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Kidneys and electrolytes · Urine
Creatinine (urine)
Creatinine in urine is usually not a goal in itself, but a correction value that makes other urine tests comparable.
At a glance
- Measured in urine
- In 1 test panel
- No special preparation
Explanation
Creatinine (urine): what is measured?
The analysis measures how much creatinine is in the urine. Creatinine is a waste product that is released from the muscles at a fairly steady rate and is excreted by the kidneys. Because this production is fairly constant per person, the creatinine level shows how concentrated or how dilute a urine sample is. This allows another substance in the same sample to be expressed per unit of creatinine, so the result no longer depends on how much you have drunk.
What can it detect?
- How concentrated or dilute a urine sample is, as a correction for other tests in the same urine
- Whether a 24-hour collection is complete
- Together with creatinine in blood: the creatinine clearance, a measure of how well the kidneys work
Result
What does the result mean?
Creatinine (urine) too high
A high value in a single sample usually means the urine is concentrated, for example because you have drunk little or collected the morning urine. People with a lot of muscle mass excrete more creatinine than people with little muscle mass; eating a lot of meat can also raise the value. In a 24-hour collection, a high amount fits a lot of muscle mass. A high value on its own is not a sign of disease.
Creatinine (urine) too low
A low value in a single sample usually means dilute urine, for example after drinking a lot. With little muscle mass, for example in older people, with long-term bed rest or after an amputation, excretion is persistently lower. In a 24-hour collection, a low amount can also mean that not all urine was collected; the collection is then not usable. A low value on its own is not a sign of disease.
After an abnormal result
With an abnormal albumin-creatinine ratio, the GP repeats the measurement and has the eGFR measured in blood. A urine creatinine that is abnormal on its own usually only calls for attention to the way the urine was collected.
Reliability
How reliable is the test?
Creatinine in urine has virtually no diagnostic value on its own; its meaning lies in the combination. The Dutch GP guideline (NHG) on chronic kidney damage uses the ratio between albumin and creatinine in urine to detect kidney damage, and the Dutch Society for Clinical Chemistry (NVKC) describes creatinine clearance as a combination of urine and blood creatinine. As a single result, the number mainly says something about how dilute the urine is and about muscle mass, not about a condition.
What can affect the result?
- The value depends strongly on fluid intake; without correction, a single sample is not comparable with another sample.
- Muscle mass, age, sex and eating meat affect the excretion.
- If a 24-hour collection is incomplete, both the creatinine value and every other test in that urine are wrong.
- For estimating kidney function, the eGFR from blood is more suitable; it does not need a urine collection.
Who it is for
Who is the test useful for?
Useful for
Useful as part of another test in the same urine, for example the albumin-creatinine ratio or when correcting the excretion of a mineral or other substance. As a single result, creatinine in urine has no meaning for someone without symptoms. If you want to know how your kidneys work, the eGFR from blood is more useful.
How common is it?
Chronic kidney damage is common, especially at older ages and with diabetes and high blood pressure. Kidney damage can be recognized by the eGFR from blood and the albumin-creatinine ratio in urine, not by creatinine in urine alone.
NHG guideline on chronic kidney damage and NIVEL primary care registrations
Drawbacks and risks
- A single value can wrongly be read as a measure of kidney function, while that requires the eGFR from blood.
Get tested
Creatinine (urine): test panels
Creatinine (urine) is part of these test panels. You order online and have your blood drawn at a collection point or collect the sample at home.
Evidence
Sources
This explanation is based on Dutch guidelines and independent information. It is general information, not a diagnosis. Discuss an abnormal result with your GP.
More about risks and resultsMore explanations
Other tests: Kidneys and electrolytes
- BUN/creatinine ratio
- Chloride
- CO2 (bicarbonate)
- Creatinine
- Cystatin C
- eGFR
- Phosphate (inorganic)
- Potassium
- Sodium
- Urea
- Urea nitrogen (BUN)