What is Creatinine?

Creatinine is a byproduct of creatine which helps muscle to get the required energy. As creatine is a waste compound, it is no longer needed in body. So to maintain a healthy body, our body filters the creatinine from blood through the kidney. So, creatinine is removed through urine. This is the normal mechanism.

What is creatinine in blood test?

Creatinine test is a test that measures creatinine amount in blood and in urine. Both of these tests are useful to give an indication whether kidney is working perfectly or not. So creatinine test is essential to predict kidney functioning.

Creatinine Test Purpose

The purpose of creatinine test are the following

• It helps to predict that how well the kidney is functioning 
• It is an useful test for screening of suspected kidney problems 
• It helps to monitor the kidney problems
• It helps us to know the appropriate treatment for the patient
• It helps us to know the response of treatment
• It helps us to know the treatment outcome, progression of disease if occurred or not  and if any modification of ongoing treatment is needed or not
• It helps to determine the exact dose of medicine
• It helps to determine if any change of dose of medicine is needed or not 
• It gives an idea about the overall physical condition of patient
• It helps to calculate the estimated glomerular filtration rate (eGFR). eGFR gives us knowledge about how much effectively the kidney is filtering blood.
• It helps to monitor transplanted kidney functioning 

Creatinine Test Importance

Creatinine test helps to identify kidney issues before any signs or symptoms appear in body. Thus, people with high risk to develop kidney problems can go for the test for early diagnosis of any kidney problems.

Creatinine is a useful test when there is symptoms of kidney problems such as swelling of feet, difficulty in urination or any urinary changes, fatigue, loss of appetite, anemia, puffiness around the eye,etc. It is a very useful test during the evaluation of patient in emergency room. 

What Creatinine Test Measures

Creatinine test measures the total amount of creatinine in the blood or in the urine.

Creatinine is a byproduct during the metabolism of creatine. This creatinine is measured through the creatinine test.

Creatinine Test Types

Creatinine test can be of two types- serum creatinine test and urine creatinine test.

Serum creatinine test measures creatinine amount in blood.

Urine creatinine test measures the amount of creatinine in urine during 24 hours period.

All these measured values can be compared with the creatinine clearance test.

Creatinine Test Procedure

Creatinine test are of two types- blood creatinine test and urine creatinine test.

For blood creatinine test , blood is drawn from a vein ( preferably vein of arm) and this blood sample is analyzed for creatinine measurement. Based on this blood sample, creatinine test results are made.

For urine creatinine test, you need to collect all of your urine over a 24 hour period. For this purpose, a special urine collection container is needed. This urine will be analyzed for urine creatinine measurement. The test result will be prepared based on this urine.

24 hour urine collection test usually involves the following steps

1. Empty the bladder in the morning and flush the urine away.You need to record the time.
2. Now, for the next 24 hours, collect all your urine in the container
3. Store the collected urine in a cool place, for example- refrigerator 
4. Next, after collection of 24 hour urine, return it to the laboratory where test measurement will be done.

Creatinine Test Precautions

Follow your doctors instructions if any special precaution is needed before the test. Whether any special precautions needed is based on your underlying other medical conditions, the drugs you are taking and the diet you are taking.  

Special precautions are an individualized issue, not all who are going to do the test is needed to take precautions. But some people needs to take the precautions before going for the test.

The special precautions that one needs to follow before the test are usually the following 

1. Avoid to eat meat within 24 hours
2. In case where creatinine is tested in a panel, then fasting is required for up to 12 hours before the test.
3. Supplements, medicines, herbal products can affect test results. So, all medicines, supplements, herbal products should be reviewed before the test. You just need to follow your doctors instructions. Do not stop any medicine, supplements or herbal products without consulting with your doctor.
4. For urine creatinine test, you need to collect all of your urine over 24 hour period. To get accurate results, sample collection needs to be accurate, so do not waste your urine during urine collection in the container.

Normal Creatinine Levels

Blood Creatinine: 0.7 to 1.3 mg/dL for males and 0.5 to 1.1 mg/dL for females.

Urine Creatinine: 15- 25 mg/kg in 24 hours.

High Creatinine Levels

If creatinine level is above normal range it means that maybe kidney is not functioning properly, kidney is unable to filter out the creatinine present in blood.

High level of creatinine can also be seen in muscle diseases, dehydration and sometimes due to complications during pregnancy.

Usually high levels of creatinine in the blood and low levels of creatinine in the urine indicates kidney disease or other diseases that hamper kidney functions such as 

1. Autoimmune disease
2. Urinary tract blockage
3. Bacterial infection of kidney
4. Heart failure
5. Diabetes complications 

Creatinine Levels Low

When creatinine levels are lower than normal range, it is seen in

• malnutrition
• loss of muscle mass due to any conditions

Creatinine Test: Few Points To Note

Creatinine abnormal result doesn’t always mean that there is an existing kidney disease. The following conditions can elevate creatinine levels temporarily

1. Intense exercise
2. High meat consumption within 24 hour before the test
3. Pregnancy
4. Medicines that elevate creatinine level as side effects

But it is important to mention that normal range of creatinine level does not guarantee the proper health of kidney because when kidney problem is mild or moderate, it may not cause abnormal rise of creatinine levels.

Thus, in early stage of some kidney diseases, creatinine test may not give useful information about the health of kidney.

Creatinine Test Results Determining Factors

Following are the factors that affect creatinine test results

1. Muscle mass
2. Age
3. Diet
4. Drugs
5. Pregnancy

Body size and muscle mass- Creatinine is the byproduct of creatin which helps muscle to get energy. So,the creatinine level is dependent on muscle mass. Thus, creatinine test result can be affected or is less accurate in obese, bodybuilders, malnourished or amputees. In a simple term,less muscle mass will give low creatinine level and more muscle mass will give high creatinine level.

Age- People in their old age has less muscle mass. So, creatinine level can be low.

Diet- Consumption of meat can increase the level of creatinine. So, meat consumption within 24 hours before the test should be avoided.

Drugs- Certain drugs, herbal products, supplements, antibiotics can cause change of creatinine levels.

Pregnancy- Sometimes creatinine levels become low during pregnancy. But due to some complications of pregnancy, creatinine levels can elevate.

Do I need Creatinine Follow Up Test?

Based on the creatinine test result, it is decided if you need a follow up test or not. If test results are not within normal range, then you need a follow up test.

Your overall health condition, presence of other underlying medical conditions, how long you have kidney problems (whether it is recently diagnosed or present for years), your age- all these factors determine how many times you need a follow up test.

Creatinine test is usually done with other blood tests like RBC blood test, WBC blood test, Hemoglobin test, Platelet count test, other kidney function tests, etc.

In few cases kidney biopsy is needed, but this is not common and is not done routinely. 

Takeaway

Creatinine test is a part of routine test. There are many factors as mentioned above that can interfere to give accurate test results. Moreover, many times in early kidney disease creatinine test result may not show abnormal value. So, solely based on creatinine test result one should not conclude how healthy the kidney is.

Other tests are needed to confirm the health status of kidney. Creatinine test is helpful to some extent to give idea about the health of kidney, but not in all cases.