Home › Lab tests › Creatinine

Creatinine

Kidney Function · also called Serum creatinine, Cr

What it measures

Creatinine is a waste product released at a fairly steady rate from muscle and cleared by glomerular filtration. It is the standard blood test for kidney function and is used to calculate eGFR and adjust drug doses.

Specimen and preparation

Specimen: Serum or lithium-heparin plasma
Tube: Gold top
Preparation: Avoid cooked meat for 12 hours before testing where possible.

Reference range

Group	Range
Adult male	0.7–1.3 (62–115) mg/dL (µmol/L)
Adult female	0.5–1.1 (44–97) mg/dL (µmol/L)
Child	0.3–0.7 (27–62) mg/dL (µmol/L)

Reference ranges differ between laboratories, methods and populations. Always use the range printed on your own lab report.

Causes of high values

Acute kidney injury
Chronic kidney disease
Urinary obstruction
Dehydration
Rhabdomyolysis or high muscle mass
Drugs blocking tubular secretion (trimethoprim, cimetidine)

Causes of low values

Low muscle mass (elderly, amputees)
Pregnancy
Liver disease with wasting

Method

Enzymatic (creatininase) or IDMS-traceable Jaffe (alkaline picrate) method

Good to know

Creatinine rises only after substantial GFR loss; a doubling roughly means halving of GFR. Jaffe methods are affected by bilirubin, ketones and some cephalosporins.

📱 Practise with a timer, track your score and earn certificates in the free MLT Globe app – Google Play or practise online.