The kidneys excrete creatinine, a chemical substance that results primarily from metabolic changes in the muscles. In a healthy person, creatinine is excreted in the urine following the filtering process in the kidneys. Creatinine accumulates excessively in the plasma if the kidneys are not functioning properly.
What is creatinine?
It’s a chemical compound found in human blood and urine. Creatinine is produced as a byproduct of metabolic processes (primarily in the muscles) that break down creatine phosphate. The kidneys discharge it in the urine. Muscle mass is what determines its size. Creatinine is the fundamental tracer that allows you to monitor the function and health of the kidneys (see what tests best evaluate the work of the kidneys ).
Creatinine is found in the blood and urine and is used to test kidney function (for more information, see What Does Kidney Pain Mean?). For this indicator, your doctor may order blood and urine tests.
Blood creatinine standards
The average normal adult blood creatinine concentration is 0.6-1.4 mg/dL (or 53-115 µmol/L) .
However, creatinine values can be defined in more detail by dividing patients into 3 groups.
|Type of patients||standards|
|children under 5 years of age||21–36 µmol/L|
Urine creatinine standards
If tested on a urine sample, normal creatinine values for women are 0.74-1.57 g/day or 7-14 mmol/day and for men 1.04-2.35 g/day or 9-21 mmol/day.
These values may vary from lab to lab as different methods and apparatus may be used.
When is it worth examining?
Creatinine testing is a diagnostic test used to assess kidney function. We also frequently perform them in patients being treated for diseases that cause kidney dysfunction over time, such as hypertension or diabetes, as well as in cases of abnormal urine tests.
Before surgery and diagnostic tests that use a contrast agent, the level of creatinine should also be checked.
What does an elevated level mean?
Elevated blood creatinine levels are usually associated with worsening kidney function, but some drugs can also increase the level. However, not all abnormal results mean serious kidney damage, and it is up to the physician to interpret the results.
Creatinine level too low
Low concentration occurs in people who are malnourished, emaciated, with low muscle mass, in people with severe liver diseases.
It happens that pregnant women may have low creatinine levels. Also, taking certain medications, e.g. those with anti-inflammatory effects, may cause too low levels of this parameter in the blood.
What does the test look like?
Proper preparation for the test is essential if we want to obtain reliable, unfalsified results.
Creatinine – blood concentration test:
- the day before you should not do intensive sports,
- you need to go for the test on an empty stomach , i.e. do not eat anything for at least 8 hours (see what tests need to be done on an empty stomach ),
- The test consists in puncturing a vein and drawing blood
- the result is usually obtained after 24 hours.
In the case of urine creatinine testing, it can be performed in 2 ways: from a random, single urine sample or from a 24-hour urine collection.