Serum creatinine

Before you rely on it

What to check

Interpret it with a clinician, alongside the equation used and any other markers.

The common error

Where people go wrong with serum creatinine

Reading a single out-of-range value as a diagnosis. Trend and context are what matter, and a one-off result taken after a hard training week can look alarming and mean nothing.

Worked through

Serum creatinine in plain numbers

A lab report lists creatinine in milligrams per deciliter or micromoles per liter. To convert, multiply mg/dL by 88.4: a result of 1.0 mg/dL is 88.4 µmol/L. Reference ranges differ between laboratories and between men and women, and typically sit somewhere around 0.6 to 1.3 mg/dL, so the printed range on your own report is the one to read; the value feeds an equation that also uses age and sex to estimate filtration. Clinicians look at change over time: a sudden rise of a few tenths of a mg/dL within a couple of days can be a warning sign, while a slowly drifting number needs a different kind of follow-up; the numbers are illustrations, not a reading of anyone's results.

Easily confused

Serum creatinine and its neighbours

Serum creatinine is not the same as eGFR, BUN or cystatin C. Creatinine is a muscle waste product in the blood. eGFR is an estimate of filtering rate computed from creatinine. BUN, blood urea nitrogen, is a different waste marker affected by diet and hydration. Cystatin C is another marker that does not depend on muscle mass, sometimes used alongside. Urine creatinine and creatinine clearance are separate tests; each tells part of the story, and clinicians combine them with urine protein and the clinical picture.

In real decisions

Where serum creatinine turns up

Doctors order it in routine panels to screen kidney function, to monitor chronic conditions such as diabetes and high blood pressure and to adjust dosing of some medicines; it is checked in hospital patients and after contrast imaging; people use calculators to understand the equation behind their eGFR. Repeated measurements track whether kidney function is stable. Discussing the trend with the clinician gives context that a single value cannot.

Know the edges

Where serum creatinine stops being reliable

Creatinine depends on muscle mass, diet, hydration and some medicines and supplements, so a normal or abnormal value can be misleading; it rises late in kidney damage. Reference ranges vary by lab. This page is educational and is not medical advice or a diagnosis, and anyone with concerns about their results should discuss them with a qualified clinician.

Quick answers

What people ask about serum creatinine

What can raise creatinine besides kidney disease? Dehydration, heavy meat meals, intense exercise, high muscle mass, creatine supplements and some medicines can raise it. A clinician considers these when interpreting results.

Should I fast before the test? Instructions vary. Ask the lab or your clinician, since some panels require fasting and creatinine alone usually does not.

What is cystatin C? Another blood marker of kidney function that does not depend on muscle mass. Clinicians sometimes use it with creatinine for a more accurate estimate.