How is it used?
It is used to determine whether your kidneys are functioning normally. A calculation based on the serum creatinine concentration, called the eGFR (estimate of glomerular filtration rate) measures how effectively your kidneys are filtering small molecules like creatinine out of your blood.
Urine creatinine may also be used with a variety of other urine tests as a correction factor. Since it is produced and removed at a relatively constant rate, the amount of creatinine in urine can be compared to the amount of another substance being measured. Examples of this are when creatinine is measured with protein to calculate a urine protein/creatinine ratio (UP/CR) and when it is measured with albumin to calculate microalbumin/creatinine ratio (also known as urine albumin/creatinine ratio, UACR). These tests are used to evaluate kidney function as well as to detect other urinary tract disorders.
When is it requested?
Creatinine may be part of a routine blood test, widely used when someone has non-specific health complaints, or when your doctor suspects kidney problems. Creatinine and the eGFR are also used to monitor treatment of kidney disease or to monitor kidney function while you are on certain drugs.
What does the test result mean?
Increased creatinine levels in the blood suggest diseases that affect kidney function. These can include:
- glomerulonephritis (swelling of the kidney's blood vessels)
- diabetic kidney disease (the filters clog up with a proteinaceous substance)
- pyelonephritis (pus-forming infection of the kidneys)
- acute kidney injury (death of cells in the kidney's small tubes)
- urinary tract obstruction (e.g. prostate disease or kidney stones)
- reduced blood flow to the kidney due to shock, , congestive heart failure, , or complications of diabetes.
Creatinine can also increase as a result of muscle injury. Reduced levels of creatinine are not common and are not usually a cause for concern. As creatinine levels are related to the amount of muscle the person has, low levels may be a consequence of decreased muscle mass (such as in the elderly), but may also be occasionally found in advanced liver disease.
Male 60-110 µmol/L
Female 45- 90 µmol/L
0 day to <1 week 22-93 µmol/L
1 week - 4 weeks 17-50 µmol/L
4 weeks - 2 years 11-36 µmol/L
2 years - 6 years 20-44 µmol/L
6 years - 12 years 20-32 µmol/L
12 years -15 years 35–83 µmol/L
15 years - 19 years 50–100 µmol/L
19 years - 60 years 60–110 µmol/L
12 years to 15 years 35–74 µmol/L
15 years to 19 years 38–82 µmol/L
19 years to 60 years 45–90 µmol/L
The reference intervals shown above are known as a harmonised reference interval. This means that eventually all laboratories in Australia will eventually use this same interval so wherever your sample is tested, the reference interval should be the one shown above. Laboratories are in the process of adopting these harmonised intervals so it is possible that the intervals shown on the report of your results for this test may be slightly different until this change is fully adopted. More information can be found under Reference Intervals – An Overview
Is there anything else I should know?
Since creatinine levels are in proportion to muscle mass, women tend to have lower levels than men.
In general, creatinine levels will stay the same if you eat a normal diet. However, eating large amounts of meat may cause short-lived increases in blood creatinine levels. Taking creatine supplements may also increase creatinine.
There are a few drugs that interfere with the creatinine test, although there are some drugs that can cause some impairment in kidney function. Your creatinine levels may be monitored if you are taking one of these drugs.