24-hour urine creatinine test: what the result means
500–2,000 mg/day, converted (×0.00884)
- Updated
- 2026-09-10
- Every number with its source
What this test is
Creatinine is a substance that forms continuously in muscle as creatine is broken down, and it is removed from the blood almost solely by the kidneys. Because its amount depends mostly on muscle mass and is fairly constant from day to day, creatinine is considered a reliable marker of kidney filtration function. By measuring creatinine not in a single blood sample but in all the urine collected over 24 hours, doctors get a more accurate picture, because creatinine excretion over a short period can fluctuate. This test is often done together with the amount of creatinine in blood — their ratio makes it possible to calculate creatinine clearance, which shows how much blood the kidneys clear of this substance each minute. Per MedlinePlus, if kidney function is impaired, the amount of creatinine in urine usually falls, because the kidneys are no longer able to remove it effectively.
Reference range (MedlinePlus)
| Group | Range, mmol/day | Source |
|---|---|---|
| Adults (24-hour urine) 500–2,000 mg/day, converted (×0.00884) | 4.4–17.7 | MedlinePlus Reviewed 2025-07-01 |
Per MedlinePlus, the range for adults is about 500–2,000 mg per day, that is roughly 4.4–17.7 mmol per day. The exact interval depends on the laboratory's methodology, so what matters most is to go by the reference limit stated on your own result sheet.
When it is tested
- When impaired kidney function is suspected and how efficiently the kidneys filter the blood needs to be assessed
- Together with the amount of creatinine in blood — when calculating creatinine clearance
- To monitor a known kidney disease over time, so that any change in function can be seen
- To assess whether the 24-hour urine collection was carried out properly (creatinine is used as a check on how complete the collection was in other 24-hour urine tests)
- When muscle mass or protein metabolism needs to be assessed indirectly
How to prepare
- Urine is collected for a whole day (24 hours) into a special container, following the laboratory's instructions — the first morning urine is usually not included, while the next day's morning sample is included
- Your doctor may ask you to stop temporarily any medicines that could affect the result (for example some antibiotics or medicines that reduce stomach acidity) — always decide this together with your doctor, and never stop a medicine on your own
- It is worth keeping to your usual diet and fluid intake, unless your doctor tells you otherwise, because an unusually large amount of meat can affect the result
A raised result
A raised creatinine in urine is most often considered part of normal physiological variation rather than a sign of kidney disease. The main reasons are a large amount of meat in the diet before or during the collection day, and the breakdown of muscle tissue. Because creatinine is produced by muscle, people with a larger muscle mass usually have higher readings.
- A large amount of meat (especially red meat) in the diet during the collection period
- Breakdown of muscle tissue (for example after intense physical activity or an injury)
- A large muscle mass compared with the average population
Usually considered alongside a raised result:
- Whether the 24-hour urine collection was carried out completely accurately — losing part of the sample distorts the result
- The diet on the day of the test — whether there was an unusually large amount of meat
- Blood creatinine and creatinine clearance together — for a fuller picture of kidney function
- Discussing the result with a doctor in the context of the specific clinical situation
A reduced result
A reduced creatinine in 24-hour urine is, per MedlinePlus, linked to disorders of kidney function — from a reduced blood supply to the kidneys through to kidney failure. Because creatinine is removed from the body almost solely by the kidneys, when their function weakens they are no longer able to excrete it effectively into the urine, so the amount in urine falls.
- Impaired kidney function or kidney failure
- A reduced blood supply to the kidneys
- A urinary tract infection
- A urinary tract obstruction (a blockage)
Usually assessed alongside a reduced result:
- Blood creatinine and the calculated creatinine clearance — to refine the kidney filtration rate
- Urine sediment microscopy and a general urine test, to rule out a possible infection or inflammation
- Imaging tests, if a urinary tract obstruction is suspected
- Discussing further monitoring and the possible causes with a doctor
Full site in Lithuanian: proactiva.app
Frequently asked questions
›What is the normal creatinine level in 24-hour urine?
Per MedlinePlus, the range for adults is about 500–2,000 mg per day, that is roughly 4.4–17.7 mmol per day. The exact interval depends on the laboratory's methodology, so what matters most is to go by the reference limit stated on your own result sheet.
›How does creatinine in blood differ from creatinine in 24-hour urine?
Creatinine in blood shows the momentary concentration in a single sample, while the 24-hour urine test shows how much creatinine the kidneys removed over the whole 24-hour period. Both are used together to calculate creatinine clearance — it reflects kidney filtration function more accurately.
›Why can creatinine in urine be reduced?
Per MedlinePlus, a reduced amount is linked to impaired kidney function, a reduced blood supply to the kidneys, a urinary tract infection or an obstruction — because the kidneys are no longer able to remove creatinine effectively from the blood into the urine.
›Can diet affect the amount of creatinine in urine?
Yes. A large amount of meat, especially red meat, during the collection period can temporarily raise the result, because creatinine also enters the body partly with food. That is why your doctor may ask you to keep to your usual diet on the day of the test.
›How is the 24-hour urine sample collected correctly for this test?
Urine is collected for the whole 24 hours into the container given by the laboratory, following its instructions; the first morning urine is most often not included, while the next day's morning sample is included. Losing part of the sample distorts the result, so it is important to follow the exact instructions.
›Do medicines need to be stopped before this test?
Your doctor may ask you to stop temporarily certain medicines, for example some antibiotics or medicines that reduce stomach acidity, because they can affect the result. Always agree any stopping of a medicine with your doctor, and never do it on your own.
Sources
Related markers
This site is not an emergency service. If severe chest or head pain, breathlessness, confusion, difficulty speaking, heavy bleeding or another acute problem has come on suddenly — do not wait for tests, call 112.
This information is not a diagnosis and does not replace a consultation with a doctor. Reference ranges depend on the laboratory, your age and sex — always compare your result with the range printed on your own report.