Creatinine clearance: what it is, what it tells you and when it’s tested

Creatinine clearance shows how much blood your kidneys clear of creatinine in a minute. It is a measure of how well your kidneys filter. It needs all your urine from a full day and a blood test.

When it’s tested

Doctors order it when the eGFR, the estimate calculated from blood creatinine, may be wrong. For example in people with a lot of muscle or very little, on a special diet or after an amputation.

It is also used to set the dose of some medicines, and to follow some kidney diseases over time.

It is not a routine test. Collecting a full day of urine is a hassle, and missing a single pass of urine gives a wrong result. To check the kidneys of people who feel well, creatinine, eGFR and urine albumin are usually enough. That is why Rosa does not test it, but measures those three.

What it tells you, and what it does not

It shows how well your kidneys filter, measured rather than estimated. It helps when the eGFR estimate is not reliable.

It tends to come out a little higher than the truth, though, because the kidneys get rid of a bit of extra creatinine on top of what they filter. And if the urine collection is incomplete, the value comes out lower than the truth.

It does not say why the kidneys filter less, and it does not pick up albumin leaking into the urine.

That is why it is read together with other tests:

• Creatinine: It is needed to calculate the clearance
• eGFR: The estimate of filtration, with no urine collection
• Urine albumin: It picks up kidney damage that filtration does not show
• Cystatin C: Another filtration estimate that does not depend on muscle
• Proteinuria: Often measured from the same urine collection

Normal creatinine clearance levels

The lab decides what is normal. A common range is 97 to 137 mL/min for men and 88 to 128 mL/min for women. Other labs use lower limits, especially with age.

Clearance falls a little with age even in healthy people. Some reports adjust it for body size, and then the unit is mL/min per 1.73 m².

Your doctor mostly looks at whether it is below 60, and whether it stays low over time.

What your result means

Find the row for your result, in mL/min. Which values need a doctor? Below the limit on your report; below 30, soon.

• Below 15: Very low. Your kidneys filter very little. This is the level of kidney failure. It needs a doctor straight away, usually a kidney specialist.
• 15 to 30: Low. Your kidneys filter much less than normal. See your doctor soon: they usually refer you to a kidney specialist.
• 30 to 60: Reduced. Your kidneys filter less than normal. It can be real, or an error in the urine collection. Talk to your doctor: they usually repeat the tests and check urine albumin.
• 60 or more: Usually enough. Your kidneys usually filter enough. The lab sets the lower limit of normal, and it falls with age. Compare it with the range on your report. If it is below, talk to your doctor.

If your clearance is low or high

• Low creatinine clearance: Your kidneys filter less, or the urine collection was incomplete. Your doctor usually repeats the tests before deciding.
• High creatinine clearance: It happens in pregnancy, with a lot of protein in the diet or early in diabetes. Sometimes it is a collection error.

How to collect 24-hour urine

The lab gives you the container and the instructions. It usually goes like this:

• In the morning, pass urine in the toilet as usual and note the time: the collection starts now.
• From then on, collect all your urine in the container, day and night.
• The next morning, at the same time, pass urine into the container one last time: the collection is done.
• Keep the container cool, as the lab says, and bring it in the same day. The blood test is usually done that morning.
• If you forget to collect even once, tell the lab: it is better to start again another day.

What can skew the result

Clearance is sensitive to many things. It helps to know them before the collection.

• An incomplete collection: The most common error. The value comes out lower than the truth.
• A meat-heavy meal: Cooked meat raises creatinine for a few hours. Eat as usual, without excess.
• Very hard exercise: On the day of the collection, avoid very hard training.
• Some medicines: Some change how the kidneys get rid of creatinine. Do not stop them on your own: tell your doctor.

When to worry

Talk to your doctor if:

• Your clearance is below the limit on your report.
• It is below 60, or falls from one check to the next.
• It is below 30: see your doctor soon.
• Your urine is very foamy, there is blood in it or your ankles are swollen.
• You pass very little or no urine for many hours, with swelling or breathlessness: call 112 or go to the emergency department.

Frequently asked questions

What are normal creatinine clearance levels? A common range is 97 to 137 mL/min for men and 88 to 128 mL/min for women. Many labs use lower limits with age. The range on your own report is what counts.

How is creatinine clearance calculated? The lab compares the creatinine in a full day of urine with the creatinine in your blood. There is also a formula that estimates it from blood alone, with age and weight, often used to set medicine doses.

What does low creatinine clearance mean? That your kidneys filter less, or that the urine collection was incomplete. Your doctor usually repeats the tests and checks urine albumin before drawing conclusions.

What is the difference between clearance and eGFR? Clearance is measured with urine, eGFR is calculated from blood. eGFR is simpler and usually enough. Clearance helps when the estimate may be wrong.

Does Rosa test creatinine clearance? No. Rosa measures creatinine, eGFR and urine albumin, which are enough to check the kidneys in most people. If your doctor wants a clearance, they order it separately.

Sources

• KDIGO clinical practice guideline for the evaluation and management of chronic kidney disease. Kidney International, 2024. PMID 38490803
• Cockcroft and Gault, prediction of creatinine clearance from serum creatinine. Nephron, 1976. PMID 1244564
• MedlinePlus, US National Library of Medicine: creatinine clearance test. MedlinePlus, US National Library of Medicine