Creatinine

Reference Range

Creatinine is critically important in assessing renal function because it has several interesting properties. In blood, it is a marker of glomerular filtration rate; in urine, it can remove the need for 24-hour collections for many analytes or be used as a quality assurance tool to assess the accuracy of a 24-hour collection.

The reference ranges for serum creatinine are listed below.

Adult:

Female: 0.5-1.1 mg/dL or 44-97 μmol/L (SI units)

Male: 0.6-1.2 mg/dL or 53-106 μmol/L (SI units)

Elderly: Reduced muscle mass may lead to lower values

Adolescent: 0.5-1.0 mg/dL

Child: 0.3-0.7 mg/dL

Infant: 0.2-0.4 mg/dL

Newborn: 0.3-1.2 mg/dL

Possible critical values: >4 mg/dL (indicates seriously impaired renal function)

The reference interval varies with race, ethnicity, and gender. As a result, one should look at the calculated eGFR (estimated glomerular filtration rate), as reported from the measured serum creatinine, to assess renal function.
The GFR can also be calculated from the creatinine clearance (see below).

Note that urine creatinine concentrations (mg/dL) vary depending on water intake (hydration status) and, therefore, are not very meaningful by themselves.

Table 1. Glomerular Filtration Rate
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