When and why

This test measures kidney function and is usually carried out when either the results of certain blood tests suggest an underlying kidney disease or as part of the monitoring of a drug treatment which has possible toxic effects on the kidney (such as foscarnet).

Over a 24-hour period all urine passed is collected in a bottle and then sent to the laboratory together with a blood sample taken at the same time to measure how well a substance called creatinine is excreted by the kidneys.

How it will help

This test provides information on how well the kidneys are working. If they are damaged, this knowledge can help determine whether a dose of a drug should be altered or discontinued.