What is Creatinine?
Creatinine is produced continuously and cleared by the kidneys. Levels are influenced by muscle mass, hydration, and sometimes diet or supplements. This is why creatinine is typically interpreted together with eGFR, and trends are often most informative.
Why is Creatinine relevant?
Creatinine is produced continuously from muscle breakdown and is filtered out of the blood by the kidneys — so the value says something about both kidney function and muscle mass. People with a lot of muscle naturally have slightly higher creatinine, and that is not a problem; people with low muscle mass often have lower values. For assessing kidney function you therefore always look at the combination with eGFR and context.
How to read Creatinine in context
Creatinine is almost always interpreted together with eGFR, plus context on age, sex, and muscle mass. Recent intensive training, high protein intake, or creatine supplementation can temporarily raise the value — for a fair measurement, wait a few days after heavy effort. Trends across measurements give the best picture of actual kidney function.