Also called serum creatinine, creatinine clearance, CrCl · Reviewed
Definition:Creatinine is a normal waste product made when muscles are used and some muscle tissue breaks down. The kidneys filter it out of the blood into the urine, so MedlinePlus explains that it builds up in the blood when the kidneys are not working well. Blood creatinine is the number used to calculate eGFR.
Why one result is not the whole story
MedlinePlus says creatinine alone is not the best kidney test, because people make different amounts depending on muscle mass, diet, age and activity. That is why it is turned into eGFR, or into a creatinine clearance (CrCl) using a timed urine sample or a formula. Very muscular people, or those who have lost muscle, can have results that do not match their kidney function.
How labels use it
Fosamax is not recommended when creatinine clearance is under 35 mL/min.
Cialis once daily is not recommended when creatinine clearance is below 30 mL/min, and lower doses are used with reduced kidney function.
Farxiga and Jardiance say creatinine rises a little and eGFR falls in the first weeks, then settles, and the change reversed after stopping.
Reclast reported a temporary creatinine rise within 10 days of the infusion in 1.8% vs 0.8% on placebo.
Why it matters for your log
A creatine supplement or a hard workout the day before can nudge creatinine up. Noting those next to the lab date helps a clinician read a borderline result.
General education drawn from labels and published studies, not personal medical advice. Your prescriber, pharmacist and the label that came with your product are the final word.
It can mean the kidneys are not filtering well, but muscle mass, diet and exercise also change it. That is why it is usually turned into eGFR.
What is creatinine clearance?+
An estimate of how fast the kidneys clear creatinine, in mL/min, from a timed urine test or a formula. Labels such as Fosamax and Cialis use it to set kidney cutoffs.