Creatinine [Creat]

This is the best routine blood test for measuring how well kidneys are working. It is produced by muscles and put out by the kidneys. Because it is produced by the muscles, it tends to be higher in muscular people, so that a weightlifter with normal kidney function will have more creatinine in their blood than a little old lady. Normal = 60-120 micromol/litre (0.7-1.4 mg/dl).

less than 60
Suggests a very small person, or someone with little muscle (including children).
'Normal' - but there could still be reduced kidney function (see below)
Mild to moderate kidney failure - but in someone with little muscle, 200 could sometimes mean more severe kidney failure.
Moderate to severe kidney failure.
Most dialysis patients have creatinine measurements over 300 all of the time.

Creatinine measurement methods vary, so the same blood samples may give slightly different results in two different labs. They also vary from day to day.

This means that small % changes in Creatinine do not mean much unless they are part of a trend. Sometimes you need to repeat the test to be sure.

A problem with Creatinine tests is that levels do not rise much in early kidney disease - they may be normal until more than 50% of kidney function is lost in some people. Ways to get round this include using creatinine along with other things (e.g. age) to estimate GFR - eGFR gives an approximate % kidney function, and is returned automatically on many samples sent for creatinine measurement. Creatinine Clearance is a more difficult measurement of kidney function that requires a 24 hour urine collection.

More info about Creatinine from Lab Tests Online

More info about tests of kidney function from EdRen..


This page created 6th December 2004, last modified July 7, 2015, on the PatientView website