • Constantly foamy urine, which may indicate protein in the urine.

However, if you only experience occasional foaminess due to the velocity of urination, and your urine is flat most of the time, there is probably nothing to worry about.

  • Blood in the urine. This may be an indication of damaged kidneys, kidney stones, tumors, or infection, and should be dealt with immediately.
  • Swollen ankles, feet or legs. This may be caused by fluid retention within your body.
  • Chronic itching, which may be the result of waste left behind in the bloodstream.
  • Insomnia, which can be caused by unremoved waste in the bloodstream
  • Uncharacteristically frequent urination, especially during the night.

While some of these symptoms may be due to factors other than kidney ailments, they should still be followed up on with a complete renal analysis by your doctor.

What if your Biomarker levels are abnormal?

Many times, increased levels of creatinine or urea can be caused by a diet high in meat or protein or a lifestyle heavy in exercise.

Additionally, certain medications can also affect your levels of creatinine or urea. This is why it is crucial that you alert your doctor to all forms of medication that you are on.

With this information, they will be able to best determine the cause and treatment of abnormal levels of key biomarkers and prescribe any medications or further testing which are necessary.

Are there natural ways to return your results to normal?

Many times, abnormal results of a renal function test can be corrected through diet, exercise, and proper hydration.

For instance, a diet high in meat may cause BUN levels to rise, and a kidney infection or kidney stones can cause creatinine levels to rise as well.

BUN levels may also be affected by dehydration. With those who exercise more often and with a higher muscle mass usually showing higher creatinine levels than others.

In most of these cases, taking simple measures such as reducing the amount of meat and protein consumed and drinking more water, may be all it takes to get things back on track.

Consuming a diet rich in green leafy vegetables, nuts, legumes and other sources of electrolytes and alkali can help balance the body’s PH levels, which will also help keep your kidneys healthy.

What can your doctor do?

While the symptoms and treatment of kidney disease can vary with the type of disease, your doctor may have you do one or more of the following:

  • Treatment for diabetes
  • Use of blood pressure medication
  • Use of blood building medication for anemia
  • Diuretics, or other medications to reduce swelling of the hands and feet
  • Cholesterol-lowering medication
  • Dialysis
  • Kidney transplant

When should you see your doctor?

In addition to regular renal function testing as part of your annual exam, you should see your doctor immediately if you experience the following symptoms:

  • Foamy urine for extended periods (not just from urinary velocity)
  • Always feeling cold and/or tired
  • Swelling of the hands, feet, ankles and/or legs
  • You’re always itchy
  • You have chronic insomnia
  • There is blood in your urine
  • You urinate constantly, particularly at night

Any time any of these symptoms are experienced—especially for a long term—it is in your best interest to have your doctor perform complete renal function testing.

Other tests to consider

While BUN and creatinine testing is key when determining the presence of kidney disease and evaluating kidney function, there are some other tests to be considered as well:

  • A fasting blood glucose test can determine if there is any damage to the kidney’s blood vessels.
  • Testing for electrolytes and bicarbonate levels in the blood can help verify kidney function.
  • Blood tests for certain hormones can tell whether the kidneys are producing them as needed by the body.
  • Blood count to measure hemoglobin levels and red blood cells produced by the bone marrow, as well as iron studies, can reveal the existence of anemia.
  • Ultrasound testing can be used to reveal blockage of the kidneys, as well as other causes of kidney disease.
  • A duplex doppler study or angiogram can be used to determine problems due to restricted blood flow in the kidneys.
  • A kidney biopsy can be used either to determine the cause of chronic kidney disease or can be used after a kidney transplant to determine the body’s acceptance of the new organ.

Along with the crucial nature of our kidney’s function comes the need to monitor renal health through a variety of tests and biomarkers.

In addition to these tests, implement habits which are beneficial to your kidney’s health into your lifestyle. This includes making sure you consume adequate amounts of leafy greens and fluids, reduce your salt intake, and possibly reducing the amount of meat and/or protein in your diet.

However, if you start to notice any signs or symptoms of kidney disease, be sure to visit a trusted medical professional for more advice. Remember, kidney disease is not to be taken lightly, and ignoring signs of renal damage can spell disaster!



If you want to find out more about managing a vitamin B12 deficiency and how you can balance cobalamin levels, take a look at our lifestyle article here!

Interested in other biomarkers, check out the rest of The Biomarker Handbook.

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